Patent Description:
One of the subgroups of electronically commutated motors are brushless D. Brushless D. motors are well known and used in a range of devices. Brushless D. motors typically include permanent magnets coupled to or on a rotor and windings formed on a laminated stator that form electromagnets when current is applied to the stator. High energy permanent magnets used in motors may be made from materials which include rare earth metals such as samarium-cobalt and neodymium-iron-boron. However, such permanent magnets are expensive resulting in a higher cost motor. Furthermore the availability of these rare earth metals is limited. To reduce costs other forms of brushless D. motors that do not require permanent magnets or windings associated with the rotor were developed.

Another class of electronically commutated motors that do not include permanent magnets are called switched reluctance (SR) motors. Switched reluctance motors run by creating reluctance torque, which is proportional to the difference of aligned and non-aligned values of the self-inductance in the SR motor. Conventional SR motors comprise concentrated windings in the stator that produce torque due to the self-inductance variation slope of one phase and the positive DC current applied to that phase. The inductance ratio between the aligned inductance and the unaligned inductance is important in generating torque and may vary in the range of <NUM>-<NUM>. Consequently SR motors are used for the applications where the input power level exceeds several hundred watts and are generally larger motors with stator outer diameters greater than <NUM>. Such prior art SR motors have been used to drive devices such as automotives, vacuum cleaners and washing machines and other large applications. They have not been suitable for driving low power (less than a hundred watts) or small (stator outer diameters less than <NUM>) high speed devices (up to <NUM>,<NUM> rpm) due to the failure to produce enough torque in a small arrangement having low inductance ratios. SR motors have also been used in conditions where severe environmental conditions occur such as in high or low temperatures.

The stators of SR motors are generally wound with three, four or five phases in a concentrated winding arrangement. Typically a SR motor has less rotor poles than stator poles. <FIG> shows an example of a three phase SR motor stator and rotor arrangement. The three phases are made up of three groups of concentrated windings: 10a, 10b, 10c, and 10d form a first phase; 12a, 12b, 12c and 12d form a second phase; and 14a, 14b, 14c and 14d form the third phase. In such a concentrated arrangement a coil with sides 10a and 10b, is wound around a stator tooth or pole <NUM> of the stator <NUM>, thus the windings are concentrated around one stator tooth <NUM>. The rotor <NUM> is formed of a soft magnetic material, for example laminated silicon steel, and includes salient magnetic poles <NUM> to create a difference in magnetic reluctance between rotor and stator along the poles and between the poles.

Generally SR motors have been driven by applying current to energize a single stator phase at one time and switching the current between stator phases to cause rotation of the rotor. A flux is generated through the energized stator poles and the rotor poles, which pulls the rotor poles towards and into alignment with the energized stator poles. Switching the current to a second adjacent stator phase results in the pulling of the rotor poles to align with the second stator phase. The continuous switching of the current in a sequence to adjacent stator phases around the stator results in rotation of the rotor. Controlling the timing of the current switching controls the continuity of the rotor rotation. Switching the current at the optimum position of the rotor is desired to reduce torque ripple or cogging as the rotor rotates. Torque ripple may result in vibration and noise within the motor. In attempts to reduce torque ripple the current being applied to adjacent phases during the switching step has been overlapped. However, when current is applied to two phases of a conventional SR motor in synchronism the motor is less efficient, as there is no significant increase in torque despite twice the power input being provided.

In such SR motors one rotor pole is generally configured to align with a single stator pole when the rotor is pulled into alignment with the energized stator pole. For example as seen in <FIG>, when stator phase <NUM>, including stator coil sides 10a & 10b and 10c & 10d have been energized the rotor poles, 32b and 32c are pulled to align with stator teeth <NUM> and <NUM> respectively. Consequently the normal or radial components of the electromagnetic forces are applied to stator teeth and rotor poles. Such radial forces may be relatively high and can be a source of vibration and noise within the motor.

Some efforts have been made to reduce the motor noise produced by SR motors. For example <CIT> describes a multiple phase SR motor comprising a stator with concentrated windings and multiple rotor poles. Each of the stator poles and the rotor poles may comprise multiple teeth. The stator includes at least one redundant pole set for each motor phase to help distribute ovalising forces on the motor assembly as it rotates and reduce motor noise. <CIT> suggests reducing the torque ripple effect by using rotor poles having <NUM> wide rotor poles and <NUM> narrow rotor poles. The three phase reluctance motor has concentrated windings and includes <NUM> stator poles with the <NUM> rotor poles. During each energization phase, where one phase is energized at a time the rotor is sequentially advanced such that the leading edge of a wide rotor pole interacts with a first energized stator pole and then a narrow rotor pole is drawn into alignment with a second energized stator pole of the same phase. However, to enable significant torque to be produced from such arrangements these SR motors would be required to be relatively large to maintain an inductance ratio of approximately <NUM> with the increased number of stator poles.

<CIT> is said to provide a SR motor producing increased torque and efficiency. The SR motor comprises a stator having evenly spaced concentrated winding poles and a rotor with unevenly spaced rotor poles. Two adjacent phases are energized at all times in order to provide controlled rotation of the rotor. The adjacent windings are coiled in a direction about the poles of the stator in a manner that causes the polarity of the stator poles to have opposite polarities when the pair is energized with a current so as to create a magnetic circuit between the poles of each pair. The pairs of adjacent stator poles align with half (e.g. <NUM>) of the rotor poles and when the next pair of adjacent stator poles are energized these align with the other half (e.g. further <NUM>) of the rotor poles. Such a SR motor arrangement would not be suitable for use in high speed small devices.

Chinese Patent Publication no. <CIT> is said to describe a permanent magnet switched reluctance motor adopting a distributed winding. The stator adopts a three-phase armature winding with a distributed structure, only one winding coil is arranged between adjacent stator tooth slot bodies, coils which pass over two stator slots are connected together to form a winding of one phase. A permanent magnet is also embedded into the stator. The ratio of the number of the stator teeth to the number of the rotor teeth is <NUM>:<NUM>, and the number of their poles is in the form of <NUM>/<NUM> or <NUM>/<NUM>.

There is further need to reduce one or more of the noise, vibration and/or size of SR motors if they are to be used in medical devices and/or conditions where low noise is important, such as during sleep.

Motors are used to drive a variety of devices in a diverse range of applications including but not limited to fans, pumps, medical devices, automotive industry, aerospace, toys, power tools, disk drives, and household appliances. Motors have been used in medical devices to generate a supply of pressurized gas for example in Positive Airway Pressure (PAP) devices and ventilators. These devices generally include permanent magnet brushless D. SR motors generally have not been used in such devices due to the generally larger size and higher level of noise of SR motors.

The noise produced by some medical devices is required to be relatively low so as not to disturb the user. In particular for medical devices that may be used for long periods of time, such as throughout the day, and/or during sleep, such as PAP devices and/or ventilators the level of noise emitted is a significant issue. Sound pressure values of a variety of objects are listed below:.

