Patent Description:
Electric machines with multiple rotors are known and may provide enhanced power over conventional electric machines. However, known multiple-rotor electric machines may provide unsteady output torque characteristics on individual rotors, and may require complex configurations. Moreover, multiple-rotor electric machines may have low durability due to variability in torque at the rotor level during operation. Improvement is desirable.

A prior art electric machine system having the features of the preamble of claim <NUM> is disclosed in <CIT>. Other prior art electric machine systems are disclosed in <CIT>, <CIT> and <CIT>.

In one aspect, the present invention provides an electric machine system as set forth in claim <NUM>.

The electric machine system may comprise: a third electric machine having a plurality of third rotors driven using electric power having a third phase, the third phase different from the first phase and from the second phase, wherein each shaft connects one of the third rotors with the one of the second rotors and the one of the first rotors.

Each of the shafts may be drivingly coupled to the load by one or more gears.

The first rotors may be indexed to have a positional phase offset relative to each other.

The first phase and the second phase may be offset by <NUM> degrees.

The second electric machine may be axially offset from the first electric machine.

The one or more second windings may be circumferentially offset from the one or more first windings.

The shafts may be drivingly coupled to the load via respective gears.

The shafts may have parallel rotation axes.

The first rotors may be disposed to define a first circular array arrangement. The second rotors may be disposed to define a second circular array arrangement. The first circular array arrangement of first rotors may be coaxial with the second circular array arrangement of second rotors. The first circular array arrangement of first rotors may be axially offset from the second circular array arrangement of second rotors.

Embodiments can include combinations of the above features.

Other features will become apparent from the drawings in conjunction with the following description.

In the figures which illustrate example embodiments,.

The disclosure provides electric machines, and in particular improved multiple-rotor electric machines such as motors and generators. In some embodiments, the machines described herein can provide improved operational characteristics and durability. In various aspects, for example, the disclosure provides electric motors and generators having a plurality of magnetized rotors, which may include or be in the form of single bi-pole magnets (i.e., two-pole rotors). The rotors are configured to drive and/or be driven by a common shaft, for example by suitable combinations and configurations of gears.

In some embodiments, the rotors are magnetically indexed, in pairs, with respect to each other and to corresponding electrical windings such that, when a current is passed through the one or more windings, the rotors provide phased rotary power to the common shaft. Alternatively, when torque is applied to the common shaft or gears connected thereto, a phased electrical output may be provided to the windings.

In some embodiments, the rotors are magnetically indexed along different planes perpendicular to the axial direction of the common shaft, and connected by common rotor shafts. That is, all of the rotors in a first plane may share a common phase, and all of the rotors in a second plane may share a common phase which is offset from the phase of the first plane. In some embodiments, there may be <NUM> planes each offset by <NUM> degrees. Any suitable number of planes may be used with suitable offsets.

Various aspects of preferred embodiments of electric machines according to the disclosure are described herein with reference to the drawings.

Electric machines may have more than one rotor. An example of a multi-rotor electric machine is provided in <CIT>.

<FIG> is a schematic perspective view of portions of an embodiment of an electric machine <NUM> having multiple rotors (also referred to herein as a "multi-rotor electric machine"). As illustrated, machine <NUM> comprises magnetic rotors <NUM>, windings <NUM>, stators <NUM>, and shaft <NUM>. In the embodiment shown, machine <NUM> comprises a plurality of magnetic rotors <NUM>, each configured to rotate about an independent rotor shaft <NUM>. Each rotor shaft <NUM> is configured to, under the impetus of magnetic rotors <NUM>, drive shaft <NUM> via gears <NUM> and central gear <NUM> when machine <NUM> is operated as a motor and an electric current is applied to windings <NUM>. Alternatively, magnetic rotors <NUM> are configured to rotate, and thus cause the flow of electric current in windings <NUM>, when a torque is applied to shaft <NUM>, such that machine <NUM> acts as a generator. It should be appreciated that gears <NUM> are shown without teeth in <FIG> and <FIG> for the sake of clarity. Gears <NUM> may be provided in any suitable form, including, for example, toothless wheels engaged by friction.

In the embodiment shown, each rotor shaft is supported by front and back plates with suitable bearings (not shown), and is formed integral with or otherwise connected to a drive gear <NUM>, which is configured to engage a central gear <NUM>. In some embodiments, central gear <NUM> is formed integral with or otherwise connected to shaft <NUM>, such that rotation of one or more rotors <NUM> causes drive gears <NUM> to drive central gear <NUM>, and therefore shaft <NUM>, into rotation.

