Abstract:
An electromagnetic propulsion system includes a plurality of primary windings and a permanent magnet arranged to move with respect to the plurality of primary windings. A secondary winding of the system is disposed in a non-moving relationship with the permanent magnet. An excitation energy is applied to the plurality of primary windings for creating a magnetic field that includes a base component and low frequency harmonic components. The base component substantially contributes toward motion between the plurality of primary windings and the permanent magnet and the low frequency harmonic components substantially contributes toward generating an electro-motive force in the secondary winding based on displacement between the plurality of primary windings and the permanent magnet.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Application No. 62/209,814 filed Aug. 25, 2015, the entire contents of which is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to electromagnetic propulsion systems, and more particularly to propulsion systems having wireless power transfer systems. 
         [0003]    Electromagnetic propulsion systems operate to move a first structure relative to a stationary second structure generally through magnetic levitation. Without tethers, it is difficult to provide on-board power to the moving first structure. 
         [0004]    Self-propelled elevator systems, as one non-limiting example, may utilize such magnetic propulsion systems. Such ropeless elevator systems are useful in certain applications (e.g., high rise buildings) where the mass of the ropes for a roped system is prohibitive and/or there is a need for multiple elevator cars in a single hoistway. Elevator cars typically need power for ventilation, lighting systems, operation of doors and brakes, control units, communication units and to recharge batteries installed, for example, on an elevator car controller. Moreover, elevator cars may require back-up systems in case of a power failure. Existing systems use moving cables or current collectors/sliders to connect a moving elevator car with power lines distributed along the elevator hoistway. 
       SUMMARY 
       [0005]    An electromagnetic propulsion system according to one, non-limiting, embodiment of the present disclosure includes a plurality of primary windings; a permanent magnet arranged to move with respect to the plurality of primary windings; a secondary winding disposed in a non-moving relationship with the permanent magnet; and an excitation energy applied to the plurality of primary windings for creating a magnetic field including a base component and low frequency harmonic components, and wherein the base component substantially contributes toward motion between the plurality of primary windings and the permanent magnet and the low frequency harmonic components contributes toward generating an electro-motive force in the secondary winding based on displacement between the plurality of primary windings and the permanent magnet. 
         [0006]    Additionally to the foregoing embodiment, the magnetic field includes a high frequency component that contributes toward generating the electro-motive force in the secondary winding and based on variation with respect to time. 
         [0007]    In the alternative or additionally thereto, in the foregoing embodiment, the permanent magnet and the secondary winding are carried by an elevator car which is propelled in response to the excitation energy. 
         [0008]    In the alternative or additionally thereto, in the foregoing embodiment, the low frequency harmonics component and the high frequency component are used to transfer electrical power from the plurality of primary windings to the elevator car through the secondary winding. 
         [0009]    In the alternative or additionally thereto, in the foregoing embodiment, the electromagnetic propulsion system is a linear electromagnetic motor. 
         [0010]    In the alternative or additionally thereto, in the foregoing embodiment, the electromagnetic propulsion system is a compound motion electromagnetic motor. 
         [0011]    An elevator system according to another, non-limiting, embodiment includes an elevator car arranged to move along a hoistway defined by a structure; an electrically powered subsystem carried by the elevator car; a plurality of primary windings engaged to the structure and positioned along the hoistway; a permanent magnet coupled to the elevator car, the plurality of primary windings and the permanent magnet configured to impart motion to the elevator car; an excitation energy applied to the plurality of primary windings for creating a magnetic field including a base component and a low frequency harmonics component, and wherein the base component substantially contributes toward the motion of the elevator car; and a secondary winding coupled to the elevator car and disposed adjacent to the permanent magnet, and wherein the low frequency harmonics component generates an electro-motive force in the secondary winding based on displacement between the plurality of windings and the elevator car for providing electrical power to the electrically powered subsystems. 
         [0012]    Additionally to the foregoing embodiment, the magnetic field includes a high frequency component that contributes toward generating the electro-motive force in the secondary winding and based on variation with respect to time. 
