Field of the Disclosure

[0001] The present disclosure relates generally to elevators and, more particularly, to high performance elevator doors that consume minimal energy.

Background

[0002] One of the many factors affecting lift traffic handling performance is the time required to open and close elevator doors on any given level of a building. Indeed, reducing the time required to open and close the elevator doors is one of the simplest ways to improve lift traffic handling. As a result, many existing elevator systems now employ larger drives and larger motors that permit elevator doors to open and close more quickly. Larger drives and larger motors in turn require larger support mechanisms such as, for instance, larger power feeders supplying power to each elevator cab. Consequently, such elevator systems have become more expensive and consume more electricity, particularly during peak periods of lift traffic, which often overlap with electrical peak periods at which time electricity costs are most expensive.

[0003] Thus, there is a need for cost-efficient and energy-efficient elevator doors that offer high performance such that elevator doors can be opened and closed quickly to enhance lift traffic handling.

Summary

[0004] Elevator door operators open and close one or more cabin doors of an elevator cab. The elevator door operators may be mounted on each elevator cab. In many cases, hall doors are temporarily coupled to the cabin doors when the elevator cab arrives at a level of a building. The elevator door operator may comprise a drive having a bank of capacitors connected to a direct current (DC) bus of the drive. In some examples, the drive may be a variable voltage variable frequency (W ) drive. Those having ordinary skill in the art will recognize that WW drives may also be known by other names, such as variable frequency drive, variable speed drive, alternating frequency drive, or adjustable frequency drive, for example, which may also offer an ability to vary voltage and frequency. In any event, the capacitor bank may be sufficiently large to provide the high currents necessary for rapidly accelerating the elevator doors to their maximum speed. The drive may also comprise a rectifier for converting alternating current (AC) from a power source to DC and an inverter for converting the DC signal back to an AC signal having a sine-like waveform. The inverter may comprise, for instance, silicon-controlled rectifiers (SCR) transistors, gate turn-off thyristors (GTOs), and/or symmetrical gate- commutated thyristors (SGCTs) that behave like coordinated switches to create pulse width modulation (PWM) output that regulates frequency and voltage of a motor coupled to the drive.

[0005] The capacitor bank of the drive and a power supply external to the drive may be used to power the motor to begin accelerating the elevator doors from a fully closed position or, conversely, from a fully opened position. Shortly thereafter, a power supply control switch may disconnect the external power supply. Thus, the power required to continue accelerating the elevator doors and maintain the doors at a peak speed when opening or closing may then come solely from the capacitor bank.

[0006] As the elevator doors decelerate towards a fully closed position or a fully opened position, the motor may begin serving as a generator. Power generated by the motor may be stored in the capacitor bank of the DC bus, which was largely discharged previously as the elevator doors were accelerated. Once the elevator doors are fully opened or fully closed and/or as the elevator cab travels between levels of the building, the power supply may be reconnected by the power supply control switch to recharge the capacitor bank if need be. Put another way, the capacitor bank may be charged during elevator door deceleration and discharged during elevator door acceleration. Disconnecting the power supply during elevator door acceleration ensures that the capacitor bank is discharged and has capacity to absorb power generated by the motor upon elevator door deceleration. Otherwise, the capacitor bank of the DC bus may be overcharged and cause an over-voltage fault.

Brief Description of the Drawings

[0007] Figure 1 is a schematic view of an example drive coupled to an example motor configured to open and close one or more elevator doors.

[0008] Figure 2 is a chart illustrating an example velocity profile of one or more elevator doors during a door opening cycle.

[0009] Figure 3 is a chart illustrating power consumed by a motor during the door opening cycle represented in Figure 2.

[0010] Figure 4 is a chart illustrating capacitance of an example capacitor bank during the door opening cycle represented in Figures 2 - 3.

[0011] Figure 5 is a schematic view of an example drive that includes an example pulse width modulator for providing a signal to an example DC motor configured to open and close one or more elevator doors.

[0012] Figure 6 is a schematic view of an example drive connected to a cabin-wide DC bus.