In some embodiments, rotors <NUM> are configured to operate in electromagnetically independent pairs. That is, rotors 102a, 102b can be grouped magnetically into independent pairs <NUM>, such that there is no provision of magnetic material linking any two pairs 160a, 160b of rotors together, and the links between separate rotor pairs <NUM> are the gears <NUM> or other mechanical couplings between them, and possibly a shared electric phase. The rotors 102a, 102b in a given pair <NUM> can benefit from the provision of common magnetic circuit components, such as stators <NUM> and/or windings <NUM>. Such a configuration can reduce the amount of magnetic material required for operation of the rotors, with corresponding cost and weight savings.

In the embodiment shown in <FIG>, each rotor <NUM> comprises one or more magnets mounted on a rotor shaft <NUM> and retained, particularly when rotating, by containment sheath <NUM>. Magnets <NUM> comprise north and south poles (denoted "N" and "S" respectively in the figures). In some embodiments, rotors <NUM> are bi-pole rotors. In some embodiments, rotors 102a, 102b in a given pair are indexed such that magnets <NUM> are mounted, and rotate, (a) as individual rotors <NUM>, in a desired phase with respect to their pair mates 102a, 102b, and (b) by pairs <NUM>, in a desired paired phase with respect to other pairs <NUM> and winding(s) <NUM>. Advantages associated with this configuration are explained in <CIT>.

Windings <NUM> may be provided in any configuration suitable for use in accomplishing the purposes described herein. For example, single Litz wire or multiple strand windings <NUM> may be used in configuring either machine <NUM>, individual rotors <NUM>, rotors pairs <NUM>, or other desired sets of rotors <NUM>. The use of multiple windings <NUM> in a machine <NUM> can be used, as for example in conjunction with suitable mechanical indexing of the rotors <NUM> to fully or partially provide desired phasings in torque applied by rotors <NUM> to shaft or load <NUM>. For example, <NUM>-phase windings used in known electric machines may be formed by appropriate interconnections of the separate windings in machines <NUM> according to the present disclosure.

As depicted, each rotor-driven gear <NUM> engages the periphery of central gear <NUM> such that total torque applied to central gear <NUM> is the sum of the torques applied by the gears <NUM>. If winding(s) <NUM> are configured substantially circumferentially about axis <NUM> of shaft <NUM> and therefore machine <NUM>, an index angle <NUM> may be defined between equators (that is, the line dividing magnet <NUM> into north and south halves) <NUM> of individual magnets <NUM> and radii <NUM> extending from axis <NUM> to the corresponding rotor <NUM>. By suitable arrangement of rotors <NUM> and/or gears <NUM>, index angles <NUM> may be set at desired values for individual rotors, and sets thereof, with the result that phased torque output applied by each of the rotor pairs <NUM> can be applied to provide smooth, continuous torque to shaft <NUM>, when operated as a motor. When operated as a generator, smooth and continuous current may be output from overall winding(s) <NUM>.

<FIG> depicts an embodiment having <NUM> rotors <NUM> (or <NUM> pairs <NUM>) and <NUM> phases. As will be understood, embodiments described herein can be adapted to <NUM>-rotor, <NUM>-phase systems, <NUM>-rotor, <NUM>-phase systems, and other combinations.

In some embodiments, each rotor 102a in a given pair 160a may be phased magnetically at <NUM> degrees with respect to its pair mate 102b. Further, each of the <NUM> pairs 160a, 160b, 160c, 160d, 160e, 160f may be phased at <NUM> degrees relative to adjacent pairs. It should be appreciated that in <FIG>, for simplicity, reference numerals 160a-f refer only to respective pairs of rotors 102a, 102b.

Likewise, in a <NUM>-rotor, <NUM>-phase system, each adjacent rotor pair 160a, 160b, 160c can be indexed by <NUM> degrees with respect to adjacent pairs. The same logic may be applied to configurations with more or fewer rotors.

However, in spite of providing smooth and continuous torque to central gear <NUM> as an overall system, each gear <NUM> in machine <NUM> suffers from a relatively high torque ripple (i.e., torques variations of a higher amplitude) during operation. That is, owing the nature of the operation of AC machines, the torque delivered by each rotor <NUM> varies from <NUM> to the maximum output torque twice per cycle. The impact of this torque ripple may be substantial in terms of the working life for a gear, as the gears are subjected to a wide variation of stress. The machine <NUM> may require low-backlash gears and/or high strength gears, which are expensive and may nevertheless be subjected to fretting damage over the course of operation.

