Method for performing a manual drive in an elevator after mains power-off

Abstract

In a method for performing a manual drive in an elevator after mains power-off, the frequency converter of the motor is separated from mains, any safety blocking of the brake drive and/or motor drive is disabled, current is supplied from the battery to the brake drive to open the elevator brake and current is supplied from the battery to the drive control to allow regulation of the motor speed via the inverter bridge, the manual drive control observes the motor speed via the speed sensor and starts a speed feedback loop to regulate the motor speed to a manual drive reference value by feeding a three phase-AC current to the motor windings via the semiconductors of the inverter bridge, which manual drive speed reference is lower than the speed reference for normal elevator operation, when the car reaches a floor level the floor level indicator is activated, and the actuator is released whereafter the current supply from the battery to the elevator brake is interrupted and the previous disabled safety blocking of the brake drive and/or motor drive is enabled again.

Claims

1. A method for performing a manual drive in an elevator after mains power-off, the elevator comprising: an AC elevator motor; a motor drive having a frequency converter, whereby the frequency converter comprises a rectifier bridge and an inverter bridge with semiconductor switches, rectifier bridge and the inverter bridge being connected via a DC link, and whereby the motor drive comprises a drive control at least to control the semiconductor switches of the inverter bridge to regulate the speed of the elevator motor to a reference speed; at least one elevator brake located in connection with the elevator motor and/or with a traction sheave of the motor; at least one elevator car running in an elevator driveway; at least two landing floors connected with the elevator driveway; at least one speed sensor for the motor speed and/or car speed; and a manual emergency drive connected to the drive control and comprising a manual drive control, a back-up battery and a manual operating interface with at least one actuator as well as a floor level indicator, the manual operating interface being disposed in a control panel of the elevator, in which method, upon actuating the actuator, the following steps are carried out: a) separating the frequency converter of the motor from mains; b) disabling any safety blocking of the brake drive and/or motor drive; c) supplying current from the battery to the brake drive to open the elevator brake and supplying current from the battery to the drive control to allow regulation of the motor speed via the inverter bridge; d) the manual drive control observing the motor speed via the speed sensor and starting a speed feedback loop to regulate the motor speed to a manual drive reference value by feeding a three phase-AC current to the motor windings via the semiconductors of the inverter bridge, the manual drive speed reference being lower than the speed reference for normal elevator operation; e) when the car reaches a floor level activating the floor level indicator; and f) releasing the actuator, whereafter interrupting the current supply from the battery to the elevator brake and enabling the previous disabled safety blocking of the brake drive and/or motor drive again.

2. The method according to claim 1, wherein in step e) the current supply from the battery to the motor drive is interrupted after the current supply from the battery to the elevator brake is interrupted.

3. The method according to claim 2, wherein in step b) the at least one safety signal of any safety devices of the elevator is bypassed or altered to enable operation of the inverter bridge and of the elevator brake, and in step f) said bypassing is stopped.

4. The method according to claim 2, wherein additionally to the actuator a mode select switch is provided which must first be turned to set the elevator to a rescue operation mode allowing steps a) to f).

5. The method according to claim 1, wherein in step b) the at least one safety signal of any safety devices of the elevator is bypassed or altered to enable operation of the inverter bridge and of the elevator brake, and in step f) said bypassing is stopped.

6. The method, according to claim 5, wherein the safety functions are bypassed manually via the actuator or via a different operating element located in the manual operating interface.

7. The method according to claim 1, wherein additionally to the actuator a mode select switch is provided which must first be turned to set the elevator to a rescue operation mode allowing steps a) to f).

8. The method according to claim 1, wherein the actuator must be continuously pushed to allow steps a) to f) or c) to f) to be performed, whereby any release of the actuator immediately leads to step f).

9. The method according to claim 1, wherein in step a) the frequency converter of the motor drive is separated from mains with a manual main switch or via a separate main relay, installed between the mains and the rectifier bridge of the frequency converter.

10. The method according to claim 1, wherein the manual drive reference value in step d) is chosen to keep the car speed to 0.3 m/s at the maximum.

11. The method according to claim 1, wherein step f) is performed automatically when step e) happens to take place.

12. The method according to claim 1, wherein the control principle of the speed regulation in step d) is a vector control with speed control and motor current control loops.

13. The method according to claim 1, wherein the manual operating interface comprises a mode select switch, which sets the elevator in an emergency drive mode in which steps a), b) and eventually c) are performed.