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<CIT>
relates to a redundant switched reluctance motor. <CIT> relates to an electrical machine comprising a rotor without windings, a stator having an armature winding and a field winding for generating a magnetomotive force in a direction extending transversely of the magnetomotive force generated by the armature winding. <CIT> relates to a tool including a drive shaft, an electrical machine drive system, an electronic controller and a gear system. The drive system includes a rotor and a stator arranged around the rotor. The rotor includes a plurality of laminated sheets attached to a motor shaft, each sheet being generally perpendicular to a longitudinal axis of the motor shaft and having a pattern of regions of relatively high magnetic permeability interspersed with regions of relatively low magnetic permeability. The stator includes electrical windings dispersed in slots disposed around an inner surface of the stator, the slots extending generally parallel to the motor shaft such that, when current flows in the windings, a stator magnetic field generated by the current has the same number of magnetic poles as there are regions of high permeability on the rotor. The electronic controller is configured to control the current flow in the stator windings to cause the stator poles to rotate in synchronism with rotation of the motor. The gear system is connected to the motor shaft and the drive shaft for transferring torque to the drive shaft. <CIT> relates to an electric rotating machine including a stator, a rotor, and a plurality of magnetic shields. The stator includes a stator core and a stator coil wound on the stator core. The stator core has a plurality of stator teeth arranged in the circumferential direction of the stator core. The rotor includes a rotor core that has a plurality of magnetic salient poles formed therein. The magnetic salient poles face the stator teeth through an air gap formed therebetween. Each of the magnetic shields is provided, either on the forward side of a corresponding one of the stator teeth or on the backward side of a corresponding one of the magnetic salient poles with respect to the rotational direction of the rotor, to create a magnetic flux which suppresses generation of a negative electromagnetic force that hinders rotation of the rotor. <CIT> describes a rotor comprising two poles of salient poles, wherein coils are wound around slots of fixed armatures, and armature coils for the first, second and third phases are formed, a switching transistor is connected to the armature coil of each phase, and current application control is performed by position detection signal. <CIT> describes that in two sets of three-phase armature coils, <NUM> slots 3a, 3b,. , 3x are arranged and installed at equal separation intervals on the inner circumferential face of a fixed armature <NUM>. On the other hand, four salient poles 1a, 1b, 1c, 1d in a width of <NUM> deg. each (electrical angle) are arranged and installed alternately on the outer circumferential face of a rotor <NUM> at three separation intervals and in widths of four separation intervals of the slots 3a, 3b,. , 3x for the fixed armature <NUM>. Then, energization whose phase difference is at <NUM>/<NUM> or <NUM>/<NUM> of the slot separation intervals is made for the armature coils of two phases. Then, the relative positions of the slots 3a, 3b,. , 3x are shifted by <NUM>/<NUM> of their separation intervals by tip ends 1A and 1C as well as 1b and 1D in the directions of rotation of the salient poles 1a, 1b, 1c, 1d, and torque ripples are offset. <CIT> relates to a doubly-fed switched reluctance machine in which at least two sets of phase winding are energized to produce desired output torque.

Claim <NUM> defines a method as described lower in the text.

The present technology is directed towards switched reluctance motors and devices that comprise such switched reluctance motors.

A first aspect of the present technology relates to switched reluctance motor comprising a stator having a distributed winding configuration.

Another aspect of the present technology relates to switched reluctance motor having higher total torque and distributed force.

Another aspect of the present technology relates to switched reluctance motor having reduced radial forces and noise output.

Another aspect of the present technology relates to a switched reluctance motor with a stator having an inductance ratio of less than <NUM>. For example, technology relates to a switched reluctance motor with a stator having an aligned-to-unaligned inductance ratio of less than <NUM>.

One form of the present technology comprises a polyphase switched reluctance motor assembly comprising a stator assembly including a plurality of coils and a stator with a central bore, and a rotor assembly having a plurality of poles. The rotor assembly is arranged within the central bore of the stator assembly and configured to rotate therein and the plurality of coils is configured in a distributed winding configuration.

Furthermore, the stator of the poly-phase switched reluctance motor assembly may include a plurality of projecting stator teeth forming a plurality of stator slots therebetween. Each of the plurality of stator slots may comprise one of the plurality of coils. The total number of stator slots may be determined as a function of a number of phases and a number of rotor poles of the motor. The determination of the total number of stator slots may further include a winding distribution parameter.

In some aspects the plurality of coils may include a coil group for each phase of the poly-phase switched reluctance motor and each of the coils for each coil group are uniformly distributed between the stator slots. Each coil group comprises at least one coil.

In some aspects the poly-phase switched reluctance motor assembly may include at least three motor phases and in use two motor phases are energized at one time during a conduction period. Furthermore one of the two energized phases is provided with a positive direction current and the second of the two energized phases is provided with a negative direction current. Additionally one of the two energized phases may be switched off to a non-energized state and one of the non-energized phases may be switched on to an energized state during each commutation period.

Some aspects of the present technology include a poly-phase switched reluctance motor assembly wherein in use each phase of the motor is energized with the same current value during at least two consecutive conduction periods.

One form of the present technology comprises a polyphase switched reluctance motor assembly including a stator having an outer diameter less than <NUM>.

Another aspect of one form of the present technology is a stator for a poly-phase switched reluctance motor comprising a plurality of stator teeth separated by stator slots and surrounding a central bore and a plurality of coils that are configured in a distributed winding configuration. The plurality of coils may include a coil group for each phase of the poly-phased switched reluctance motor and the coil group may include one or more coils. The central bore of the stator assembly is configured to receive a rotor assembly having a plurality of poles. Furthermore each of the stator slots may comprise one of the plurality of coils.

Another aspect of one form of the present technology is a stator for a poly-phase switched reluctance motor having an inductance ratio of less than <NUM>.

Another aspect of one form of the present technology is a stator for a poly-phase switched reluctance motor having an outer diameter of less than <NUM>.

Another aspect of one form of the present technology is a positive airway pressure device comprising a poly-phase switched reluctance motor including a stator having a distributed winding configuration. The positive airway pressure device configured to provide a supply of pressurized breathable gas.

Another aspect of one form of the present technology is a system for treating a respiratory disorder comprising a therapy device configured to provide a supply of pressurized breathable gas, the therapy device comprising a poly-phase switched reluctance motor including a stator having a distributed winding configuration. The system may further include an air delivery conduit and a patient interface configured to receive the supply of pressurized gas from the therapy device via the air delivery conduit and deliver the supply of pressurized gas to a patient. The system may additionally include a humidifier configured to humidify the supply of pressurized gas.

The invention is a method as defined in claim <NUM>. It is a method of controlling a switched reluctance motor assembly comprising at least three phases. The method comprising during each conduction period energizing a first phase with a negative direction current, energizing a second phase with a positive current and having at least one non-energized phase and during each commutation period switching off one of the first phase or the second phase to a non-energized state and switching on one of the non-energized phases to an energized state with the same direction current as the first or second phase that was switched off. According to the invention, the switched reluctance motor assembly includes a distributed winding configuration.

Embodiments of the switched reluctance motor may be implemented without the use of permanent magnets for rotation of the rotor or such as having no permanent magnets within the stator.

Although described in relation to medical devices the SR motors of the present technology may be used in a range of applications.

In one form, the present technology comprises a switched reluctance motor including a stator having distributed coil windings. In a case of a distributed windings configuration, the coils are placed or wound into the slots. With such a distributed winding, each coil winding may encircle or encompass at least two stator teeth (or more) while skipping over at least one stator slot (or more). The coils may have full pitch or fractional pitch. The number of slots that are occupied with the coils of one phase depend on the number of rotor poles and a winding distribution parameter. The winding distribution parameter indicates how many adjacent slots are occupied with coil segments of the same phase.

In the exemplary stator assemblies as shown in <FIG> and <FIG> the winding distribution parameter is <NUM> as each coil segment (i.e., the coil portion within a stator slot) for each phase is adjacent a coil segment from another phase and not adjacent another coil segment from the same phase. There may be one or more coils for the same phase and coils from the same phase are referred to as a coil group. Each coil group comprises at least one coil, such as one, two, three, four, five or more coils per coil group. Each of the coils in a coil group includes two coil segments (i.e. a pair of coil segments) provided in different stator slots.

<FIG> shows a stator and rotor configuration for a three phase SR motor having <NUM> stator poles (<NUM> stator teeth <NUM> and <NUM> stator slots <NUM>) and <NUM> rotor poles <NUM> according to an example of the present technology. In <FIG>, each phase includes one coil for each phase and the coil is wound with two coil segments within two stator slots <NUM>. The segments are connected by the end turns of the winding which is not shown in the figure. The A phase coil includes A+ and A- coils segments 110a, 110b respectively located within stator slots between stator teeth <NUM> & <NUM> and stator teeth <NUM> & <NUM> respectively. The B phase coil includes B+ and B- coil segments, 112a, 112b respectively that are located within stator slots between stator teeth <NUM> & <NUM> and stator teeth <NUM> & <NUM> respectively. The C phase coil includes C+ and C- coil segments 114a, 114b respectively that are located within stator slots between stator teeth <NUM> & <NUM> and stator teeth <NUM> & <NUM>. Thus, each stator coil is located in a slot between two stator teeth and adjacent winding coils from different phases share an association with stator teeth that separate them. In this configuration, each stator coil segment from the same phase is separated from the other stator coil segment of the same phase by three stator teeth. The coils are not wound around a single stator tooth.

