Abstract:
An elevator system includes an elevator car; a machine to impart motion to the elevator car; a brake to stop rotation of the machine, the brake comprising a first coil and a second coil, wherein removing power from the first coil and the second coil applies the brake to the machine; and a controller in communication with the brake, the controller configured to connect the first coil and the second coil in one of a first electrical configuration and a second electrical configuration.

Description:
BACKGROUND 
       [0001]    The subject matter disclosed herein relates generally to the field of elevator systems, and more particularly to controlling an electrical configuration of coils in an elevator brake to control a braking time. 
         [0002]    In existing elevator systems, a machine drives a traction sheave to impart motion to an elevator car. A brake is used to stop rotation of the traction sheave and halt motion of the elevator car. Typically, the brake includes a single electrical coil which drops immediately in an emergency stop. Due to the high instantaneous brake torque, the car may stop quickly, causing discomfort to passengers. 
       BRIEF SUMMARY 
       [0003]    According to one embodiment, an elevator system includes an elevator car; a machine to impart motion to the elevator car; a brake to stop rotation of the machine, the brake comprising a first coil and a second coil, wherein removing power from the first coil and the second coil applies the brake to the machine; and a controller in communication with the brake, the controller configured to connect the first coil and the second coil in one of a first electrical configuration and a second electrical configuration. 
         [0004]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein the first electrical configuration comprises the first coil and second coil in electrical parallel. 
         [0005]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein the second electrical configuration comprises the first coil and second coil in electrical series. 
         [0006]    In addition to one or more of the features described above, or as an alternative, further embodiments may include a brake management switch connected to the first coil and the second coil, the controller controlling the brake management switch to connect the first coil and the second coil in one of the first electrical configuration and the second electrical configuration. 
         [0007]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein the brake management switch comprises a relay. 
         [0008]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein the controller is configured to determine an operating mode of the elevator system, the controller configured to connect the first coil and the second coil in one of the first electrical configuration and the second electrical configuration in response to the operating mode. 
         [0009]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein the controller is configured to connect the first coil and the second coil in electrical parallel in response to determining that the operating mode of the elevator system comprises a motoring mode. 
         [0010]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein the controller is configured to connect the first coil and the second coil in electrical series in response to determining that the operating mode of the elevator system comprises a regenerative mode. 
         [0011]    Accordingly to another embodiment, a method of controlling an elevator brake having a first coil and a second coil includes determining an operating mode of the elevator system; and connecting the first coil and the second coil in one of a first electrical configuration and a second electrical configuration in response to the operating mode. 
         [0012]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein the connecting comprises connecting the first coil and the second coil in electrical parallel in response to determining that the operating mode of the elevator system comprises a motoring mode. 
         [0013]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein the connecting comprises connecting the first coil and the second coil in electrical series in response to determining that the operating mode of the elevator system comprises a regenerative mode. 
         [0014]    Technical effects of embodiments of the present disclosure include the ability to control the braking time of an elevator brake by altering an electrical configuration of coils in the brake. 
         [0015]    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. It should be understood, however, that the following description and drawings are intended to be illustrative and explanatory in nature and non-limiting. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The foregoing and other features, and advantages of the disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which like elements are numbered alike in the several FIGURES: 
           [0017]      FIG. 1  depicts an elevator system in an exemplary embodiment; 
           [0018]      FIG. 2  is a block diagram of components of an elevator system in an exemplary embodiment; 
           [0019]      FIG. 3  depicts a portion of a brake in an exemplary embodiment; 
           [0020]      FIG. 4  depicts coils of the elevator brake in a first electrical configuration in an exemplary embodiment; 
           [0021]      FIG. 5  depicts coils of the elevator brake in a second electrical configuration in an exemplary embodiment; 
           [0022]      FIG. 6  depicts brake coil current versus time for two brake coil configurations in an exemplary embodiment; and 
           [0023]      FIG. 7  depicts a flowchart of a process for controlling an elevator brake in an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]      FIG. 1  depicts an elevator system  10 , in accordance with an embodiment of the disclosure.  FIG. 2  is a block diagram of components of elevator system  10  in an exemplary embodiment. The elevator system  10  includes an elevator car  23  configured to move vertically upward and downward within a hoistway  51  along a plurality of car guide rails  61 . The elevator system  10  also includes a counterweight  28  operably connected to the elevator car  23  via a pulley system  26 . The counterweight  28  is configured to move vertically upward and downward within the hoistway  51 . The counterweight  28  moves in a direction generally opposite the movement of the elevator car  23 , as is known in conventional elevator systems. Movement of the counterweight  28  is guided by counterweight guide rails  63  mounted within the hoistway  51 . 