         [0013]    In the alternative or additionally thereto, in the foregoing embodiment, the electrically powered subsystem includes at least one of a battery, a ventilation unit, a lighting system, door operation unit, brake unit, display unit, a control unit, and a communication unit. 
         [0014]    In the alternative or additionally thereto, in the foregoing embodiment, the elevator system includes a controller configured to sequentially control the energization of the plurality of primary windings. 
         [0015]    In the alternative or additionally thereto, in the foregoing embodiment, the elevator system is ropeless. 
         [0016]    In the alternative or additionally thereto, in the foregoing embodiment, the elevator system includes a power converter disposed in the elevator car and configured to convert an induced voltage and current from the secondary winding to suitable AC or DC voltage and current. 
         [0017]    The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. However, it should be understood that the following description and drawings are intended to be exemplary in nature and non-limiting. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiments. The drawings that accompany the detailed description can be briefly described as follows: 
           [0019]      FIG. 1  depicts a multicar elevator system in an exemplary embodiment; 
           [0020]      FIG. 2  is a top down view of a car and portions of a linear propulsion system in an exemplary embodiment; 
           [0021]      FIG. 3  is a schematic of the linear propulsion system; 
           [0022]      FIG. 4  is a schematic of the elevator system with a wireless power transfer system; 
           [0023]      FIG. 5  is a graph of total excitation currents; 
           [0024]      FIG. 6  is a graph of base frequency and high frequency components of the total excitation currents in  FIG. 5 ; 
           [0025]      FIG. 7  is a graph of a field produced by the high frequency components; 
           [0026]      FIG. 8  is a block diagram illustrating magnetic field components produced by energized primary windings of the propulsion system; and 
           [0027]      FIG. 9  is a schematic of a second embodiment of a propulsion system with a wireless power transfer system. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    The following patent applications assigned to the same assignee and filed on the same day as the present disclosure are herein incorporated by reference in their entirety (identified via docket numbers: 79766US01 (U320411US); 78887US01 (U320410US); 78800US01 (U320415US); and 77964US01 (U320409US). 
         [0029]      FIG. 1  depicts a self-propelled or ropeless elevator system  20  in an exemplary embodiment that may be used in a structure or building  22  having multiple levels or floors  24 . Elevator system  20  includes a hoistway  26  having boundaries defined by the structure  22  and at least one car  28  adapted to travel in the hoistway  26 . The hoistway  26  may include, for example, three lanes  30 ,  32 ,  34  each extending along a respective central axis  35  with any number of cars  28  traveling in any one lane and in any number of travel directions (e.g., up and down). For example and as illustrated, the cars  28  in lanes  30 ,  34 , may travel in an up direction and the cars  28  in lane  32  may travel in a down direction. 
         [0030]    Above the top floor  24  may be an upper transfer station  36  that facilitates horizontal motion to elevator cars  28  for moving the cars between lanes  30 ,  32 ,  34 . Below the first floor  24  may be a lower transfer station  38  that facilitates horizontal motion to elevator cars  28  for moving the cars between lanes  30 ,  32 ,  34 . It is understood that the upper and lower transfer stations  36 ,  38  may be respectively located at the top and first floors  24  rather than above and below the top and first floors, or may be located at any intermediate floor. Yet further, the elevator system  20  may include one or more intermediate transfer stations (not illustrated) located vertically between and similar to the upper and lower transfer stations  36 ,  38 . 