<FIG> and <FIG> illustrate a stator and rotor configuration for a three phase SR motor having <NUM> stator poles (<NUM> stator teeth <NUM> and <NUM> stator slots <NUM>) and <NUM> rotor poles <NUM> according to another example of the present technology. In <FIG> the slots are numbered "<NUM>" through "<NUM>" and each tooth, although not shown with a number, may be considered to have the same number as the numbered slot to the left of the tooth. (i.e., stator tooth <NUM> is between stator slots <NUM> and <NUM>, etc.) In this arrangement there are two coil winding groups for each phase, each group includes one coil formed of two coil segments that occupy two stator slots. The coil segments are distributed evenly around the stator and each coil segment for a single phase is separated by three stator teeth. In <FIG>, stator slots numbered <NUM> and <NUM> and coil 214b are each shown twice simply for purposes of more clearly illustrating the coil windings pattern. For example, phase A coil segments 210a and 210b are separated by stator teeth <NUM>, <NUM> and <NUM> are wound through slots numbered <NUM> and <NUM> to be located in slots <NUM> and <NUM>. In the illustrated example phase A coil segments 210a, 210b, 210c and 210d are located in stator slots <NUM>, <NUM>, <NUM> and <NUM>, between stator teeth <NUM> and <NUM>; <NUM> and <NUM>; <NUM> and <NUM>; and <NUM> and <NUM> respectively. Phase B coil segments 212a, 212b, 212c and 21d are located in slots <NUM>, <NUM>, <NUM> and <NUM>, between stator teeth <NUM> and <NUM>; <NUM> and <NUM>; <NUM> and <NUM>; and <NUM> and <NUM> respectively. Phase C coil segments 214a, 214b, 214c and 214d are located in slots <NUM>, <NUM>, <NUM> and <NUM>, between stator teeth <NUM> and <NUM>, <NUM> and <NUM>; <NUM> and <NUM>; and <NUM> and <NUM> respectively. Thus, each stator slot includes a single coil segment from one coil. A skilled addressee would appreciate that the coils or coil segments for the different phases may be arranged in a different order.

Although <FIG> and <FIG> refer to three phase motors (i.e., phases A B and C), it is to be understood that the motor may comprise a different number of phases such as two, four, five or more phases. The number of stator slots or stator teeth for different SR motor configurations may be determined as a function of the number of phases and the number of rotor poles. The winding distribution parameter may also be used in this determination for example using the following equation: <MAT> Thus, the total number of stator slots may be a multiple of number of phases and number of rotor poles of the motor. Moreover, the total number of stator slots may be a multiple of a winding distribution parameter.

The stator is formed as a lamination stack for example of steel laminations such as silicon steel e.g. M19 grade silicon steel (M19_29G). The rotor may be formed of the same material as the stator or another type of ferromagnetic material like ferrite or iron cobalt alloys. The coils may be formed of any wire gauge preferably in the range of <NUM> to <NUM> gauge wire, for example, each of the coils may be formed from American wire gauge (AWG) <NUM>. The number of turns of the wire is determined by the voltage of the motor. For example the coils may include <NUM>-<NUM> turns per coils such as <NUM> turns per coil. In some cases, each turn of the coil may have one or more wires in hand such as a number in a range of <NUM> to <NUM> wires in hand per turn. For example, it may have six wires in hand per turn. Thus, in one example winding, the wire may be AWG <NUM>, and each coil may have <NUM> turns with <NUM> wires in hand. However, a skilled addressee would understand that the coils may be formed of other material and include a different number of turns per coil and number of wires etc..

A SR motor having a distributed winding configuration distributes the flux between the teeth that each of the phase coils is associated rather than concentrating the flux in a single stator tooth. This results in the radial electromagnetic forces acting between the stator and the rotor being distributed along the stator teeth that are associated with the energized coils. Thus, in the three phase stator arrangement illustrated in <FIG> the electromagnetic force is applied to four teeth with a <NUM>° mechanical phase shift at the same time, see <FIG>. In contrast a conventional three phase concentrated stator as in <FIG> applies the electromagnetic force to two teeth with a <NUM>° phase shift at the same time. Therefore in the exemplary SR motor with distributed windings the peak radial force applied to each tooth is less than in a conventional concentrated winding. In other words, the distribution permits a reduction in radial forces. For example in a SR motor comprising a <NUM>/<NUM> rotor configuration as illustrated in <FIG> the peak radial force in each tooth may be <NUM> Newtons compared to 518N per tooth in a <NUM>/<NUM> concentrated winding conventional SR motor as illustrated in <FIG>. The distribution of the radial electromagnetic forces reduces vibration and consequently reduces noise produced from the SR motor.

The SR motor including a distributed winding configuration of the present technology may have a low aligned to unaligned inductance ratio, such as an inductance ratio of less than <NUM>, or less than <NUM> e.g. between <NUM> and <NUM>.

Advantageously the SR motor including a distributed winding configuration according to the present technology allows for smaller lower power SR motors to be made that produce enough torque to run small high speed devices (up to <NUM>,<NUM> rpm). A small SR motor is understood to mean a SR motor having a stator outer diameter of less than <NUM>, such as <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or less. However, it is to be understood that a SR motor having a distributed winding configuration may also be used in larger motors than have stator outer diameters greater than <NUM>.

The rotor includes at least two rotor poles <NUM>, <NUM>, the rotor poles form rotor teeth that extend out from a central rotor core. In <FIG>, the rotor has two rotor teeth <NUM>-<NUM>, <NUM>-<NUM>. In <FIG>, the rotor has four rotor teeth <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. Each of the rotor teeth may have a width that is wider than the width of a single stator tooth. This can help to distribute the radial electromagnetic forces acting between the stator and the rotor between multiple stator teeth that are associated with the energized coils. In this example of <FIG>, the width of a rotor tooth may be approximately equal to the width of a stator tooth (e.g., the length of the inner arc surface of an end of the stator tooth) plus some width such as a function of a measure of the width of the gap between adjacent stator teeth. The gap <NUM> being the stator slot width at the inner end of the stator slot (the inner end being the end closest to the rotor). According to the invention, the width of a rotor tooth is approximately equal to the width of the stator tooth plus two times the width of the gap between stator teeth. In this regard, the rotor width may be understood to refer to a length along a surface at an end of the rotor tooth that may be formed as an arc at an end of each tooth of the rotor.

In some versions of the present technology, each stator tooth may have tooth tips 213a, 213b (labeled in <FIG>) that form projections on either side of a stator tooth and that extend the width of the stator while still permitting a gap between the stator teeth. The teeth tips can serve to smooth the field in air gap between stator teeth and help to reduce noise. The tips may also help with keeping the winding in the gap or helping to prevent the winding from shifting to the rotor area of the bore. In some versions of the present technology, a suitable stator tooth width may be about <NUM>. However, other widths may be employed, such as a width in a range of <NUM> to <NUM>. That stator tooth width may increase by the width of the tooth tips when included. In some cases, the rotor pole width may be about <NUM>. However, other widths may be employed, such as a width in a range of <NUM> to <NUM>.

The central angles of the stator and rotor poles may be as significant as absolute width values of the teeth. For example, in some typical motor designs, the central angle of the stator and rotor poles may be approximately the same or have a very small difference between them such as a few degrees. However, in some versions of the present technology, the angles may be significantly different, such as having an angle difference of more than several degrees (e.g., more than <NUM> degrees such as in a difference range from <NUM> degrees to <NUM> degrees, or such as in a difference range of <NUM> degrees to <NUM> degrees. For example, the stator central angle, such as the angle formed from the center of the stator with imaginary lines extending radially to the edges of a stator's tooth or stator's tips (see, e.g., angle SA illustrated in <FIG>) may be about <NUM> degrees (e.g., <NUM>°). In such an example, the rotor central angle, such as the angle formed from the center of the rotor with imaginary lines extending radially to the edges of a rotor's tooth (see, e.g., angle RA illustrated in <FIG>) may be about <NUM> degrees (e.g., <NUM> °). Such a difference between the stator central angle and rotor central angle is very significant (e.g., approximately <NUM> degrees).