         [0025]    The elevator system  10  also includes an alternating current (AC) power source  12 , such as an electrical main line grid (e.g., 230 volt, single phase). The AC power is provided from the AC power source  12  to a switch panel  14 , which may include circuit breakers, meters, inverter/converter, etc. From the switch panel  14 , power is provided to a drive unit  20  ( FIG. 2 ), which produces drive signals for machine  22 . The drive unit  20  drives a machine  22  to impart motion to the elevator car  23  via a traction sheave  25  of the machine. The drive signals may be multiphase (e.g., three-phase) drive signals for a three-phase motor in the machine  22 . A brake  24  may be integrated with the machine  22  and be activated to stop the machine  22  and elevator car  23 . 
         [0026]    The drive unit  20  generates drive signals to for driving machine  22  in motoring mode. Motoring mode may occur when an empty elevator car is traveling downwards or a loaded elevator car is traveling upwards. Motoring mode refers to situations where the machine  22  is drawing current from the drive unit  20 . The system may also operate in a regenerative mode where power from machine  22  is fed back to the drive unit  20  and the AC power source  12 . Regenerative mode may occur when an empty elevator car is traveling upwards or when a loaded elevator car is traveling downwards. Regenerative mode refers to situations where the drive unit  20  receives current from the machine  22  (which acts as a generator) and supplies current back to the AC power source  12 . A near balance mode occurs when the weight of the elevator car  23  is about balanced with the weight of the counterweight  28 . Near balance mode operates similarly to motoring mode because the machine  22  is drawing current from the drive unit  20  to move the elevator car  23 . 
         [0027]    The controller  30  is responsible for controlling the operation of the elevator system  10 . The controller  30  may include a processor and an associated memory. The processor may be but is not limited to a single-processor or multi-processor system of any of a wide array of possible architectures, including field programmable gate array (FPGA), central processing unit (CPU), application specific integrated circuits (ASIC), digital signal processor (DSP) or graphics processing unit (GPU) hardware arranged homogenously or heterogeneously. The memory may be but is not limited to a random access memory (RAM), read only memory (ROM), or other electronic, optical, magnetic or any other computer readable medium. 
         [0028]      FIG. 3  depicts a portion of a brake  24  in an exemplary embodiment. The brake  24  includes a central hub  50  which has a through tapered passage  52  with a key slot  54 . The outer circumferential surface of the hub  50  is formed with splines so as to be fitted with a plurality of internally splined friction discs  58  of a suitable number, depending on the amount of braking torque which is required in each application. Each of the discs  58  carries an annular radially outwardly extending friction pad  60 . It will be appreciated from the above, that the hub  50 , discs  58  and pads  60  all rotate with the traction sheave  25 . The brake  24  also includes a magnet assembly  62  having coils  64 , and which are mounted on a base plate. An armature plate  68  is disposed adjacent to the magnet assembly  62 , followed by a series of annular brake plates  70 . It will be noted that the friction discs  60  and brake plates  70  are interleaved. The armature plate  68  is biased away from the magnet assembly  62  by a plurality of coil springs  72 . A plurality of guide dowels  80  dispersed circumferentially about the brake assembly  24  extend through the magnet assembly  62 , and the armature plate  68  and brake plates  70  to guide axial movement of these components relative to each other when the brake is set and released. It will be appreciated from the above that the discs  60  rotate with the traction sheave  25 , while the plates  70  remain relatively stationary. 
         [0029]    During normal operation of the elevator, the coils  64  are energized, and the armature plate  68  is magnetically held against the magnet assembly  62  causing the actuating springs  72  to be compressed. The brake  24  is thus in a “release” mode, and the friction discs  60  will be free to rotate, uninhibited by the plates  70 . In the event of a need to stop the car  23 , such as overspeed in either direction, or door-open movement of the cab away from a landing, power to the coils  64  will be switched off, and the coils  64  will deenergize. The actuating springs  72  will then move the armature plate  68  away from the magnet assembly  62  and toward the annular brake plates  70 . The force of the springs  72  is such that the plates  70  will clamp the discs  60  against further movement. Movement of the traction sheave  25  will thus be interrupted and the car  23  will stop its movement in the hoistway  51 . The brake  24  can be released by restoring power to the coil  64 . 