         [0031]    Referring to  FIGS. 1 through 3 , cars  28  are propelled using a linear propulsion system  40  having at least one, fixed, primary portion  42  (e.g., two illustrated in  FIG. 2  mounted on opposite sides of the car  28 ), moving secondary portions  44  (e.g., two illustrated in  FIG. 2  mounted on opposite sides of the car  28 ), and a control system  46  (see  FIG. 4 ). The primary portion  42  (i.e. stator) includes a plurality of windings  48  mounted at one or both sides of the lanes  30 ,  32 ,  34  in the hoistway  26 . Each secondary portion  44  may include two rows of opposing permanent magnets  50 A,  50 B mounted to the car  28 . Primary portion  42  is supplied with drive excitations from the control system  46  to generate a magnetic flux that imparts a force on the secondary portions  44  to control movement of the cars  28  in their respective lanes  30 ,  32 ,  34  (e.g., moving up, down, or holding still). The plurality of windings  48  of the primary portion  42  are generally located between and spaced from the opposing rows of permanent magnets  50 A,  50 B. It is contemplated and understood that any number of secondary portions  44  may be mounted to the car  28 , and any number of primary portions  42  may be associated with the secondary portions  44  in any number of configurations. 
         [0032]    Referring to  FIG. 3 , the control system  46  may include power sources  52 , power converters  54  (e.g. motor or propulsion drives), buses  56  and a controller  58 . The power sources  52  are electrically coupled to the power converters  54  via the buses  56 . In one non-limiting example, the power sources  52  may be direct current (DC) or alternating current (AC) power sources. DC power sources  52  may be implemented using storage devices (e.g., batteries, capacitors), and may be active devices that condition power from another source (e.g., rectifiers connected to power grid, generators, etc.). The power converters  54  may receive DC or AC power from the buses  56  and may provide drive excitations to the primary portions  42  of the linear propulsion system  40 . Each power converter  54  may be a converter that converts DC or AC power from bus  56  to a multiphase (e.g., three phases illustrated in  FIG. 3 , and two phases illustrated in  FIG. 4 ) drive excitation provided to a respective section of the primary portions  42 . The primary portion  42  may be divided into a plurality of modules or sections, with each section associated with a respective power converter  54 . 
         [0033]    The controller  58  provides control signals to each of the power converters  54  to control generation of the drive excitation. Controller  58  may use pulse width modulation (PWM) control signals to control generation of the drive excitations by the power converters  54 . Controller  58  may be implemented using a signal processor-based device programmed to generate the control signals. The controller  58  may be distributed as a part of each drive  54  to generate control signal for corresponding drive. The controller  58  may also be part of an elevator control system or elevator management system. Elements of the control system  46  may be implemented in a single, integrated module, and/or be distributed along the hoistway  26 . 
         [0034]    Referring to  FIG. 4 , a wireless power transfer system  60  of the elevator system  20  may be used to power loads or elevator car subsystems  62  in or on the elevator car  28 . The power transfer system  60  may be an integral part of the control system  46  thereby sharing various components such as the controller  58  (see  FIG. 3 ), buses  56 , power source  52 , power converters  54 , primary portion(s)  42  and other components. The subsystems  62  may include batteries or energy storage devices, a ventilation unit, a lighting system, a door operation unit, brake unit, display unit, a control unit, a communication unit, and others. The subsystems  62  may be alternating current (AC) loads, such as fans of the ventilation unit and others, utilizing a traditional power frequency such as, for example, about 60 Hz. Alternatively, or in addition thereto, the subsystems  62  may include direct current (DC) loads, such as the display unit. The international patent application WO 2014/189492 published under the Patent Cooperation Treaty on Nov. 27, 2014, filed on May 21, 2013, and assigned to Otis Elevator Company of Farmington, Conn., is herein incorporated by reference in its entirety. 
         [0035]    Referring to  FIGS. 4 and 5 , the primary assembly  42  may include a plurality of primary windings  64  at a first phase and a plurality of primary windings  66  at a second phase offset from the first phase. The power converter  54  (e.g. switching power converter controlled with PWM) receives power from the power supply  52  and may convert the power to a predetermined base frequency, voltage, number of phases (two illustrated in  FIG. 4 ) and controlled excitation current of the primary windings  64 ,  66 . The energy from the converter  54  is outputted to the primary windings  64 ,  66 . The total excitation current received by each primary winding  64 ,  66  is illustrated in  FIG. 5 . The mechanical propulsion is produced by the low frequency (i.e., base frequency) component of the excitation, which is generally at a low frequency that may be in a range of about 0 Hz to 100 Hz (i.e., wherein 0 Hz may be when the car is held at a stationary position by the excitation of the primary windings). 