The rotor may be formed of a suitable material such as silicon steel e.g. M19 grade silicon steel (M19_29G) or another type of ferromagnetic material like ferrite or iron cobalt alloys.

As mentioned previously, torque in SR motors is proportional to the difference in a phase self-inductances in an aligned and non-aligned position when the appropriate phase is energized. It has been determined that using a distributed stator winding configuration in a SR motor of the present technology may produce a significant mutual inductance variation between certain positions of the rotor. This mutual inductance may be utilized to produce a higher torque at small power (less than hundred watts such as <NUM> Watts, <NUM> Watts or <NUM> Watts) SR motor design. <FIG> illustrates an example of the self and mutual inductances produced in a SR motor according to the present technology. The self-inductances Laa, Lbb and Lcc show significantly less variation in the inductance generated at the different rotor positions than the mutual inductances Lab, Lac and Lbc. The mutual inductance variation is approximately eight times the variation range generated by the self-inductances in the example shown. As torque is proportional to the difference of align and non-align values of the inductance in SR motors the mutual inductance may be utilised to produce a larger portion of the torque. The total torque produced in the motor is the sum of the components related to self-inductance and the mutual inductance.

The stator of the SR motor of the present technology includes at least three motor phases. Due to the mutual inductance producing a large portion of the torque, the SR motor of the present technology is, according to the invention, configured to energize two phases at the same time during each conduction period. A first phase is energized with a positive direction current and a second phase is energized with a negative direction current resulting in a net flux increase in the motor and producing a higher torque. Two phases are energised at the same time and follow a specific sequence to cause the rotor to rotate. Each phase of the motor may be energized with the same current value during at least two consecutive conduction periods. One of the two energized phases is switched off to a non-energized state and one of the non-energized phases is switched on to an energized state during each commutation period. The timing of the commutation period or switching is controlled to facilitate smooth rotation of the motor and reduce cogging.

<FIG> shows an exemplary commutation for a SR motor comprising a distributed stator as shown in <FIG>. In a first step phase A may be energised with a positive direction current, phase B may be energised with a negative direction current and phase C may be non-energised (zero current) (i.e., A+B-). This will cause the rotor to move towards the alignment position shown in <FIG>. In the second step, phase A may continue to be energised with a positive direction current, phase B is switched off to an non-energized state (zero current) and phase C is energized with a negative direction current (i.e. A+C-). This will cause the rotor to move towards the alignment positions shown in <FIG>. In the third step, the phase A is switched off to an non-energized state (zero current), phase B is energized with a positive direction current and phase C continues to be energized with a negative direction current (i.e. B+C-). This will cause the rotor to move towards the alignment position shown in <FIG>. This sequential switching of the phases continues such that the fourth step would be B+A- causing the rotor to move towards the alignment position shown in <FIG>. The fifth step, C+A-, causing the rotor to move towards the alignment position shown in <FIG>. The sixth step, C+B-, causing the rotor to move towards the alignment position shown in <FIG>. Then the cycle repeats again by returning to A+B- to provide a full <NUM>° revolution of the rotor. The specific timing of the switching or commutation of the energization of the phases may be varied to adjust the performance of the motor and reduce torque ripple.

<FIG> shows an example of the torque produced for different current sequences relative to the rotor position in a SR motor comprising a stator and rotor configuration as shown in <FIG>. For example for a rotor position between <NUM>° to <NUM>°, the slope of Lac produces the largest proportion of the torque. <MAT> Where Ta the instantaneous torque value, ia,ib and ic are instantaneous values of the current in phases A, B and C respectively. Laa is the total inductance of phase A. Lab is the mutual inductance between phases A and B and Lac is the mutual inductance between phases A and C respectively.

In contrast in a conventional SR motor, where only the self-inductance component is producing the torque, i.e. <MAT>.

A method of controlling a switched reluctance motor comprising at least three phases may include during each conduction period energizing a first phase with a negative direction current, energizing a second phase with a positive current and having at least one non-energized phase and during each commutation period switching off one of the first phase or the second phase to a non-energized state and switching on one of the non-energized phases to an energized state with the same direction current as the first or second phase that was switched off. The switched reluctance motor may include a distributed winding configuration as described above.

In some aspects of the present technology the SR motor may be controlled using a sensorless control. In this arrangement when the rotor passes the non-energized phase, the back EMF, induced in the phase can be detected and filtered in order to remove the noise. The signal is proportional to the rotor angle and may be used to estimate the position of the rotor.

An example of a motor assembly <NUM> that may be implemented with the switched reluctance motor technology described herein is illustrated in <FIG>. As seen in <FIG> and <FIG>, the motor assembly <NUM> may include a motor housing <NUM>, an end bell <NUM> and one or more impeller(s) <NUM>. An example end bell is shown in <FIG>. An example motor housing is illustrated in <FIG>. The motor assembly may also optionally include an encoder <NUM>, such as an optical encoder to detect rotation and/or positioning (e.g., absolute or relative movement) of the shaft of the rotor assembly. As seen in <FIG>, a housing of the encoder may be coupled to the end bell <NUM> with one or more fasteners, such as screws 3132a. Corresponding fastener holes <NUM> on the end bell <NUM> and motor housing <NUM> as seen in <FIG>, <FIG>, <FIG> and <FIG> receive additional fasteners, such as screws 3132b etc., for joining and holding the end bell <NUM> and motor housing <NUM> together. Other types of fasteners may also be implemented such as bolts, snap fit structures, clips, rivets, etc. for joining the structures of the motor assembly. As shown in <FIG>, the motor housing may optionally include a wiring aperture <NUM>. The wiring aperture can permit lead wires of the coils of the stator assembly to pass out of the motor assembly when the stator assembly is installed within the motor assembly.

As seen in more detail in the cross sectional view of <FIG>, the motor housing <NUM> and end bell <NUM> may contain the stator assembly <NUM> and rotor assembly <NUM> (on <FIG>). (the rotor assembly <NUM> is not shown in <FIG>). The stator assembly <NUM> may include a stator <NUM> and coils in any configuration as previously described such as the stator configuration illustrated in <FIG>. As illustrated in <FIG>, the stator <NUM> of such a stator assembly, like the rotor, can be formed in a laminated stack. An example coil configuration is illustrated in <FIG> showing the stator <NUM> with stator teeth <NUM> and stator slots <NUM>. Coil groups for phases A, B and C are shown.

The rotor assembly <NUM> may include a rotor in any configuration as previously described such as the rotor configuration also illustrated in <FIG>. In this regard, the rotor assembly may include a rotor <NUM> and shaft <NUM> as illustrated in <FIG>. As illustrated, the rotor may be a laminated rotor stack (e.g., a plurality of stacked plates) that are bonded to the shaft using a primer and adhesive. The rotor assembly may be mounted for rotation within the motor housing <NUM> and end bell <NUM> with a set of bearings 3160a, 3160b through which the shaft ends are inserted. The bearings 3160a, 3160b may each reside in a cylindrical bearing seat 3161a, 3161b in each of the end bell <NUM> and the motor housing <NUM> respectively. The shaft may also be positioned within the assembly with a spring <NUM>. The impeller(s) <NUM> may be press fit at an impeller end of the shaft <NUM> opposite an encoder end of the shaft <NUM>. Alternatively, the shaft may have impellers at both ends of the shaft (not shown). The rotor assembly may also include one or more balance rings 3164a, 3164b. The motor assembly or the impeller(s) may be inserted or positioned within a volute such as the example volute illustrated in <FIG> so that the motor assembly may serve as part of a blower of a flow generator.

In one form, the present technology comprises apparatus for treating a respiratory disorder. The apparatus may comprise a flow generator or blower including a switched reluctance motor for supplying pressurised respiratory gas, such as air, to the patient <NUM> via an air delivery tube <NUM> leading to a patient interface <NUM>.