         [0030]    The brake  24  includes multiple coils  64 . Embodiments connect the coils  64  in a first electrical configuration or a second electrical configuration in order to control the braking time. Different braking times may be desired depending on the mode of operation of the elevator system  10 . For example, in a motoring mode the elevator system  10  may desire to employ a slower braking time. In regenerative mode, the elevator system  10  may desire to employ a faster braking time. 
         [0031]      FIG. 4  depicts coils  64   a  and  64   b  of the elevator brake in a first electrical configuration in an exemplary embodiment. The brake  24  includes a brake management switch  92  that connects the coils  64   a  or  64   b  in a first or second electrical configuration with respect to a voltage source  94  (e.g., 48 volts). The brake management switch  92  may be a relay having multiple poles, a series of electrically controlled switches (e.g., transistors), etc. With the brake management switch  92  in the first electrical configuration shown in  FIG. 4 , coils  64   a  and  64   b  are in electrical parallel. This places the full voltage of voltage source  94  across each coil  64   a  and  64   b . In the event the elevator car  23  needs to stop, controller  30  interrupts voltage source  94  so that no power is connected to coils  64   a  and  64   b . It takes time for the magnetic field of the coils  64   a  and  64   b  to dissipate to a point where the spring  72  overcomes the magnetic field of coils  64   a  and  64   b . Since both coils  64   a  and  64   b  receive the full voltage from voltage source  94 , then amount of time for the brake  24  to be applied is longer than in the second electrical configuration of  FIG. 5 . 
         [0032]      FIG. 5  depicts coils  64   a  and  64   b  of the elevator brake in a second electrical configuration in an exemplary embodiment. With the brake management switch  92  in the second electrical configuration shown in  FIG. 5 , coils  64   a  and  64   b  are in electrical series. This places the half the voltage of voltage source  94  across each coil  64   a  and  64   b . In the event the elevator car  23  needs to stop, controller  30  interrupts voltage source  94  so that no power is connected to coils  64   a  and  64   b . Since both coils  64   a  and  64   b  receive half the voltage from voltage source  94 , then amount of time for the brake to be applied is shorter than in the first electrical configuration of  FIG. 5 . 
         [0033]      FIG. 6  depicts brake coil current versus time for two brake coil configurations in an exemplary embodiment.  FIG. 6  depicts the occurrence of an emergency stop situation and the time for the brake coil current to dissipate to a level where the brake  24  stops traction sheave  25  (e.g., about −0.4 amps). As shown in  FIG. 6 , when the coils  64   a  and  64   b  are connected in series, the time for the coil current to decay to a brake applied limit is shorter than the time for the coil current to decay to the brake applied limit when the coils  64   a  and  64   b  are connected in parallel. This difference in time is shown as a brake delay in  FIG. 6 . 
         [0034]      FIG. 7  depicts a flowchart of a process for controlling an elevator brake in an exemplary embodiment. The process of  FIG. 7  may be implemented by controller  30  at the start or the initial part of an elevator run. At  200 , controller  30  determines the operating mode of the elevator system. The operating mode may be detected as motoring mode ( 202 ) or regenerative mode ( 204 ). The controller  30  may detect the operational mode based on direction of travel of the car  23  and the car load. The car load may be detected by in car load sensors, entrance/exit sensors, car-counterweight imbalance, etc. If the operational mode is detected as motoring mode, flow proceeds to  206  where the controller  30  controls the brake management switch  92  to place the coils  64   a  and  64   b  in the first electrical configuration of  FIG. 4 , i.e., the coils  64   a  and  64   b  in electrical parallel with the voltage source  94 . If the operational mode is detected as regenerative mode, flow proceeds to  208  where the controller  30  controls the brake management switch  92  to place the coils  64   a  and  64   b  in the second electrical configuration of  FIG. 5 , i.e., the coils  64   a  and  64   b  in electrical series with the voltage source  94 . At  210 , the elevator system is then operated in normal. 
         [0035]    Embodiments provide effective brake sequencing by controlling the voltage on each coil through circuit topology changes (e.g., parallel vs. series). The brake response time may be controlled based on operational mode using simple components. 
         [0036]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. While the description has been presented for purposes of illustration and description, it is not intended to be exhaustive or limited to embodiments 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 of the disclosure. Additionally, while the various embodiments have been described, it is to be understood that aspects may include only some of the described embodiments. Accordingly, the disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.