<FIG> is a simplified schematic perspective view of portions of an example embodiment of an electric machine system <NUM> having multiple rotors on a common shaft. As depicted, machine system <NUM> includes a plurality of multi-rotor machines <NUM>, <NUM>', <NUM>" located in different planes along the axial direction of shaft <NUM>. In some embodiments, as with machine <NUM>, the rotors depicted in <FIG> are magnetically indexed in pairs <NUM> of rotors 102a, 102b which share a common stator <NUM>. In some embodiments, rotors 102a and 102b may be offset by <NUM> degrees. As depicted, in each machine in system <NUM>, each rotor pair 160a, 160b, 160c, 160d, 160e, 160f may have a phase offset of <NUM> degrees relative to adjacent rotor pairs of the same machine. As depicted, the rotors <NUM> of machine <NUM> are disposed to define a circular array arrangement about axis <NUM>, and the rotors <NUM>' of machine <NUM>' are disposed to define a circular array arrangement about axis <NUM> which is axially offset from the circular array arrangement of machine <NUM>. In some embodiments, the circular array arrangement of machine <NUM> may be coaxial with the circular array arrangement of machine <NUM>'.

In an example embodiment using <NUM>-phase power, in first machine <NUM>, windings for rotor pairs 160a, 160d may be supplied with current from a first phase (denoted as phase C). Windings for rotor pairs 160b, 160e may be supplied with current from a second phase (denoted as phase A). Windings for rotor pairs 160c, 160f may be supplied with current from a third phase (denoted as phase B).

In the example embodiment of <FIG>, windings for each pair 160a', 160b', 160c', 160d', 160e', 160f' of rotors 102a', 102b' in second machine <NUM>' are similarly supplied by one of <NUM> phases (phase A, phase B, or phase C). Relative to axis <NUM>, the current for the windings in second machine <NUM>' are phase shifted by <NUM> degrees. As such, windings for pairs 160a' and 160d' are supplied by phase A, windings for pairs 160b' and 160e' are supplied by phase B, and windings for pairs 160c' and 160f' are supplied by phase C.

Similarly, the current for the windings in third machine <NUM>" is phase shifted by <NUM> degrees relative to first machine <NUM>. As such, windings for pairs 160a", 160d" are supplied by B, windings for pairs 160b", 160e" are supplied by phase C, and windings for pairs 160c", 160f" are supplied by phase A.

As depicted, machine <NUM> includes one or more extended rotor shafts 416a which interconnect a given rotor 102a in first machine <NUM> to a corresponding rotor 102a' in second machine <NUM>' and a corresponding rotor 102a" in third machine <NUM>". In some embodiments, shaft 416a interconnects a first rotor 102a and a second rotor 102a' without interconnecting a third rotor 102a". As depicted, the rotors 102a, 102a', 102a" are disposed at different axial positions relative to axis <NUM> of shaft <NUM>. In some embodiments, rotors 102a, 102a', 102a" are coaxial.

The total net torque delivered by rotor shaft 416a may be the sum of the torque provided by rotors 102a, 102a', 102a". Moreover, it will be appreciated that each of rotors 102a, 102a', 102a" is coupled to one of phase A, phase B, and phase C, respectively. As such, the resulting net torque provided to shaft 416a would be the sum of torques provided by rotors which are coupled to phases A, B and C, which are each offset by <NUM> degrees relative to the other phases. As such, the ripple in torque delivered by rotor shaft 416a may be substantially reduced. <FIG> is a diagram depicting the torque delivered by a rotor shaft <NUM> of machine <NUM>. <FIG> is a diagram depicting the torque delivered by rotor shaft 416a of machine system <NUM>. As will be appreciated, the torque delivered by rotor shaft 416a exhibits substantially less torque ripple (i.e., torques variations of a lower amplitude) than machine <NUM>.

Rotor shaft 416b rotatably connects rotor 102b in first machine <NUM> to rotor 102b' in second machine <NUM>' and to rotor 102b" in third machine <NUM>" to define collective rotor 450b. Again, rotor shaft 416b is provided with torque from <NUM> rotors which are coupled to three separate phases A, B and C. As such, the torque delivered by collective rotor 450b exhibits substantially less torque ripple than machine <NUM>. In some embodiments, rotors 102a, 102b in machine <NUM> are mechanically <NUM> degrees out of phase, rotors 102a', 102b' in machine <NUM>' are mechanically <NUM> degrees out of phase, and rotors 102a", 102b" in machine <NUM>" are mechanically <NUM> degrees out of phase with one another. This may further enhance the efficiency of machine system <NUM>.