In one form, the present technology comprises method for treating a respiratory disorder comprising the step of applying positive pressure to the entrance of the airways of a patient <NUM> using a pressure device including a switched reluctance motor.

In one form, the present technology comprises a method of treating Obstructive Sleep Apnea in a patient by applying nasal continuous positive airway pressure to the patient using a patient interface.

In certain embodiments of the present technology, a supply of air at positive pressure is provided to the nasal passages of the patient via one or both nares.

A patient interface <NUM> is provided as seen in <FIG> to deliver the supply of pressurized air to the patient's airways. A number of different types of patient interfaces including non-invasive and invasive interfaces are available. For example non-invasive masks include a nasal mask, full face mask, nasal prongs and nasal pillows and invasive interfaces include a tracheostomy tube. Non-invasive patient interfaces <NUM> comprise a seal-forming structure to engage with a patient's face in use.

As shown in <FIG> a PAP device <NUM> in accordance with one aspect of the present technology comprises mechanical and pneumatic components <NUM>, electrical components <NUM> and is programmed to execute one or more algorithms <NUM>. The PAP device preferably has an external housing <NUM>, preferably formed in two parts, an upper portion <NUM> of the external housing <NUM>, and a lower portion <NUM> of the external housing <NUM>. In alternative forms, the external housing <NUM> may include one or more panel(s) <NUM>. Preferably the PAP device <NUM> comprises a chassis <NUM> that supports one or more internal components of the PAP device <NUM>. In one form a pneumatic block <NUM> is supported by, or formed as part of the chassis <NUM>. The PAP device <NUM> may optionally include a handle <NUM>.

The pneumatic path of the PAP device <NUM> preferably comprises an inlet air filter <NUM>, an inlet muffler <NUM>, a controllable pressure device <NUM> capable of supplying air at positive pressure (preferably a blower <NUM>) including a motor <NUM>, and an outlet muffler <NUM>. One or more transducers <NUM> such as pressure sensors <NUM>, flow sensors <NUM> and speed sensors <NUM> are included in the pneumatic path.

The preferred pneumatic block <NUM> comprises a portion of the pneumatic path that is located within the external housing <NUM>.

The PAP device <NUM> may include an electrical power supply <NUM>, one or more input devices <NUM>, a central controller <NUM>, a therapy device controller <NUM>, a therapy device <NUM>, one or more protection circuits <NUM>, memory <NUM>, transducers <NUM>, data communication interface <NUM> and one or more output devices <NUM>. Electrical components <NUM> may be mounted on a single Printed Circuit Board Assembly (PCBA) <NUM>. In an alternative form, the PAP device <NUM> may include more than one PCBA <NUM>.

The central controller <NUM> of the PAP device <NUM> is programmed to execute one or more algorithm modules <NUM>, preferably including a pre-processing module <NUM>, a therapy engine module <NUM>, a therapy control module <NUM>, and further preferably a fault condition module <NUM>.

A PAP device in accordance with one form of the present technology may include an air filter <NUM>, or a plurality of air filters <NUM>.

In one form, an inlet air filter <NUM> is located at the beginning of the pneumatic path upstream of a blower <NUM>.

In one form, an outlet air filter <NUM>, for example an antibacterial filter, is located between an outlet of the pneumatic block <NUM> and a patient interface <NUM>.

In one form of the present technology, an inlet muffler <NUM> is located in the pneumatic path upstream of a blower <NUM>.

In one form of the present technology, an outlet muffler <NUM> is located in the pneumatic path between the blower <NUM> and a patient interface <NUM>.

In a preferred form of the present technology, a pressure device <NUM> for producing a flow of air at positive pressure is a controllable blower <NUM>. For example the blower may include a switched reluctance motor <NUM> with one or more impellers housed in a volute. The blower may be preferably capable of delivering a supply of air, for example about <NUM> litres/minute, at a positive pressure in a range from about <NUM> cmH<NUM>O to about <NUM> cmH<NUM>O, or in other forms up to about <NUM> cmH<NUM>O.

The pressure device <NUM> is under the control of the therapy device controller <NUM>.

In one form of the present technology, one or more transducers <NUM> are located upstream of the pressure device <NUM>. The one or more transducers <NUM> are constructed and arranged to measure properties of the air at that point in the pneumatic path.

In one form of the present technology, one or more transducers <NUM> are located downstream of the pressure device <NUM>, and upstream of the air circuit <NUM>. The one or more transducers <NUM> are constructed and arranged to measure properties of the air at that point in the pneumatic path.

In one form of the present technology, one or more transducers <NUM> are located proximate to the patient interface <NUM>.

In one form of the present technology, an anti-spill back valve is located between the humidifier <NUM> and the pneumatic block <NUM>. The anti-spill back valve is constructed and arranged to reduce the risk that water will flow upstream from the humidifier <NUM>, for example to the motor <NUM>.

An air circuit <NUM> in accordance with an aspect of the present technology is constructed and arranged to allow a flow of air or breathable gasses between the pneumatic block <NUM> and the patient interface <NUM>.

In one form of the present technology, supplemental oxygen <NUM> is delivered to a point in the pneumatic path.

In one form of the present technology, supplemental oxygen <NUM> is delivered upstream of the pneumatic block <NUM>.

In one form of the present technology, supplemental oxygen <NUM> is delivered to the air circuit <NUM>.

In one form of the present technology, supplemental oxygen <NUM> is delivered to the patient interface <NUM>.

Power supply <NUM> supplies power to the other components of the basic PAP device <NUM>: the input device <NUM>, the central controller <NUM>, the therapy device <NUM>, and the output device <NUM>.

In one form of the present technology, power supply <NUM> is internal of the external housing <NUM> of the PAP device <NUM>. In another form of the present technology, power supply <NUM> is external of the external housing <NUM> of the PAP device <NUM>.

In one form of the present technology power supply <NUM> provides electrical power to the PAP device <NUM> only. In another form of the present technology, power supply <NUM> provides electrical power to both PAP device <NUM> and humidifier <NUM>.

A PAP device <NUM> may include one or more input devices <NUM>. Input devices <NUM> comprises buttons, switches or dials to allow a person to interact with the PAP device <NUM>. The buttons, switches or dials may be physical devices, or software devices accessible via a touch screen. The buttons, switches or dials may, in one form, be physically connected to the external housing <NUM>, or may, in another form, be in wireless communication with a receiver that is in electrical connection to the central controller <NUM>.

In one form the input device <NUM> may be constructed and arranged to allow a person to select a value and/or a menu option.

In one form of the present technology, the central controller or processor <NUM> is a dedicated electronic circuit configured to receive input signal(s) from the input device <NUM>, and to provide output signal(s) to the output device <NUM> and / or the therapy device controller <NUM>.

In one form, the central controller <NUM> is an application-specific integrated circuit. In another form, the central controller <NUM> comprises discrete electronic components.

In one form of the present technology, the central controller <NUM> is a processor suitable to control a PAP device <NUM> such as an x86 INTEL processor.

A processor <NUM> suitable to control a PAP device <NUM> in accordance with another form of the present technology includes a processor based on ARM Cortex-M processor from ARM Holdings. For example, an STM32 series microcontroller from ST MICROELECTRONICS may be used.

Another processor <NUM> suitable to control a PAP device <NUM> in accordance with a further alternative form of the present technology includes a member selected from the family ARM9-based <NUM>-bit RISC CPUs. For example, an STR9 series microcontroller from ST MICROELECTRONICS may be used.

In certain alternative forms of the present technology, a <NUM>-bit RISC CPU may be used as the processor <NUM> for the PAP device <NUM>. For example a processor from the MSP430 family of microcontrollers, manufactured by TEXAS INSTRUMENTS, may be used.

The processor <NUM> is configured to receive input signal(s) from one or more transducers <NUM>, and one or more input devices <NUM>.

The processor <NUM> is configured to provide output signal(s) to one or more of an output device <NUM>, a therapy device controller <NUM>, a data communication interface <NUM> and humidifier controller <NUM>.