Detailed Description

[0013] The following description of example methods and apparatuses is not intended to limit the scope of the disclosure to the precise form or forms detailed herein. Instead the following disclosure is intended to be illustrative so that others may follow its teachings. [0014] Referring now to Figure 1, an example elevator door operator 100 is shown schematically. The elevator door operator 100 shown in the example of Figure 1 may generally include a power source 102, a motor 104, and a drive 106. The motor 104 may be configured to open and/or close one or more elevator doors of an elevator cab and/or hall doors of different levels of a building. In some examples, the motor 104 may be an induction motor or a

Permanent Magnet Synchronous Motor (PMSM). The power source 102 may represent, for instance, an electrical grid or a power feeder cable that supplies power from the electrical grid, an elevator control system, or the like. In many cases, the power source 102 supplies single- phase or three-phase alternating current (AC) power to the drive 106. The power source need not be considered part of the elevator door operator 100 in all instances.

[0015] With continued reference to Figure 1, the drive 106 may in some examples comprise a rectifier 108, a power supply control switch 110, a direct current (DC) bus 112 having a capacitor bank 114, and an inverter 116. Those having ordinary skill in the art will appreciate that in many cases the example elevator door operator 100 and/or the drive 106 may utilize other components such as, for example, regenerative resistors, regenerative control circuitry, bus voltage sensors, door speed control circuitry, elevator control circuitry, input isolation, transformers, DC chokes, fuses, circuit breakers, reactors, and/or input and output filters. What's more, the drive 106 may generate an AC signal for the motor 104 in some examples. In other examples, though, the drive 106 may generate a DC signal for the motor 104, as disclosed below.

[0016] As also explained below, the drive 106 may permit the flow of power from the motor 104 back to the capacitor bank 114. One example type of variable voltage variable frequency (VVVF) drive that permits this type of power regeneration is a current source inversion (CSI) drive. CSI WW drives offer advantages such as a clear current waveform and relatively simple circuitry.

[0017] Moreover, the example rectifier 108 of Figure 1 may convert a three-phase AC voltage from the power source 102 to a DC voltage. For instance, the rectifier 108 may convert three- phase 60 or 50 Hz power from a standard 220V, 440V, or higher utility supply line to a fixed or adjustable DC voltage. To convert the AC voltage, the rectifier 108 may comprise one or more silicon-controlled rectifiers (SCRs), gate commutated thyristors (GCTs), and/or symmetrical gate commutated thyristors (SGCTs), for example and without limitation. Although motors that open and close elevator doors are typically not high voltage systems, the drive 106 may include one or more transformers if there is a need for high voltage.

[0018] The DC voltage from the rectifier 108 may then be applied to the DC bus 112 that includes the capacitor bank 114. One function of the capacitor bank 114 is to eliminate or at least reduce any residual AC component from the DC voltage from the rectifier 108. The residual AC component is often referred to as voltage or current ripple. The DC bus 112 may in some cases also include one or more inductors to help regulate current ripple. Filtering current ripple helps provide a smoother DC signal to the inverter 116. In addition, the DC bus 112 can generally help isolate the inverter 116 and the motor 104 from the power source 102, which can be desirable in the event of a power surge or other disruption. It should be understood that in some cases other energy storage devices such as, for instance, batteries may be used in combination with or as alternatives to the capacitors.

[0019] Nonetheless, the DC bus 112 may transmit the DC voltage to the inverter 116. In general, the inverter 116 may convert the DC voltage into a variable voltage variable frequency signal to be supplied to the motor 104. By varying the voltage and frequency of the signal provided to the motor 104, the drive 106 can adjust the torque and speed of the motor 104.

Variable speed motor drives are typically more efficient than other control methods involving valves, turbines, hydraulic transmissions, dampers, and the like. That said, the inverter 116 may comprise power electronic switches such as, for example, insulated-gate bipolar transistors (IGBTs), SCRs, GTOs, or SGCTs, which may be switched on and off in sequence to generate a pulse width modulated (PWM) output signal for the motor 104. The PWM output signal may comprise a series of short-width pulses with constant amplitude. In that vein, an output voltage of the inverter 116 may be controlled by changing the gain of the inverter 116.