It should be appreciated that for simplicity, only two extended rotor shafts 416a, 416b are illustrated in <FIG>. In some embodiments there may be a corresponding extended rotor shaft <NUM> for each rotor in first machine <NUM>, provided there is a corresponding rotor in at least a second machine <NUM>' to which the extended rotor shaft <NUM> can be connected. In some embodiments, the number of extended rotor shafts <NUM> may be less than the number of rotors in a given plane. In some embodiments, the extended rotor shafts <NUM> may have parallel rotational axes.

Although <FIG> depicts an electric machine system <NUM> with <NUM> parallel machines <NUM>, <NUM>', <NUM>", it will be appreciated that embodiments with more than <NUM> or fewer than <NUM> parallel machines <NUM> are also contemplated. Similar configurations can be implemented using the appropriate phase differences between magnetic cores in different planes. In embodiments with two machines <NUM>, <NUM>', the first rotor 102a, second rotor 102a' and shaft 416a are coupled for common rotation.

In some embodiments, each rotor shaft <NUM> has a gear <NUM> affixed or connected thereto. As depicted, gear <NUM> is affixed or otherwise attached to rotor shaft <NUM> such that rotation of rotor shaft <NUM> causes gear <NUM> to rotate along the same rotational axis as the rotor shaft <NUM>. Gear <NUM> is configured to engage with central gear <NUM> to drive a load. Given that the torque ripple is substantially reduced for each gear <NUM> owing to the rotor shaft <NUM> shared across machines <NUM>, <NUM>', <NUM>", it will be appreciated that some embodiments disclosed herein may reduce the amplitude of the cyclic stress experienced by gears <NUM> while engaging with central gear <NUM>. This may in turn increase the working life of gears, and may allow for the use of less expensive materials for gears <NUM>. The reduction in the likelihood that gears <NUM> will suffer damage during operation may further increase the reliability and dependability of machine <NUM> relative to known electric machines.

<FIG> is a simplified front cut-away view of the machine <NUM> depicted in <FIG>. As depicted, a common stator <NUM> is provided for each pair <NUM> of rotors 102a, 102b. Each stator <NUM> has a winding <NUM>, although it will be appreciated that in some embodiments, a stator has more than one winding <NUM>. In addition, windings for pairs 160a and 160d receive current from phase A, windings for pairs 160b and 160e receive current from phase B, and windings for pairs 160c and 160f receive current from phase C. It should be appreciated that any two stators can be connected by a single phase. In some embodiments, phase B is offset by <NUM> degrees from phase A, and phase C is offset by <NUM> degrees from phase A. The machine <NUM> may suffer from considerable losses during operation, and uses substantial quantities of iron, which implies greater weight and cost. Moreover, the configuration depicted in <FIG> may require a number of rotors which is divisible by <NUM>. Since the rotors 102a, 102b are provided in pairs, this may limit the possible configurations to those which include <NUM> rotors, <NUM> rotors, <NUM> rotors, or the like.

It may be desirable to have greater flexibility in the number of rotors which can be included in a multi-rotor electric machine. Moreover, it may be desirable to reduce the quantity of iron required for stators and therefore the weight, cost, and losses associated with machine <NUM>.

<FIG> is a simplified front cut-away view of an electric machine system <NUM>. As depicted, machine <NUM> includes a first multi-rotor machine <NUM> located in a first plane. Machine <NUM> includes one stator <NUM> and a plurality of windings <NUM> (depicted as winding 808ab for the winding appearing between rotors 802a and 802b, and so forth) and rotors 802a, 802b, 802c, 802d,. It should be appreciated that machine <NUM> can have any number of rotors <NUM>. That is, the number of rotors <NUM> need not be in multiples of <NUM>, and the rotors need not be indexed in magnetically independent pairs as with machine <NUM>, so there need not be an even number of rotors <NUM>. In some embodiments, there is one common stator <NUM> for all rotors 802a, 802b, 802c, 802d,. , 802n in machine <NUM>, and the electric power is supplied by a single phase (e.g. phase A). In some embodiments, the electric power is supplied in the form of AC electric power and the machine <NUM> operates as an asynchronous machine. In some embodiments, the electric power may be supplied as DC current, and machine <NUM> may operate as a DC motor.