In some forms of the present technology, the processor <NUM>, or multiple such processors, is configured to implement the one or more methodologies described herein such as the one or more algorithms <NUM> expressed as computer programs stored in a non-transitory computer readable storage medium, such as memory <NUM>. In some cases, as previously discussed, such processor(s) may be integrated with a PAP device <NUM>. However, in some forms of the present technology the processor(s) may be implemented discretely from the flow generation components of the PAP device <NUM>, such as for purpose of performing any of the methodologies described herein without directly controlling delivery of a respiratory treatment. For example, such a processor may perform any of the methodologies described herein for purposes of determining control settings for a ventilator or other respiratory related events by analysis of stored data such as from any of the sensors described herein.

Preferably PAP device <NUM> includes a clock <NUM> that is connected to the central controller <NUM>.

In one form of the present technology, the therapy device <NUM> is configured to deliver therapy to a patient <NUM> under the control of the central controller <NUM>. Preferably the therapy device <NUM> is a positive air pressure device <NUM>.

In one form of the present technology, therapy device controller <NUM> is a therapy control module <NUM> such as for pressure control that forms part of the algorithms <NUM> executed by the processor <NUM>.

In one form of the present technology, therapy device controller <NUM> is a dedicated motor control integrated circuit. For example, in one form a MC33035 brushless DC motor controller, manufactured by ONSEMI is used.

Preferably a PAP device <NUM> in accordance with the present technology comprises one or more protection circuits <NUM>.

One form of protection circuit <NUM> in accordance with the present technology is an electrical protection circuit.

One form of protection circuit <NUM> in accordance with the present technology is a temperature or pressure safety circuit.

In accordance with one form of the present technology the PAP device <NUM> includes memory <NUM>, preferably non-volatile memory. In some forms, memory <NUM> may include battery powered static RAM. In some forms, memory <NUM> may include volatile RAM.

Preferably memory <NUM> is located on PCBA <NUM>. Memory <NUM> may be in the form of EEPROM, or NAND flash.

Additionally or alternatively, PAP device <NUM> includes removable form of memory <NUM>, for example a memory card made in accordance with the Secure Digital (SD) standard.

In one form of the present technology, the memory <NUM> acts as a non-transitory computer readable storage medium on which is stored computer program instructions expressing the one or more methodologies described herein, such as the one or more algorithms <NUM>.

Transducers may be internal of the device, or external of the PAP device. External transducers may be located for example on or form part of the air delivery circuit, e.g. the patient interface. External transducers may be in the form of non-contact sensors such as a Doppler radar movement sensor that transmit or transfer data to the PAP device.

A flow transducer <NUM> in accordance with the present technology may be based on a differential pressure transducer, for example, an SDP600 Series differential pressure transducer from SENSIRION. The differential pressure transducer is in fluid communication with the pneumatic circuit, with one of each of the pressure transducers connected to respective first and second points in a flow restricting element. Other flow sensors may also be implemented such as a hot wire flow sensor.

In use, a signal representing total flow Qt from the flow transducer <NUM> is received by the processor <NUM>.

A pressure transducer <NUM> in accordance with the present technology is located in fluid communication with the pneumatic circuit. An example of a suitable pressure transducer is a sensor from the HONEYWELL ASDX series. An alternative suitable pressure transducer is a sensor from the NPA Series from GENERAL ELECTRIC.

In use, a signal from the pressure transducer <NUM>, is received by the processor <NUM>. In one form, the signal from the pressure transducer <NUM> is filtered prior to being received by the processor <NUM>.

In one form of the present technology a motor speed signal <NUM> is generated. A motor speed signal <NUM> is preferably provided by therapy device controller <NUM>. Motor speed may, for example, be generated by a speed sensor, such as a Hall effect sensor.

In one preferred form of the present technology, a data communication interface <NUM> is provided, and is connected to processor <NUM>. Data communication interface <NUM> is preferably connectable to remote external communication network <NUM>. Data communication interface <NUM> is preferably connectable to local external communication network <NUM>. Preferably remote external communication network <NUM> is connectable to remote external device <NUM>. Preferably local external communication network <NUM> is connectable to local external device <NUM>.

In one form, data communication interface <NUM> is part of processor <NUM>. In another form, data communication interface <NUM> is an integrated circuit that is separate from processor <NUM>.

In one form, remote external communication network <NUM> is the Internet. The data communication interface <NUM> may use wired communication (e.g. via Ethernet, or optical fibre) or a wireless protocol to connect to the Internet.

In one form, local external communication network <NUM> utilises one or more communication standards, such as Bluetooth, or a consumer infrared protocol.

In one form, remote external device <NUM> is one or more computers, for example a cluster of networked computers. In one form, remote external device <NUM> may be virtual computers, rather than physical computers. In either case, such remote external device <NUM> may be accessible to an appropriately authorised person such as a clinician.

Preferably local external device <NUM> is a personal computer, mobile phone, tablet or remote control.

An output device <NUM> in accordance with the present technology may take the form of one or more of a visual, audio, and haptic output. A visual output may be a Liquid Crystal Display (LCD) or Light Emitting Diode (LED) display. An audio output may be a speaker or audio tone emitter.

A display driver <NUM> receives as an input the characters, symbols, or images intended for display on the display <NUM>, and converts them to commands that cause the display <NUM> to display those characters, symbols, or images.

A display <NUM> is configured to visually display characters, symbols, or images in response to commands received from the display driver <NUM>. For example, the display <NUM> may be an eight-segment display, in which case the display driver <NUM> converts each character or symbol, such as the figure "<NUM>", to eight logical signals indicating whether the eight respective segments are to be activated to display a particular character or symbol.

An pre-processing module <NUM> in accordance with the present technology receives as an input, raw data from a transducer, for example a flow or pressure transducer, and preferably performs one or more process steps to calculate one or more output values that will be used as an input to another module, for example a therapy engine module <NUM>.

In one form of the present technology, the output values include the interface or mask pressure Pm, the respiratory flow Qr, and the leak flow Ql.

In various forms of the present technology, the pre-processing module <NUM> comprises one or more of the following algorithms: pressure compensation algorithm <NUM>, vent flow calculation algorithm <NUM>, leak flow algorithm <NUM> and respiratory flow algorithm <NUM>.

A pressure compensation algorithm <NUM> may receive as an input a signal indicative of the pressure in the pneumatic path proximal to an outlet of the pneumatic block. The pressure compensation algorithm <NUM> estimates the pressure drop in the air circuit <NUM> and provides as an output an estimated pressure, Pm, in the patient interface <NUM>.

A vent flow calculation algorithm <NUM> may receive as an input an estimated pressure, Pm, in the patient interface <NUM> and estimates a vent flow of air, Qv, from a vent <NUM> in a patient interface <NUM>.

A leak flow algorithm <NUM> may receive as an input a total flow, Qt, and a vent flow Qv, and provides as an output a leak flow Ql by calculating an average of Qt-Qv over a period sufficiently long to include several breathing cycles, e.g. about <NUM> seconds.

A respiratory flow algorithm <NUM> may receive as an input a total flow, Qt, a vent flow, Qv, and a leak flow, Ql, and estimates a respiratory flow of air, Qr, to the patient, by subtracting the vent flow Qv and the leak flow Ql from the total flow Qt.

In one form of the present technology, a therapy engine module <NUM> may receive as inputs one or more of a pressure, Pm, in a patient interface <NUM>, and a respiratory flow of air to a patient, Qr, and provides as an output, one or more therapy parameters, such as a CPAP treatment pressure Pt, a level of pressure support, and a target ventilation.

In various forms of the present technology, the therapy engine module <NUM> comprises one or more of the following algorithms: phase determination <NUM>, waveform determination <NUM>, ventilation determination <NUM>, flow limitation determination <NUM>, Apnea/hypopnea determination <NUM>, Snore determination <NUM>, Patency determination <NUM> and Therapy parameter determination <NUM>.

A phase determination algorithm <NUM> may receive as an input a signal indicative of respiratory flow, Qr, and provides as an output a phase of a breathing cycle of a patient <NUM>. The phase output may be a discrete variable with values of one of inhalation, mid-inspiratory pause, and exhalation. Alternatively the phase output is a continuous variable, for example varying from <NUM> to <NUM>, or <NUM> to 2Pi.