[0020] According to some example methods of operation, when an elevator cabin arrives at a level of a building, the elevator door operator 100 will open one or more elevator doors and, in many cases, one or more hall doors of the level of the building. When the elevator door operator 100 begins to open the doors, the motor 104 draws AC voltage from the drive 106 as the power source 102 and the capacitor bank 114 both contribute to powering the motor 104. Once the doors begin moving, the power supply control switch 110 may be opened so as to disconnect the power source 102. The capacitor bank 114 may supply the remainder of the power necessary for the motor 104 to accelerate and generally open the elevator doors. In many cases the capacitor bank 114 may be configured to provide a majority or even all of the power required, relative to the power source 102, to open and close the elevator doors. To that end, the capacitor bank 1 14 may be sufficiently large to provide the high currents necessary for rapidly accelerating doors to their maximum speed. Those having ordinary skill in the art will understand that speeds at which the elevator doors are opened and closed may be limited by horsepower of the motor 104 and capacity of the drive 106 that controls the motor 104. [0021] Once the doors are almost fully opened, the example elevator door operator 100 may use a form of dynamic braking to decelerate the elevator doors. Kinetic energy of the elevator doors, the motor 104, and other driven mechanisms is converted into potential energy stored in the capacitor bank 114 of the DC bus 112. More specifically, the motor 104 may become a generator as the elevator doors, the motor 104, and the other driven mechanisms apply a negative torque to a shaft of the motor 104, inverting the polarity of the voltage across the DC bus 112. By disconnecting the power source 102 before or as the elevator doors begin moving, the power supply control switch 110 causes the capacitor bank 114 to discharge, which consequently, ensures a sufficient amount of storage capacity in the capacitor bank 114 for receiving the potential energy harnessed by the motor 104 as the doors decelerate.

[0022] As shown in Figure 2, a velocity profile 150 of a door opening cycle illustrates how in some examples the elevator door operator 100 accelerates one or more elevator doors to a constant speed before decelerating the elevator doors. Figure 3 illustrates power consumption by the motor 104 to achieve the velocity profile shown in Figure 2. As those having ordinary skill in the art will recognize, the motor 104 consumes significantly less power after the elevator doors are accelerated to a constant speed. The power required by the motor 104 to maintain the elevator doors at a constant speed, however brief, is required mostly to overcome losses due to friction. As the elevator doors decelerate, the motor 104 acts as a generator and harnesses potential energy that is stored in the capacitor bank 114 as explained above. In particular, an area 160 above a power curve 162 and below an x-axis 164 represents an amount of energy that is harnessed and stored in the capacitor bank 114 during elevator door deceleration. By contrast, an area 166 above the x-axis 164 and below power curve 162 represents an amount of energy that is consumed by the motor 104 during door acceleration. [0023] Still further, Figure 4 illustrates capacitance of the capacitor bank 114 of the drive 106 for the same door opening cycle represented in Figures 2 - 3. In particular, a curve 170 representing the capacitance of the capacitor bank 114 indicates a starting capacitance 172 as the door opening cycle begins. As the motor 104 begins accelerating the elevator doors, the capacitance of the capacitor bank 114 is quickly diminished. The draw of power from the capacitor bank 114 slows as the elevators doors reach a constant speed. The capacitance of the capacitor bank 114 then reaches a low capacitance 174, but begins regaining capacitance as the elevator doors begin decelerating and the motor 104 begins converting the kinetic energy of the elevator doors into potential energy stored in the capacitor bank 114. At the end of the door opening cycle, the capacitance of the capacitor bank 114 reaches an ending capacitance 176.

[0024] If the capacitor bank 114 is not sufficiently recharged to support closure of the elevator doors, the power supply control switch 110 may be closed while the elevator doors are open so that the power source 102 is reconnected and can recharge the capacitor bank 114 from the ending capacitance 176 back to the starting capacitance 172. As shown in Figure 4, the power source 102 may recharge the capacitor bank 114 by approximately an amount of lost power 178 that was not or could not be harnessed. One of the primary reasons that the power source 102 may need to recharge the capacitor bank 114 is due to frictional losses, electrical losses, and other inherent inefficiencies.

[0025] Notwithstanding, a similar process may then occur as the elevator doors are closed. That is, the power source 102 and the capacitor bank 114 may both initially provide power to the motor 104 as the motor 104 begins to close the elevator doors. Before or as the doors start moving, the power supply control switch 110 may be opened so as to disconnect the power source 102 from the drive 106. The capacitor bank 114 may provide the remainder of the power necessary for the motor 104 to accelerate and generally close the elevator doors. Once the doors are almost fully closed, the elevator door operator 100 may again use dynamic braking to decelerate the elevator doors. As explained above, the motor 104 may act as a generator to recharge the capacitor bank 114 of the DC bus 112. After the elevator doors are fully closed and the elevator cabin begins traveling to another level, the power source 102 may be reconnected to further recharge the capacitor bank 114 if necessary.