In some embodiments, rotors 802a, 802b, 802c, 802d,. , 802n are disposed in a circular array arrangement circumferentially around axis <NUM> of central shaft <NUM>. An index angle may be defined between equators (i.e. the line dividing north and south poles) for individual magnets for each rotor <NUM> and radii <NUM> extending from axis <NUM> to the corresponding rotor <NUM>. For simplicity, only radii 904c, 904d are depicted for corresponding rotors 802c, 802d and index angles for other rotors <NUM> are omitted. As depicted, rotors 802c and 802d have index angles of <NUM> degrees, because the equator is parallel to radii 904c, 904d, respectively. By suitable positional phase offset of rotors <NUM> and/or rotor gears <NUM>, index angles may be set at desired values for individual rotors, with the result that torque output applied by each rotor <NUM> can be enhanced.

The configuration of machine <NUM> in <FIG> may substantially reduce the amount of iron (e.g. for laminations) required, which may in turn reduce the weight, associated costs, and losses inside machine <NUM> during operation. In some embodiments, the configuration depicted in <FIG> may require <NUM>% less iron to produce similar output power relative to machine <NUM>. It will be appreciated that during operation, the output torque of each rotor <NUM> in machine <NUM> may exhibit a large degree of torque ripple, as each rotor 802a, 802b,. 802n varies between delivering no torque and the maximum output torque.

<FIG> is a side view of electric machine system <NUM> illustrating multiple machines <NUM>, <NUM>', <NUM>" in parallel on different planes. As depicted, machine <NUM> includes first machine <NUM> in a first plane, second machine <NUM>' in a second plane, and third machine <NUM>" in a third plane. The machines <NUM>, <NUM>', <NUM>" are positioned substantially perpendicularly to axis <NUM> of shaft <NUM>. In some embodiments, machines <NUM>, <NUM>', <NUM>" are substantially parallel to one another. In some embodiments, the circular array arrangement of rotors of machine <NUM> may be coaxial with the circular array arrangement of rotors of machine <NUM>'. In some embodiments, the circular array arrangement of rotors of machine <NUM> may be axially offset from the second array arrangement of rotors of machine <NUM>'.

Rotor shafts <NUM> (e.g. rotor shaft 816d) interconnect a respective rotor in machine <NUM> (e.g. rotor 802d) to a respective rotor in machine <NUM>' (e.g. rotor 802d') and to a respective rotor in machine <NUM>" (e.g. rotor 802d"). As depicted, respective gears <NUM> are connected or affixed to rotor shafts <NUM>. As depicted, gear <NUM> is affixed or otherwise attached to rotor shaft <NUM> in a manner such that rotation of rotor shaft <NUM> causes gear <NUM> to rotate in the same direction and with a common rotational axis to shaft <NUM>. In some embodiments, rotor shaft 816d is drivingly coupled to shaft <NUM> or a load via gear 818d. As referenced herein, the expression "drivingly coupled" encompasses an arrangement in which the rotation of one element results in the rotation or movement of another element (e.g., directly or indirectly). For example, although rotor shaft 816d does not directly touch shaft <NUM>, the rotation of rotor shaft 816d causes gear 818d to rotate, which engages the central gear <NUM> and causes shaft <NUM> to rotate. For simplicity, <FIG> depicts gear 818c coupled to rotor shaft 816c and gear 818d coupled to rotor shaft 816d. Reference numerals for other gears and rotor shafts have been omitted for simplicity. As depicted, rotors shafts 816c, 816d may have parallel rotational axes. In some embodiments, an additional gear 818c' may be connected to rotor shaft 816c. The use of additional gear 818c' may further reduce the stress and strain experienced by gears during operation, as the stress and strain is distributed between two gears 818c, 818c' rather than concentrated on a single gear. Example embodiments which incorporate more than one gear are described in further detail below with reference to <FIG>.

The windings <NUM> of first machine <NUM> are supplied with electric power from a first single phase (phase A). The windings <NUM>' of second machine <NUM>' are supplied with electric power from a second single phase (phase B). In some embodiments, the windings <NUM>" of third machine <NUM>" may be supplied with electric power from a third single phase (phase C). Phase B may be offset from phase A by <NUM> degrees. Phase C may be offset from phase A by <NUM> degrees. As noted above, each machine <NUM>, <NUM>', <NUM>" includes a single common stator <NUM>, <NUM>', <NUM>", respectively, and as such each machine <NUM>, <NUM>', <NUM>" is powered by a unique phase.