In one form, the phase output is determined to have a discrete value of inhalation when a respiratory flow Qr has a positive value that exceeds a positive threshold. In one form, a phase is determined to have a discrete value of exhalation when a respiratory flow Qr has a negative value that is more negative than a negative threshold.

A waveform determination algorithm <NUM> may receive as an input a value indicative of current patient ventilation, Vent, and provides as an output a waveform of pressure vs. phase. A ventilation determination algorithm <NUM> may receive as an input a respiratory flow Qr, and determines a measure indicative of patient ventilation, Vent. For example the ventilation determination algorithm <NUM> may determine a current value of patient ventilation, Vent, as half the low-pass filtered absolute value of respiratory flow, Qr.

A flow limitation determination algorithm <NUM> may receive as an input a respiratory flow signal Qr and provides as an output a metric of the extent to which the inspiratory portion of the breath exhibits inspiratory flow limitation.

An Apnea/hypopnea determination algorithm <NUM> may receive as an input a respiratory flow signal Qr and provide as an output a flag that indicates that an apnea or an hypopnea has been detected.

An apnea may be said to have been detected when a function of respiratory flow Qr falls below a flow threshold for a predetermined period of time. The function may determine a peak flow, a relatively short-term mean flow, or a flow intermediate of relatively short-term mean and peak flow, for example an RMS flow. The flow threshold may be a relatively long-term measure of flow.

A hypopnea may be said to have been detected when a function of respiratory flow Qr falls below a second flow threshold for a predetermined period of time. The function may determine a peak flow, a relatively short-term mean flow, or a flow intermediate of relatively short-term mean and peak flow, for example an RMS flow. The second flow threshold may be a relatively long-term measure of flow. The second flow threshold is greater than the flow threshold used to detect apneas.

A snore determination algorithm <NUM> may receive as an input a respiratory flow signal Qr and provides as an output a metric of the extent to which snoring is present. Preferably the snore determination algorithm <NUM> comprises the step of determining the intensity of the flow signal in the range of <NUM>-<NUM>. Further preferably, snore determination algorithm <NUM> comprises a step of filtering the respiratory flow signal Qr to reduce background noise, e.g. the sound of airflow in the system from the blower. The snore determination algorithm <NUM> may comprise comparing the noise generated during inspiration to the noise generated during expiration to determine the occurrence of snore, where the noise generated during expiration is considered to relate to the intrinsic device noise.

In one form an airway patency algorithm <NUM> may receive as an input a respiratory flow signal Qr, and determines the power of the signal in the frequency range of about <NUM> and about <NUM>. The presence of a peak in this frequency range is taken to indicate an open airway. The absence of a peak is taken to be an indication of a closed airway.

In one form, the frequency range within which the peak is sought is the frequency of a small forced oscillation in the treatment pressure Pt. In one implementation, the forced oscillation is of frequency <NUM> with amplitude about <NUM> cmH<NUM><NUM>.

In another form, an airway patency algorithm <NUM> may receive as an input a respiratory flow signal Qr, and determines the presence or absence of a cardiogenic signal. The absence of a cardiogenic signal is taken to be an indication of a closed airway.

A therapy parameter determination algorithm <NUM> determines a target treatment pressure Pt to be delivered by the PAP device <NUM>. The therapy parameter determination algorithm <NUM> receives as an input one of more of the following:.

The therapy parameter determination algorithm <NUM> determines the treatment pressure Pt as a function of indices or measures of one or more of flow limitation, apnea, hypopnea, patency, and snore. In one implementation, these measures are determined on a single breath basis, rather than on an aggregation of several previous breaths.

<FIG> is a flow chart illustrating a method <NUM> carried out by the processor <NUM> as one implementation of the algorithm <NUM>. The method <NUM> starts at step <NUM>, at which the processor <NUM> compares the measure of the presence of apnea / hypopnea with a first threshold, and determines whether the measure of the presence of apnea / hypopnea has exceeded the first threshold for a predetermined period of time, indicating an apnea / hypopnea is occurring. If so, the method <NUM> proceeds to step <NUM>; otherwise, the method <NUM> proceeds to step <NUM>. At step <NUM>, the processor <NUM> compares the measure of airway patency with a second threshold. If the measure of airway patency exceeds the second threshold, indicating the airway is patent, the detected apnea / hypopnea is deemed central, and the method <NUM> proceeds to step <NUM>; otherwise, the apnea / hypopnea is deemed obstructive, and the method <NUM> proceeds to step <NUM>.

At step <NUM>, the processor <NUM> compares the measure of flow limitation with a third threshold. If the measure of flow limitation exceeds the third threshold, indicating inspiratory flow is limited, the method <NUM> proceeds to step <NUM>; otherwise, the method <NUM> proceeds to step <NUM>.

At step <NUM>, the processor <NUM> increases the treatment pressure Pt by a predetermined pressure increment ΔP, provided the increased treatment pressure Pt would not exceed an upper limit Pmax. In one implementation, the predetermined pressure increment ΔP and upper limit Pmax are <NUM> cmH<NUM><NUM> and <NUM> cmH<NUM><NUM> respectively. The method <NUM> then returns to step <NUM>.

At step <NUM>, the processor <NUM> decreases the treatment pressure Pt by a decrement, provided the decreased treatment pressure Pt would not fall below a lower limit Pmin, such as a Pmin of <NUM> cmH<NUM><NUM>. The method <NUM> then returns to step <NUM>. In one implementation, the decrement is proportional to the value of Pt-Pmin, so that the decrease in Pt to the lower limit Pmin in the absence of any detected events is exponential. Alternatively, the decrement in Pt could be predetermined, so the decrease in Pt to the lower limit Pmin in the absence of any detected events is linear.

A therapy control module <NUM> in accordance with one aspect of the present technology may receive as an input a target treatment pressure Pt, and controls a therapy device <NUM> to deliver that pressure. The therapy control module <NUM> may receive as an input an EPAP pressure and an IPAP pressure, and controls a therapy device <NUM> to deliver those respective pressures.

In one form of the present technology, a processor executes one or more methods for the detection of fault conditions serving as a fault condition module <NUM>. Preferably the fault conditions detected by the one or more methods includes at least one of the following:.

Upon detection of the fault condition, the corresponding algorithm signals the presence of the fault by one or more of the following:.

As shown in <FIG> and <FIG>, a humidifier <NUM> comprising a water reservoir <NUM> and a heating plate <NUM> may be provided and configured to couple directly or indirectly with a PAP device <NUM>. The water reservoir <NUM> is configured to hold a supply of water <NUM> that is heated by the heater plate <NUM>. The water reservoir <NUM> may hold a given, maximum volume of liquid (e.g. water), typically several hundred millilitres. The water reservoir <NUM> is arranged to receive a flow of breathable gas from the PAP device <NUM> through an air inlet and to add humidity to the breathable gas. The humidified breathable gas exits the humidifier via an outlet for delivery to a patient interface (not shown) via an air delivery conduit <NUM>. The air delivery conduit may include a heated air delivery conduit <NUM>.

One or more transducers or sensors <NUM>, such as a temperature sensor, a relative humidity sensor, an absolute humidity sensor, a flow sensor or other such sensors may be present at one or more locations along the air path to measure the temperature, relative humidity, absolute humidity or flow rate at different locations to assist in controlling the humidifier and an optional heated air delivery conduit <NUM>. For example the heater plate <NUM> may comprise a temperature sensor to measure the temperature of the heating plate. The one or more transducers or sensors <NUM> may also be located external to the air path to measure the ambient conditions such as ambient temperature, ambient relative humidity and/or ambient absolute humidity.

A heated air delivery conduit <NUM> may comprise a heating element <NUM> within or around the heated air delivery conduit <NUM>. For example wires may be positioned between the film and supporting ribs of a heated tube. The heated air delivery conduit <NUM> may also comprise one or more transducers or sensors <NUM> as described above.

Air: In certain forms of the present technology, air supplied to a patient may be atmospheric air, and in other forms of the present technology atmospheric air may be supplemented with oxygen.