         [0036]    Generally inherent in the switching power converter  54  is the modulation of switches that may produce switching frequency ripple. The switching frequency ripple components are utilized by the wireless power transfer system  60 . More specifically and as best shown in  FIG. 6 , the total excitation current (i x ) of the winding  64  may be broken down into a base frequency component (i xb ) at the low base frequency and a ripple or switching frequency component (i xs ) at a much higher excitation switching frequency (i.e. switching frequency ripple) that may be in a range of about 1 kHz to 100 kHz. Similarly, the total excitation current (i y ) of the winding  66  may be broken down into a base frequency component (i yb ) at the low frequency and a switching frequency component (i ys ) at the much higher excitation switching frequency. The base frequency components (i yb ) of the respective total excitation currents (i x ), (i y ) may generally be used by the propulsion system  40  to levitate and/or propel the elevator car  28 . The switching frequency components (i xs ), (i ys ) may be used by the wireless power transfer system  60  to power the elevator car loads  62 . Referring to  FIG. 7 , a graph illustrates the probable resultant field produced by the switching frequency components (i xs ), (i ys ). Alternatively, or in addition to this excitation the primary winding can be supplied with a high frequency excitation, which is much greater than the base frequency but lower than the switching frequency, to transfer wireless power to the secondary. 
         [0037]    The wireless power transfer system  60  may further include components generally in or carried by the elevator car  28 . Such components may include a secondary winding  68  configured to be induced with a voltage or current when the energized primary windings  64 ,  66  are proximate thereto, a resonant component  70  that may be active and/or passive, and a power converter  72 . The secondary winding  68  may induce a current when the winding is proximate to the energized primary windings  64 ,  66 , and may be induction based, or resonance based constructed to resonate generally at the frequency of the excitation switching ripple or at the harmonic components of the switching frequency ripple. Although not illustrated, the secondary windings  68  may have a pole pitch that is not equal to a pole pitch of the primary windings  64 ,  66 . The secondary windings  68  of the power transfer system  60  may generally wrap about one or both of the permanent magnets  50 A,  50 B of the secondary portion  44  of the propulsion system  40 . 
         [0038]    The resonant component  70  receives energy from the secondary winding  68  and may be passive or active. As a passive resonant component  70 , the component is generally a capacitor and capable of storing or operating on AC power. As an active resonant component  70 , the component  70  is configured to mitigate the effects of a weak or variable coupling factor (i.e., varies when the secondary winding  68  passes the primary windings  64 ,  66 ). That is, the resonant component  70  may function to level-out the induced output current and voltage from the secondary winding  68 . 
         [0039]    The power converter  72  in the elevator car  28  is configured to receive high frequency power from the resonant component  70 . The converter  72  may reduce the high frequency power to a suitable low frequency power (e.g., low power frequency of 60 Hz or other) that is compatible with AC loads  62  in the elevator car  28 . The converter  72  may further function to convert the high frequency power to DC power, which is then stored in an energy storage device (not illustrated). An example of an energy storage device may be a type of battery. 
         [0040]    The ability to induce current in the secondary winding  68  at the high switching frequency (i.e., as oppose to low frequency) may optimize the efficiency of induced power transfer from the primary windings  64 ,  66  to the secondary winding  68 . Moreover, the high switching frequency generally facilitates the reduction in size of many system components such as the secondary winding  68 , the resonant component  70  and the converter  72  amongst others. Reducing the size of components improves packaging of the system and may reduce elevator car  28  weight. 