The output torque from each rotor shaft (e.g. 816d) is equal to the sum of torques output by individual rotors (e.g. 802d, 802d', 802d"). If phase B is offset from phase A by <NUM> degrees, and phase C is offset from phase A by <NUM> degrees, the net output torque provided by rotor shaft 816d may have substantially less torque ripple relative to the output torque of any individual machine <NUM>, <NUM>' or <NUM>". The output torque waveform may be similar in nature to that of <FIG> (although the quantitative torque output might not be similar between machines <NUM> and <NUM>). For example, if the output torque of rotor 802d varies between <NUM> and the maximum output torque, then the sum of the output torque of rotor 802d with rotors 802d' and 802d" (which are offset by <NUM> degrees) would result in a far more stable output torque with less torque ripple than a single rotor.

Machine system <NUM> may also provide additional versatility and flexibility relative to other electric machines. For example, the same magnetic circuit can be used for both high-input speed generators, as well as low output speed propulsion motors by selecting the appropriate ratio between the gears <NUM> and the central gear <NUM>. The speed selection may be carried out without the addition of a separate gearbox, which avoids the costs and weight associated with a gearbox as would be required by other electric machines.

Moreover, the machine <NUM> may allow for the use of the same bi-pole rotors <NUM> in machines of different sizes, because any suitable number of rotors <NUM> can be used to obtain the desired output torque. As such, cost savings may be achieved by using the same standardized rotors <NUM> across different applications, rather than having to tailor rotors <NUM> depending on the specific intended use of the machine <NUM>. In addition, in machine <NUM>, winding coils are exposed and the magnetic rotors <NUM> are distributed around the machine assembly, which may facilitate heat extraction from the machine <NUM> in a more convenient manner relative to machines where copper windings are contained within the stator iron. This may help to increase the power per weight and power per volume ratios of machine <NUM> relative to other electric machines.

<FIG> is a simplified schematic side cross-sectional view of an individual rotor shaft 816d of machine <NUM>. As depicted, each rotor shaft <NUM> interconnects rotors 802d, 802d', 802d" to gears 818d, 818d'. <FIG> is a view of rotor 802d on axis A-A in <FIG>. As depicted, rotor 802d includes a magnet with north and south poles and an equator. <FIG> is a view of rotor 802d' on axis B-B in <FIG>. As depicted, rotor 802d' includes a magnet with north and south poles, and is mechanically indexed by <NUM> degrees relative to rotor 802d. <FIG> is a view of rotor 802d" on axis C-C in <FIG>. As depicted, rotor 802d" includes a magnet with north and south poles, and is mechanically indexed by <NUM> degrees relative to rotor 802d, and by <NUM> degrees relative to rotor 802d'. It should be appreciated that although <FIG> illustrate a particular configuration of rotor indexing in machine <NUM>, it is contemplated that other configurations may be used in order to enhance the operational characteristics of machine system <NUM>.

In some embodiments, each rotor <NUM> in first machine <NUM> is connected to a respective rotor <NUM>' in second machine <NUM>' and a respective rotor <NUM>" in third machine <NUM>" via a rotor shaft <NUM>. In some embodiments, there may be fewer rotor shafts <NUM> than there are rotors in machine <NUM>.

<FIG> depicts an alternative configuration of an electric machine system <NUM>. Machine system <NUM> is similar to machine system <NUM> in that each machine <NUM>, <NUM>', <NUM>" contains a plurality of rotors and a single stator and phase for each machine. Machine system <NUM> differs in that one winding <NUM> is provided between every pair of rotors. For example, referring to <FIG>, winding 808ab may be provided between rotors 802a and 802b, and winding 808cd may be provided between rotors 802c and 802d. However, every second winding (e.g. windings 808bc, 808de, 808fg, 808hi, 808jk, 808lm) is omitted. Removing every second winding and rotating the middle machine <NUM>' may allow for the interlaced configuration depicted in <FIG>.

As shown, the windings of each adjacent machine <NUM>, <NUM>', <NUM>" are offset in such a manner that windings of adjacent machines cannot touch. This may provide an added benefit of reducing the possibility of phase-to-phase short circuits, which may occur if windings from adjacent machines are too closely packed together. As an additional advantage, the configuration of <FIG> may save axial space, which may be advantageous in applications in which space is limited or at a premium.

It should be appreciated that although <FIG> depicts an embodiment of machine system <NUM> with machines <NUM> in <NUM> planes, it is contemplated that some embodiments may include fewer than <NUM> machines <NUM> in parallel, and some embodiments may include more than <NUM> machines <NUM> in parallel, connected via rotor shafts <NUM> to define common rotors between machines.