14. An elevator comprising: an AC elevator motor; a motor drive to regulate the speed of the elevator motor with a frequency converter, whereby the frequency converter of the motor drive comprises a rectifier bridge and an inverter bridge with semiconductor switches, the rectifier bridge and the inverter bridge being connected via a DC link, and whereby the motor drive comprises a drive control at least to control the semiconductor switches of the inverter bridge to regulate the elevator motor to a reference speed; an elevator brake located in connection with the elevator motor and/or with a traction sheave of the motor; at least one elevator car running in an elevator driveway; at least two landing floors connected with the elevator driveway; at least one speed sensor for the motor speed and/or car speed; a manual emergency drive comprising a manual drive control, a back-up battery and a manual operating interface with at least one actuator as well as a floor level indicator, the manual operating interface being disposed in a control panel of the elevator; and a switch or relay to separate the frequency converter of the motor from mains, wherein the manual drive control is connected to a connecting relay which is provided to connect the battery with the brake drive and with the DC link of the frequency converter and with the drive control to allow regulation of the motor speed via the inverter bridge, wherein the manual drive control is connected to a safety activation circuit, enabling the brake drive and the motor drive to issue signals during the manual drive operation, and the drive control is configured during the manual drive to obtain the motor speed via the speed sensor, and to start a speed feedback loop to regulate the motor speed to a manual drive reference value by feeding a three phase-AC current to the motor windings via the semiconductors of the inverter bridge, the manual drive speed reference being lower than the speed reference for normal elevator operation.

15. The elevator according to claim 14, wherein the manual drive control is configured to disconnect the battery from the elevator brake and/or from the motor drive and drive control when the floor level indicator is activated.

16. The elevator according to claim 14, wherein the actuator is a push button.

17. The elevator according to claim 14, wherein the control panel is located in a landing door frame.

18. The elevator according to claim 14, wherein the manual drive control is configured to bypass or alter a safety signal for the brake drive and drive control.

19. The elevator according to claim 14, wherein the manual operating interface comprises a mode switch, which initiates the manual emergency device to bypass safety signals safety devices which block the brake drive and/or motor drive from issuing control impulses.

20. The elevator according to claim 14, wherein a DC converter is connected in the DC link between the connection of the battery to the DC link and the inverter bridge or the connection of the battery to the frequency converter is connected to the AC side of the rectifier bridge and the rectifier bridge is of the regenerating type.

Description

(1) The FIGURE is a schematic view of a part of the elevator involved in an emergency drive after mains power off.

(2) The invention is described hereinafter via an example in connection with the appended drawing. This shows a part of an elevator which is involved in a manual emergency drive of the elevator after mains power off. The elevator 10 comprises a motor drive 12 driving an elevator motor 14 and a brake drive 16, actuating two elevator brakes 18. The motor drive 12 comprises a frequency converter 20 with a rectifier bridge 22, an intermediate DC link 24 and an inverter bridge 26 which is connected to the elevator motor 14. In the DC link 24 a DC converter 25 is located between the rectifier bridge 22 and the inverter bridge 26 to boost the DC voltage to a level high enough for the inverter bridge 26 to work. On the high level side of the DC converter 25 an optional smoothing capacitor 27 is connected to reduce any voltage ripple in the DC link 24 at the input of the inverter bridge 26. At least the inverter bridge 26 of the frequency converter 20 is controlled by a drive control 28. The motor drive 12 further comprises a mains relay 30 which can be activated via a manual drive control 32 of the manual emergency drive which is connected to the drive control 28 or integrated with it. A tachometer 34 sensing the rotational speed of the elevator motor 14 is connected to the drive control 28. Furthermore, the drive control 28 is connected with a control panel 36 of the elevator 10 comprising a display 38, an operating panel 40 as well as a manual operating interface 42 comprising an actuator 44 preferably embodied as a push button, a manual rescue switch 46 as well as floor level indicator 48 indicating when the elevator car has reached a floor level of the elevator. The signals from the drive control 28 to the inverter bridge 26 are guided over a pulse blocking device 50 which is triggered by a safety signal line 52 for example from a safety device (safety module with safety chain) of the elevator 10. In normal operation, this signal line 52 is for example on +24 V level allowing the brake drive 16 and the drive control 28 to issue their control commands to the respective components 18, 26. In case of power off of AC mains 54, this signal on the safety signal line 52 drops to 0 V whereafter the drive control 28 and the brake drive 16 cannot issue any control pulses. In the safety signal line 52, an OR member 56 is located which is connected to an output of the manual drive control 32. Furthermore, a connecting relay 58 is provided to connect a backup battery 60 via connection (or connection lines) 23 to the DC link 24 of the frequency converter and thus also to the drive control 28 as well as to the brake drive 16.