Continuous Positive Airway Pressure (CPAP): CPAP treatment will be taken to mean the application of a supply of air or breathable gas to the entrance to the airways at a pressure that is continuously positive with respect to atmosphere, and preferably approximately constant through a respiratory cycle of a patient. In some forms, the pressure at the entrance to the airways will vary by a few centimeters of water within a single respiratory cycle, for example being higher during inhalation and lower during exhalation. In some forms, the pressure at the entrance to the airways will be slightly higher during exhalation, and slightly lower during inhalation. In some forms, the pressure will vary between different respiratory cycles of the patient, for example being increased in response to detection of indications of partial upper airway obstruction, and decreased in the absence of indications of partial upper airway obstruction.

Controller: A device, or portion of a device that adjusts an output based on an input. For example one form of controller has a variable that is under control- the control variable- that constitutes the input to the device. The output of the device is a function of the current value of the control variable, and a set point for the variable. A servo-ventilator may include a controller that has ventilation as an input, a target ventilation as the set point, and level of pressure support as an output. Other forms of input may be one or more of oxygen saturation (SaO<NUM>), partial pressure of carbon dioxide (PCO<NUM>), movement, a signal from a photoplethysmogram, and peak flow. The set point of the controller may be one or more of fixed, variable or learned. For example, the set point in a ventilator may be a long term average of the measured ventilation of a patient. Another ventilator may have a ventilation set point that changes with time. A pressure controller may be configured to control a blower or pump to deliver air at a particular pressure.

Therapy: Therapy in the present context may be one or more of positive pressure therapy, oxygen therapy, carbon dioxide therapy, control of dead space, and the administration of a drug.

Transducers: A device for converting one form of energy or signal into another. A transducer may be a sensor or detector for converting mechanical energy (such as movement) into an electrical signal. Examples of transducers include pressure sensors, flow sensors, carbon dioxide (CO<NUM>) sensors, oxygen (O<NUM>) sensors, effort sensors, movement sensors, noise sensors, a plethysmograph, and cameras.

Volute: The casing of the centrifugal pump that receives the air being pumped by the impeller, slowing down the flow rate of air and increasing the pressure. The cross-section of the volute increases in area towards the discharge port.

Apnea: Preferably, apnea will be said to have occurred when flow falls below a predetermined threshold for a duration, e.g. <NUM> seconds. An obstructive apnea will be said to have occurred when, despite patient effort, some obstruction of the airway does not allow air to flow. A central apnea will be said to have occurred when an apnea is detected that is due to a reduction in breathing effort, or the absence of breathing effort.

Breathing rate: The rate of spontaneous respiration of a patient, usually measured in breaths per minute.

Effort (breathing): Preferably breathing effort will be said to be the work done by a spontaneously breathing person attempting to breathe.

Expiratory portion of a breathing cycle: The period from the start of expiratory flow to the start of inspiratory flow.

Flow limitation: Preferably, flow limitation will be taken to be the state of affairs in a patient's respiration where an increase in effort by the patient does not give rise to a corresponding increase in flow. Where flow limitation occurs during an inspiratory portion of the breathing cycle it may be described as inspiratory flow limitation. Where flow limitation occurs during an expiratory portion of the breathing cycle it may be described as expiratory flow limitation.

Hypopnea: Preferably, a hypopnea will be taken to be a reduction in flow, but not a cessation of flow. In one form, a hypopnea may be said to have occurred when there is a reduction in flow below a threshold for a duration. In one form in adults, the following either of the following may be regarded as being hypopneas:.

Patency (airway): The degree of the airway being open, or the extent to which the airway is open. A patent airway is open. Airway patency may be quantified, for example with a value of one (<NUM>) being patent, and a value of zero (<NUM>), being closed.

Positive End-Expiratory Pressure (PEEP): The pressure above atmosphere in the lungs that exists at the end of expiration.

Peak flow (Qpeak): The maximum value of flow during the inspiratory portion of the respiratory flow waveform.

Respiratory flow, airflow, patient airflow, respiratory airflow (Qr): These synonymous terms may be understood to refer to the PAP device's estimate of respiratory airflow, as opposed to "true respiratory flow" or "true respiratory airflow", which is the actual respiratory flow experienced by the patient, usually expressed in litres per minute.

Upper airway obstruction (UAO): includes both partial and total upper airway obstruction. This may be associated with a state of flow limitation, in which the level of flow increases only slightly or may even decrease as the pressure difference across the upper airway increases (Starling resistor behaviour).

Ventilation (Vent): A measure of the total amount of gas being exchanged by the patient's respiratory system, including both inspiratory and expiratory flow, per unit time. When expressed as a volume per minute, this quantity is often referred to as "minute ventilation". Minute ventilation is sometimes given simply as a volume, understood to be the volume per minute.

Flow rate: The instantaneous volume (or mass) of air delivered per unit time. While flow rate and ventilation have the same dimensions of volume or mass per unit time, flow rate is measured over a much shorter period of time. Flow may be nominally positive for the inspiratory portion of a breathing cycle of a patient, and hence negative for the expiratory portion of the breathing cycle of a patient. In some cases, a reference to flow rate will be a reference to a scalar quantity, namely a quantity having magnitude only. In other cases, a reference to flow rate will be a reference to a vector quantity, namely a quantity having both magnitude and direction. Flow will be given the symbol Q. Total flow, Qt, is the flow of air leaving the PAP device. Vent flow, Qv, is the flow of air leaving a vent to allow washout of exhaled gases. Leak flow, Ql, is the flow rate of unintentional leak from a patient interface system. Respiratory flow, Qr, is the flow of air that is received into the patient's respiratory system.

Leak: Preferably, the word leak will be taken to be a flow of air to the ambient. Leak may be intentional, for example to allow for the washout of exhaled CO<NUM>. Leak may be unintentional, for example, as the result of an incomplete seal between a mask and a patient's face.

Pressure: Force per unit area. Pressure may be measured in a range of units, including cmH<NUM>O, g-f/cm<NUM>, hectopascal. 1cmH<NUM>O is equal to <NUM>-f/cm<NUM> and is approximately <NUM> hectopascal. In this specification, unless otherwise stated, pressure is given in units of cmH<NUM>O. For nasal CPAP treatment of OSA, a reference to treatment pressure is a reference to a pressure in the range of about <NUM>-<NUM> cmH<NUM>O, or about <NUM>-<NUM> cmH<NUM>O. The pressure in the patient interface is given the symbol Pm.

Sound Power: The energy per unit time carried by a sound wave. The sound power is proportional to the square of sound pressure multiplied by the area of the wavefront. Sound power is usually given in decibels SWL, that is, decibels relative to a reference power, normally taken as <NUM>-<NUM> watt.

Sound Pressure: The local deviation from ambient pressure at a given time instant as a result of a sound wave travelling through a medium. Sound power is usually given in decibels SPL, that is, decibels relative to a reference power, normally taken as <NUM> × <NUM>-<NUM> pascal (Pa), considered the threshold of human hearing.

When a particular material is identified as being preferably used to construct a component, obvious alternative materials with similar properties may be used as a substitute.

The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present technology is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates, which may need to be independently confirmed.

Moreover, in interpreting the disclosure, all terms should be interpreted in the broadest reasonable manner consistent with the context. In particular, the terms "comprises" and "comprising" should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced.

Claim 1:
A method of controlling a poly-phase switched reluctance motor assembly, the poly-phase switched reluctance motor assembly including a plurality of stator teeth and a plurality of rotor poles forming rotor teeth that extend out from a central rotor core, wherein a width of a rotor tooth is approximately equal to a width of a stator tooth plus two times a width of a gap between two stator teeth of the plurality of stator teeth, the poly-phase switched reluctance motor assembly also including a distributed winding configuration comprising at least three phases, the method comprising:
during each conduction period energizing a first phase with a negative direction current, energizing a second phase with a positive direction current and having at least one non-energized phase; and
during each commutation period switching off one of the first phase or the second phase to a non-energized state and switching on one of the non-energized phases to an energized state with a same direction current as the first or second phase that was switched off.