As noted above, in some embodiments, machine systems <NUM>, <NUM>, <NUM> may include more than one gear <NUM>, <NUM> coupled to an individual rotor shaft <NUM>, <NUM>. <FIG> is a partial cross-sectional view of an electric machine system <NUM> with multiple gears affixed or connected to each rotor shaft <NUM>. It should be noted that although machine <NUM> is described with reference to machine <NUM>, the principles disclosed herein relating to machine <NUM> with multiple gears per rotor shaft may be applied to numerous electric machine systems (and in particular to machine system <NUM> described herein).

As shown in <FIG>, rotor shaft 816d interconnects each of rotors 802d, 802d', 802d". Gear 818d is connected to rotor shaft 816d adjacent to rotor 802d, and driving gear 818d' is connected to rotor shaft 816d adjacent to rotor 808d". Each of gears 818d, 818d' is configured to engage with central gears. As depicted, driving gear 818d engages with a first central gear <NUM>, and driving gear 818d' engages with a second central gear <NUM>'. Each of central gears <NUM>, <NUM>' are rotatably fixed to shaft <NUM>. As such, when rotor shaft 816d is caused to rotate by rotors 802d, 802d', 802d", both of gears 818d and 818d' are caused to drive central gears <NUM> and <NUM>', respectively. Thus, the net torque applied to central shaft <NUM> is the sum of the torque applied by gears 818d and 818d'. It will be appreciated that relative to configurations with only one gear 818d per rotor shaft 816d, roughly the same net torque will be produced by the rotors 802d, 802d', 802d". As such, if gears 818d, 818d' have the same dimensions and central gears <NUM>, <NUM>' have the same dimensions, the torque exerted by each gear 818d, 818d' would be expected to be roughly half of the torque applied by gear 818d in an embodiment with one gear (minus any additional losses caused by the extra weight of the additional gear, and the like). Therefore, the addition of second gear 818d' may result in the strain and stress on each gear 818d, 818d' being significantly reduced, which may allow for the use of less expensive materials which are less resistant to stress (e.g. plastic), and may require less ongoing maintenance (e.g. less oil).

Although <FIG> depicts two gears 818d, 818d' per collective rotor, it should be appreciated that other embodiments which involve more than two gears (e.g. additional central gears and additional gears 818d which are located between any of rotors 802d, 802d', 802d") are contemplated, and may further reduce the stress and strain experienced by gears.

It should be further noted that although <FIG> depicts an embodiment in which both central gears <NUM> and <NUM>' are fixed to the same central shaft <NUM>, it is contemplated that in other embodiments, central gear <NUM> may be fixed to a first input/output shaft <NUM>, and central gear <NUM>' may be fixed to a second input/output shaft <NUM>' which may rotate independently from first input/output shaft <NUM>. As such, some embodiments of machine <NUM> may be suitable for use in gearbox applications, without requiring the addition of a gearbox to machine <NUM>, which may provide numerous benefits relating to lower costs and reducing the weight and amounts of materials required for a given application.

<FIG> is a schematic partial cross-sectional view of an electric machine <NUM> system having an independent input shaft <NUM> and output shaft <NUM>'. Machine system <NUM> is similar to machine system <NUM> in many respects. Machine system <NUM> includes one or more collective rotors <NUM> (for simplicity, only one collective rotor <NUM> is shown). Rotor shaft <NUM> interconnects rotors <NUM>, <NUM>', <NUM>" of machines <NUM>, <NUM>', <NUM>" to define collective rotor <NUM>, and input gear <NUM> is fixed to an end of collective rotor <NUM> adjacent to first rotor <NUM>. Output gear <NUM>' is fixed to another end of collective rotor <NUM> adjacent to third rotor <NUM>". In some embodiments, collective rotors <NUM> have parallel rotational axes. In some embodiments, the collective rotors <NUM> may be disposed to define a circular array arrangement. Although <FIG> depicts machine <NUM> having <NUM> rotors per collective rotor, it will be appreciated that embodiments with as few as one electric machine rotor per collective rotor <NUM> are contemplated. Embodiments with more than <NUM> electric machine rotors per collective rotor <NUM> are also contemplated. In some embodiments, the electric machine rotors are axially spaced apart between the input gear <NUM> and output gear <NUM>'.