(3) Alternatively, instead of the connecting lines 23 the backup battery 60 could be connected to the frequency converter 20 via the AC side of the rectifier bridge 22, with the dotted alternative connection lines 21. This is possible if the rectified bridge 22 is of the regenerating type, including AC side inductors. This kind of rectified bridge 22 is capable of boosting the battery voltage to a higher DC link voltage sufficient for the inverter bridge 26 to work. In this case a DC converter 25 is necessarily needed in DC link 24.

(4) The operation of an emergency drive is as follows:

(5) After power off of AC mains 54, the elevator 10 automatically sets the voltage on the safety signal line 52 to zero disabling the issuing of control pulses of the drive control 28 and brake drive 16. In this case, the operator opens a cover door of the elevator control panel 36 and pushes the manual rescue switch 46 to manual drive mode. This activates mains relay 30 as to separate the frequency converter 20 from AC mains 54. Furthermore, the manual drive control 32 issues a 24 V signal to the OR member 56 so that the pulse blocking device 50 and safety device in the brake drive 16 is deactivated so that the brake drive 16 and the drive control 28 can issue control signals to their respective components. Now the actuator (manual drive push button) 44 is pushed which leads to the activation of the connecting relay 58 as to connect the backup battery 60 with the brake drive 16 as well as with the DC link 24 of the frequency converter 20 of the motor drive 12. First, brake drive 16 supplied current to electromagnets of the brakes 18 to open the brakes. The drive control 28 observes the motor speed via the tachometer 34 and the drive control 28 starts a feedback loop to regulate the motor speed to a manual drive reference value by feeding a three-phase AC current to the elevator motor via the semiconductors of the inverter bridge 26. This means that the elevator motor 14 is actively driven (active dynamic braking) by the inverter bridge as to rotate with a given manual drive speed reference which is lower than the nominal velocity of the elevator motor when driving the elevator car with nominal velocity. The manual drive speed reference for the elevator motor can for example be chosen so that the speed of the elevator car does not exceed a value of for example 0.3 m/s. When the car reaches a floor level which is sensed by the motor drive via a floor level sensor 62, the floor level indicator 48 is activated and either the manual drive control 32 automatically stops the elevator motor 14 for example by disabling the action of the actuator 44 or by overriding the action of the actuator by an own switching mechanism with which the current supply from the battery to the elevator brake is interrupted and preferably also the current supply to the motor drive is interrupted, for example by operating the connecting relay 58 as to separate the backup battery 60. Another possibility is that the actuator is released manually by the operator when he sees the floor level indicator lighting up so that the stopping of the elevator car is done manually by the operator. In both cases, the elevator is driven to the next landing door with a given manual drive reference velocity provided for an emergency drive which is lower than the nominal velocity.

(6) In some embodiments it is also possible that against the force conditions of the imbalance between car and counterweight, the car is operated in counter-direction to its normal moving direction due to gravitational force. Thus, it is possible to drive the elevator car to special landings which are intended for these emergency drives and for example to avoid certain landings as for example the top level or the base level. This of course requires that battery capacity is dimensioned adequately.

(7) In the above embodiment, there is a separate manual rescue switch and a separate actuator. Of course, there might only be the actuator so that the elevator automatically goes into the manual emergency drive mode when the actuator is pressed. Furthermore, for the bypassing of safety devices, a further push button may be located in the manual operating interface.

(8) When after the emergency drive the elevator is stopped and the battery is disconnected, preferably also the bypassing of the safety devices is stopped so that the signal on the safety signal line is 0 V again which disables the brake drive 16 and the drive control 28 from issuing any control signals to the respective components 26, 18.

(9) The invention is not restricted to the above-mentioned embodiment but may be varied within the scope of the appended patent claims.

LIST OF REFERENCE NUMBERS

(10) 10 elevator 12 motor drive 14 elevator motor 16 brake drive 18 elevator brakes 20 frequency converter 21 alternative connection of the battery to the AC side of the rectifier bridge of the frequency converter, in case of a rectifier bridge of the regenerating type 22 rectifier bridge 23 connection of the battery to the DC link in one embodiment of the invention 24 DC link 25 DC converter 26 inverter bridge with semiconductor switches (e.g. MOSFETs or IGBTs) 27 smoothing capacitor 28 drive control 30 mains relay 32 manual drive control 34 tachometer 36 elevator control panel 38 window or display 40 operating panel 42 manual operating interface 44 actuator 46 manual rescue switch 48 floor level indicator 50 pulse blocking device 52 safety signal line 54 AC mains 56 logical OR member 58 connecting relay 60 backup battery 62 floor level sensor