[0026] In contrast with the example velocity profile 150 of the door opening cycle shown in Figure 2, it should be understood that speeds at which the elevator doors are closed may be constrained by the kinetic energy limit of the elevator door system. For example, the kinetic energy limit, which may be 8 Joules in some cases, may exist to protect passengers who might be impacted by the closing elevator doors. As a result, the speed at which elevator doors close may be less than the speed at which the elevator doors open, as the risk of pinching someone between elevator doors is not present during door opening cycles. Likewise, charts comparable to those shown in Figures 3 - 4 for door closing cycles would also have slightly different profiles.

[0027] Further, the power supply control switch 110 may remain open during deceleration of the elevator doors to prevent harnessed power from passing to the power source 102. Known regenerative braking drives and motors for elevators do not employ such switches. Rather, known regenerative braking drives and motors for elevators route at least a portion of harnessed power back to a power source such as an electrical grid, typically via power feeders, as described more fully in U.S. Patent No. 7,246,686 entitled "Power Supply for Elevator Systems Having Variable Speed Drives," which is incorporated by reference herein in its entirety. By dedicating all of the harnessed power to recharging the capacitor bank 114 in some examples here, the instantaneous peak power requirement from the power source 102 is considerably reduced because substantially more power can be supplied by the capacitor bank 114. One example consequence of such an arrangement allows for the use of smaller power feeders tethered to the elevator cabin as the peak power requirement from the power source 102 is considerably reduced. Further, the quantity of capacitors in a drive is typically defined by the requirement to filter ripple currents. But if additional capacitors are included in the capacitor bank 114 of the DC bus 112, more DC power can be stored, which permits the elevator door operator 100 to accelerate the elevator doors to limiting speeds more quickly. Likewise, more DC power stored in the capacitor bank 114 also reduces instantaneous peak power required from the power source 102.

[0028] Those having ordinary skill in the art will appreciate that in some examples, the power source 102 may not necessarily be used in combination with the capacitor bank 114 to begin opening or begin closing the doors. In such cases, the capacitor bank 114 in the drive 106 may be large enough to power the motor 104 on its own, without the assistance of the power source 102. Accordingly, the power source 102 may simply be used to account for lost power and supplement the motor 104 in recharging the capacitor bank 114. In such examples, the power source 102 may be disconnected before the motor 104 begins accelerating the doors.

[0029] Those having ordinary skill in the art will recognize that the present disclosure is not in any way limited to elevator door operators that employ AC motors. For instance, the example elevator door operator 100 shown in Figure 5 includes a DC motor 190 connected to a pulse width modulator 192 of the drive 106. In still other examples that utilize a DC motor, an inverter may be configured to produce a variable voltage direct current.

[0030] Figure 6 illustrates still another example wherein the example drive 106 is connected to a cabin-wide DC bus 210 instead of the power source 102. The cabin-wide DC bus 210 may be used for other electrical needs of an elevator cabin. For example, the cabin-wide DC bus 210 may be used not only to selectively power the motor 104 and recharge the capacitor bank 114, but also to power lights, push-buttons, signals, and other electronic devices present on the elevator cabin. Similarly, the cabin-wide DC bus 210 may in some examples provide power to multiple motors, not just the motors 104, 190 shown in Figures 1 and 5, respectively.

[0031] The cabin-wide DC bus 210 may be connected to an electrical grid, but the cabin-wide DC bus 210 may also receive power from other sources. One example source includes power generated by an elevator braking system 212, as disclosed in incorporated U.S. Patent No. 7,246,686. Another example source includes power generated by a vibration dampening device 214 that dampens vibrations within the ropes of an elevator car and converts such vibrations into electrical energy, as disclosed more fully in U.S. Patent Publication No. 2015/0360909 entitled "Elevator Dampener and Energy Harvesting Device and Method," which is incorporated by reference herein in its entirety.

[0032] Although certain example methods and apparatus have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus, and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.