Abstract:
An elevator system includes an elevator car having an elevator car subsystem; a guide rail to guide the elevator car along a hoistway; primary windings positioned along the hoistway; permanent magnets coupled to the elevator car, the primary windings and permanent magnets defining a linear motor for imparting motion to the elevator car in response to a drive signal; and secondary windings coupled to the elevator car, the secondary windings generating a current to power the elevator car subsystem.

Description:
FIELD OF INVENTION 
       [0001]    The subject matter disclosed herein relates generally to the field of elevators, and more particularly, to a wireless power supply for a self-propelled elevator. 
       BACKGROUND 
       [0002]    Self-propelled elevator systems, also referred to as 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, control units, communication units and to recharge batteries installed, for example, on an elevator car controller. Existing systems use moving cables or current collectors/sliders to connect a moving elevator car with power lines distributed along the elevator hoistway. 
       SUMMARY 
       [0003]    According to an exemplary embodiment of the invention, an elevator system includes an elevator car having an elevator car subsystem; a guide rail to guide the elevator car along a hoistway; primary windings positioned along the hoistway; permanent magnets coupled to the elevator car, the primary windings and permanent magnets defining a linear motor for imparting motion to the elevator car in response to a drive signal; and secondary windings coupled to the elevator car, the secondary windings generating a current to power the elevator car subsystem. 
         [0004]    According to another exemplary embodiment of the invention, a wireless power supply for an elevator car includes primary windings; permanent magnets for coupling to an elevator car, the primary windings and permanent magnets defining a linear motor for imparting motion to the elevator car in response to a drive signal; and secondary windings for coupling to the elevator car, the secondary windings generating a current to power an elevator car subsystem. 
         [0005]    According to another exemplary embodiment of the invention, a linear motor system includes a plurality of permanent magnets, configured to be attached to a movable component; a plurality of primary windings configured to impart motion to the permanent magnets; and a plurality of secondary windings configured to be coupled to the movable component, wherein the plurality of secondary windings are configured to passively generate an electrical current when the movable component moves in relation to the plurality of primary windings. 
         [0006]    Other aspects, features, and techniques of embodiments of the invention will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Referring now to the drawings wherein like elements are numbered alike in the FIGURES: 
           [0008]      FIG. 1  depicts an elevator system having a wireless power supply in an exemplary embodiment; 
           [0009]      FIG. 2  is a top view of a linear motor and wireless power supply in an exemplary embodiment; 
           [0010]      FIG. 3  is a perspective view depicting a winding distribution for the primary windings and secondary windings in an exemplary embodiment; 
           [0011]      FIG. 4  is a perspective view depicting primary windings on a flat core in an exemplary embodiment; and 
           [0012]      FIG. 5  is a schematic diagram of an elevator system in an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]      FIG. 1  depicts an elevator system  10  having a wireless power supply in an exemplary embodiment. Elevator system  10  includes an elevator car  12  that travels in a hoistway  14 . Elevator car  12  travels along one or more guide rails  16  extending along the length of hoistway  14 . Elevator system  10  employs a linear motor having primary windings  18  provided along guide rails  16 . Primary windings  18  include a plurality of coils coupled to the guide rails  16 . Each guide rail  16  on either side of elevator car  12  may include primary windings  18 . The primary windings  18  serve as stator windings of a permanent magnet synchronous motor to impart motion to elevator car  12 . Primary windings  18  may be arranged in three phases. Primary windings  18  may be located separate from guide rails  16  in exemplary embodiments. According to further exemplary embodiments, windings  18  may be used as guide rails  16  or incorporated into the guide rails  16 . According to an exemplary embodiment a single stator may be used instead of multiple stators. Further, multiple stators may be configured on opposite sides of an elevator car  12  as shown in  FIG. 1 , or they may have different configurations, for example, multiple stators may be positioned adjacent a single side of the elevator car  12 . 
         [0014]    Controller  20  provides drive signals to the primary windings  18  to impart motion to the elevator car  12 . Controller  20  may be implemented using a general-purpose microprocessor executing a computer program stored on a storage medium to perform the operations described herein. Alternatively, controller  20  may be implemented in hardware (e.g., ASIC, FPGA) or in a combination of hardware/software. Controller  20  may also be part of an elevator control system. Controller  20  may include power circuitry (e.g., an inverter or drive) to power the primary windings  18 . 