         [0041]    The secondary winding  68  may be designed and deployed such that the base frequency components (i xb ), (i yb ) do not create any variable field upon the secondary winding, and only the high switching frequency field (i.e. produced by converter switching) produces a varying field across the secondary winding to enable wireless power transfer. The elevator system  20  is highly reliable, safe, and is not limited by the mechanical and electrical limitations of a contact based power transfer system. The elevator system  20  may utilize existing excitation arrangements on the stationary side for the wireless power transfer function. Moreover, the system  20  may utilize the ripple components produced by the switching of the power converter  54  which may already exist in typical systems. The system  20  is relatively simple and robust, and may not require additional switching or modulation of the primary excitation, and additional power converter and winding on the stationary side of the system. The present disclosure may also be utilized for any information exchange between the stationary and moving sides. 
         [0042]    Referring to  FIG. 8 , a method of utilizing the wireless power transfer system  60  applies the theory of induction of electro-motive force due to the change of magnetic flux with respect to space and time. As previously described electrical power may be transferred wirelessly from the primary windings  44 ,  46  to the secondary windings  68  by suitable excitation on the primary windings  44 ,  46 . The total magnetic field (B TF )  80  created by the energized primary windings may consist of three components: (1) a base component (B BF ) 82, (2) low frequency harmonic components (B LF ) 84, and (3) high frequency components (B HF )  86 . The components  82 ,  84 ,  86  are expressed in the following equation: 
         [0000]        B   TF   =B   BF   +B   LF   +B   HF   (1)
 
         [0043]    The base frequency harmonics component  82  interacts with the magnetic field of the permanent magnets  50 A,  50 B to create a force for propulsion. The low frequency harmonics component  84  creates an electro-motive mainly due to a change in position and may be expressed by the following equation: 
         [0000]        e   LF =dB LF   /dx   (2)
 
         [0044]    The high frequency component  86  creates an electro-motive force mainly due to its variation with respect to time, and can be expressed by the following equation: 
         [0000]        e   HF =dB HF   /dt   (3)
 
         [0045]    Therefore, the low frequency harmonics component  84  and the high frequency component  86 , created by the primary windings  44 ,  46  may be utilized to transfer electrical power wireless to the elevator car  28 . In addition to the dynamic condition, under static conditions when the elevator car  28  is stationary, wireless power transfer may be achieved by modifying the base flux (eq. 1) and by utilizing the high frequency component  86  (eq. 3). The low frequency harmonic components  84  may be produced by using the combination of winding structure and excitation currents. Power transfer using low frequency harmonic components  84  may produce pulsating forces for set of primary and secondary windings. Such pulsating forces can be effectively cancelled on the car by proper phase displacement between the low frequency components in various sets of primary secondary winding. It is further contemplated and understood that the wireless transfer methods may be applicable to any type of electromagnetic dynamic system with linear, rotary and/or compound motions. 
         [0046]    Low frequency harmonic components  84  for wireless power transfer can be created by using the combination of winding structure and excitation currents. Power transfer using low frequency harmonic components  84  may produce pulsating forces for set of primary and secondary windings. Such pulsating forces can be effectively cancelled on the car  28  by proper phase displacement between the low frequency harmonic components  84  in various sets of primary secondary winding. 
         [0047]    Referring to  FIG. 9 , a second embodiment of a propulsion system is illustrated wherein like components to the first embodiment have like element numbers except with the addition of a prime symbol suffix. A propulsion system  40 ′ may not be linear and instead may be a compound motion electromechanical motor that may include rotation (i.e. rotating motor), or a combination of rotary and linear motion. A wireless power transfer system  60 ′ may be integral to the propulsion system  40 ′. It is further contemplated and understood that the systems  40 ′,  60 ′ may not be limited to elevators and may be applied to any variety of applications that may require wireless power transfer to a moving structure  28 ′ from a stationary structure  22 ′. 
         [0048]    While the present disclosure is described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the present disclosure. In addition, various modifications may be applied to adapt the teachings of the present disclosure to particular situations, applications, and/or materials, without departing from the essential scope thereof. The present disclosure is thus not limited to the particular examples disclosed herein, but includes all embodiments falling within the scope of the appended claims.