As depicted, input gear <NUM> is drivingly coupled to input shaft <NUM> via first central gear <NUM>. First central gear may be fixed to input shaft <NUM>. Output gear <NUM>' is drivingly coupled to output shaft <NUM>' via second central gear <NUM>'. Second central gear <NUM>' is coupled to output shaft <NUM>'. In some embodiments, input shaft <NUM> is connected to a gas turbine. In some embodiments, output shaft <NUM>' is connected to a propeller or fan. It will be appreciated that the speed at which input shaft rotates may be substantially different (faster or slower) from the speed at which output shaft rotates. Normally, a separate gearbox may be used to transfer mechanical energy from one rotating gear to another. However, in the embodiment shown in <FIG>, no separate gearbox is required.

Instead, the sizes of first central gear <NUM>, input gear <NUM>, output gear <NUM>' and second central gear <NUM>' may be chosen such that the gear ratios allow for a rotation at the input shaft <NUM> to result in a rotation in or around a desired speed at output shaft <NUM>'. Such rotation is achieved by the rotation of input shaft <NUM> causing first central gear <NUM> to rotate. The rotation of first central gear <NUM> causes input gear <NUM> to rotate at an angular speed. Output gear <NUM>' shares rotor shaft <NUM> with input gear <NUM>, and so the output gear <NUM>' will also rotate at the same angular speed as input gear <NUM>. Output gear <NUM>' is coupled to second central gear <NUM>', and so the rotation of output gear <NUM>' causes the rotation of second central gear <NUM>', thereby causing the resulting rotation of output shaft <NUM>'.

In some embodiments, electrical rotors <NUM>, <NUM>', <NUM>" in machine system <NUM> are operable in a generating mode and in a motoring mode. When electrical rotors <NUM>, <NUM>', <NUM>" are operating in a motoring mode, the rotor shafts <NUM> may be indexed to provide a torque phase offset relative to each other. When electrically powered, the mechanical power at the input shaft <NUM> is transmitted through machine <NUM> in a manner similar to that of a gearbox. When electrical rotors <NUM>, <NUM>', <NUM>" are electrically powered, the power output to output shaft <NUM>' is the sum of the mechanical power at input shaft <NUM> and the output power of machines <NUM>, <NUM>', <NUM>". As such, in situations where the mechanical input power at shaft <NUM> is insufficient to achieve the desired output at output shaft <NUM>', machines <NUM>, <NUM>', <NUM>" may be electrically powered so as to provide additional output power to output shaft <NUM>'.

In addition, the machine system <NUM> can act as an in-line generator to convert some of the mechanical input power at shaft <NUM> to electrical current at windings <NUM>, <NUM>', <NUM>". This electrical power may be used for various purposes, such as, for example, aircraft electrical systems, charging batteries, or the like. In some embodiments (e.g. turbine engines), the generated electrical power may be used to accelerate or apply positive torque to the high pressure spool or compressor spool of an engine core.

Contrary to conventional hybrid electrical applications, the assistance provided by machine <NUM> is not applied on a high-speed output shaft or to an auxiliary pad of a reduction gearbox. Instead, machine <NUM> may act as a gearbox with an electric machine embedded therein.

Claim 1:
An electric machine system (<NUM>; <NUM>) comprising:
a first electric machine (<NUM>; <NUM>) configured to drive a load (<NUM>), the first electric machine (<NUM>; <NUM>) having a plurality of first rotors (<NUM>; <NUM>),
wherein the first electric machine (<NUM>; <NUM>) has a first common stator (<NUM>; <NUM>) and one or more first windings (<NUM>; <NUM>) circumferentially spaced apart on the first common stator (<NUM>; <NUM>), the first rotors (<NUM>; <NUM>) configured to be driven using electric power having a single first phase, characterized in that the electric machine system (<NUM>; <NUM>) further comprises:
a second electric machine (<NUM>'; <NUM>') configured to drive the load (<NUM>), the second electric machine (<NUM>'; <NUM>') having a plurality of second rotors (<NUM>'; <NUM>'), wherein the second electric machine (<NUM>'; <NUM>') has a second common stator (<NUM>; <NUM>) and one or more second windings (<NUM>; <NUM>) circumferentially spaced apart on the second common stator (<NUM>; <NUM>), the second rotors (<NUM>'; <NUM>') configured to be driven using electric power having a single second phase, the second phase different from the first phase; and
a plurality of shafts (<NUM>; <NUM>), each shaft (<NUM>; <NUM>) connecting one of the first rotors (<NUM>; <NUM>) with one of the second rotors (<NUM>'; <NUM>'), the one of the first rotors (<NUM>; <NUM>) being coaxial with and axially spaced apart from the one of the second rotors (<NUM>'; <NUM>').