         [0015]      FIG. 2  is top view showing the linear motor and wireless power supply in an exemplary embodiment. A single guide rail  16  is shown, but it is understood that both guide rails  16  and both sides of elevator car  12  may be configured as shown. As shown in  FIG. 2 , guide rail  16  supports primary windings  18 . Coils of the primary windings  18  may be formed about ferromagnetic cores. Permanent magnets  22  are mounted to elevator car  12 , and are positioned on opposite sides of the primary windings  18 . The primary windings  18  and permanent magnets  22  form a permanent magnet synchronous motor to impart motion to elevator car  12 . 
         [0016]    Elevator car  12  also includes secondary windings  24  mounted to a cabin of elevator car  12 , juxtaposed the primary windings  18 . Secondary windings  24  include a plurality of coils coupled to the elevator car  12 . Coils of the secondary windings  24  may be formed about ferromagnetic cores. Secondary windings  24  are not used for propulsion of elevator car  12 , but rather as a secondary winding of an air core transformer formed by primary windings  18  and secondary windings  24 . Drive signals applied to primary windings  18  produce leakage flux that induces an electromotive force in secondary windings  24  to generate a current in the secondary windings  24 , as described in further detail herein. 
         [0017]      FIG. 3  is a perspective view depicting a winding distribution for the primary windings  18  and secondary windings  24  in an exemplary embodiment. Primary windings  18  and secondary windings  24  each include a number of coils. In the embodiments of  FIG. 2  and  FIG. 3 , the primary windings  18  are formed about a generally rectangular core or pipe  19 . Both the primary windings  18  and secondary windings  24  include three phases, illustrated as A, B and C. The coils of the primary windings  18  and secondary windings  24  are arranged in a repeating pattern. As shown in  FIG. 3 , the coils of primary windings  18  and secondary windings  24  follow a phase pattern of negative C phase, c, positive A phase, A, negative B phase, b, positive C phase, C, negative A phase, a, and positive B phase, B. 
         [0018]    Primary windings  18  may also be formed on a face of a flat stator core  21  as shown in  FIG. 4 . In such embodiments, permanent magnets  22  and secondary winding  18  are collocated on a side wall of elevator car  12 , facing primary windings  18 . The phase pattern of the coils making up primary windings  18  is shown in  FIG. 4 , and is similar to that in  FIG. 3 . As shown in  FIG. 4 , the coils of primary windings  18  (and the secondary windings  24 ) follow a phase pattern of negative C phase, c, positive A phase, A, negative B phase, b, positive C phase, C, negative A phase, a, and positive B phase, B. The current direction in each coil is also depicted in  FIG. 4 . 
         [0019]      FIG. 5  is a high level schematic diagram of the elevator system  10 . Controller  20  provides three-phase drive signals to the primary windings  18 . The interaction between primary windings  18  and permanent magnets  22  imparts motion elevator car  12 . The permanent magnets  22  and secondary windings  24  mounted to elevator car  12  move with synchronous speed relative to the primary windings  18 . The speed depends on the fundamental frequency of the electromagnetic field excited by the primary windings  18 . Coils of the secondary windings  24  have the same pole pitch as coils of the primary windings  18 . Secondary windings  24  include individual coils having the same longitudinal dimension as individual coils of primary winding  18 . There is no electromotive force in the secondary windings  24  induced by the fundamental frequency of the primary electromagnetic field during the movement of the elevator car  12  with synchronous speed (i.e., a speed produced by the fundamental frequency of the electromagnetic field generated by primary winding). Electromotive forces, however, are induced in the secondary windings  24  by the fundamental frequency of the drive signal (e.g., PWM carrier signal) from controller  20 . 
         [0020]    The secondary windings  24  are connected to a rectifier  30  to convert the AC current to DC current. The output of rectifier  30  is provided to one or more elevator car subsystems, including a battery  32 , ventilation unit  34 , lighting system  36 , control unit  38  and communication unit  40 . It is understood that rectifier  30  may provide power to a variety of elevator car subsystems, and the components in  FIG. 3  are exemplary. According to further exemplary embodiments, the output of rectifier  30  may be stored locally on the elevator car  12  for use as emergency power. 
         [0021]    Embodiments enable wireless energy transfer to a moving elevator car of a self-propelled elevator. This eliminates the need for moving cables or current collectors/sliders for connecting a moving elevator car with power lines distributed along the elevator hoistway. The secondary windings also provide an electromagnetic shielding barrier between primary windings of the linear motor and the interior of the elevator car. 
         [0022]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. While the description of the present invention has been presented for purposes of illustration and description, it is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications, variations, alterations, substitutions, or equivalent arrangement not hereto described will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. Additionally, while the various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments and that various aspects of the invention, although described in conjunction with one exemplary embodiment may be used or adapted for use with other embodiments even if not expressly stated. Accordingly, the invention is not to be seen as being limited by the foregoing description, but is only limited by the scope of the appended claims.