ELEVATOR

Abstract

The invention relates to an elevator comprising at least one elevator car moved by at least one elevator motor, which elevator motor is driven by a frequency converter controlled by a control device of the elevator, the frequency converter comprising a rectifier bridge, an inverter bridge and a DC link connected in-between, the inverter bridge being connected to the elevator motor and the rectifier bridge being connected to AC mains via three phase supply lines comprising an LCL-filter and a mains switch. The elevator further comprises a backup power supply and a safety device of the control device, which in case of a mains power failure is configured to switch off the mains switch and to connect the backup power supply to the DC link and/or to at least one phase supply line, whereby the rectifier bridge is a bidirectional rectifier bridge being configured to convert DC supplied to the DC link from the backup power supply to an AC voltage supplied to at least two of the phase supply lines connected with at least one load circuit. An earth fault protection circuit for the load circuit is connected between earth and a common terminal of the capacitors of the LCL filter for monitoring an earth fault indicating signal, and which earth fault protection circuit is configured to issue an earth fault signal and/or initiating earth fault safety measures, dependent on the earth fault indicating signal.

Claims

1. Elevator comprising at least one elevator car moved by at least one elevator motor, which elevator motor is driven by a frequency converter controlled by a control device of the elevator, the frequency converter comprising a rectifier bridge, an inverter bridge and a DC link connected in-between, the inverter bridge being connected to the elevator motor and the rectifier bridge being connected to AC mains via three phase supply lines comprising an LCL-filter and a mains switch, which elevator further comprises a backup power supply and a safety device of the control device, which in case of a mains power failure is configured to switch off the mains switch and to connect the backup power supply to the DC link and/or to at least one phase supply line, whereby the rectifier bridge is a bidirectional rectifier bridge being configured to convert DC supplied to the DC link from the backup power supply to an AC voltage supplied to at least two of the phase supply lines connected with at least one load circuit, whereby an earth fault protection circuit for the load circuit is connected between earth and a common terminal of the capacitors of the LCL filter for monitoring an earth fault indicating signal, and which earth fault protection circuit is configured to issue an earth fault signal and/or initiating earth fault safety measures, dependent on the earth fault indicating signal.

2. Elevator according to claim 1, wherein mains switch is operated by a safety device of the elevator, which safety device also connects the backup power supply to the DC link.

3. Elevator according to claim 1, wherein the backup power supply is connected in parallel with a series-connected rectifier bridge and inductor of the phase supply line, so that the negative terminal of the backup power supply is connected to the DC link and its positive terminal is connected to the phase supply line.

4. Elevator according to claim 2, wherein the output of the earth fault protection circuit is connected to an input of the safety device of the elevator.

5. Elevator according to claim 1, wherein a position sensor for the elevator car is connected to the safety device.

6. Elevator according to claim 1, wherein the load circuit is connected to the phase supply lines without the intermediation of a galvanically isolating transformer.

7. Elevator according to claim 1, wherein the load circuit is connected to the phase supply lines via an interrupting switch controlled by the safety device.

8. Elevator according to claim 1, wherein the earth fault indicating signal is a current or voltage signal.

9. Elevator according to claim 1, wherein the earth fault protection circuit comprises an op-amplifier.

10. Elevator according to claim 1, wherein the safety device is connected to the control device, which is configured upon receipt of the earth fault signal to drive the car in travelling direction to the next door zone and then to de-activate the elevator.

11. Elevator according to claim 1, wherein the earth fault protection circuit comprises a comparator which is configured to compare the earth fault indicating signal with a threshold value, and to issue an earth fault signal when the threshold value is exceeded.

12. Method for operating an elevator in case of a mains power failure, in which method an elevator is used having at least one elevator car moved by at least one elevator motor, which elevator motor is driven by a frequency converter controlled by a control device of the elevator, the frequency converter comprising a bidirectional rectifier bridge, an inverter bridge and a DC link connected in-between, the inverter bridge being connected to the elevator motor and the rectifier bridge being connected to AC mains via three phase supply lines comprising an LCL-filter and a mains switch, whereby the elevator further comprises a backup power supply and a safety device of the control device, which in case of a mains power failure switches off the mains switch and connects the backup power supply to the DC link and/or to a phase supply line, and the rectifier bridge converts the DC supplied to the DC link from the backup power supply to an AC voltage supplied to at least two of the phase supply lines, to which at least two supply lines at least one load circuit is connected, whereby an earth fault protection is provided by monitoring an earth fault indicating signal between earth and a common terminal of the capacitors of at least two phases of the LCL filter, and by issuing an earth fault signal and/or initiating earth fault safety measures, depending on the earth fault indicating signal.

13. Method according to claim 12, wherein the safety measures comprise the drive of the elevator car to the next door zone in traveling direction.

14. Method according to claim 12, wherein the safety measures comprise de-activation of the elevator car after the car has stopped or stands in a door zone of the elevator.

15. Method according to claim 12, wherein the safety measures comprise indicating a load circuit earth fault to a maintenance remote centre.

Description

[0029] The invention is now described via a preferred schematic example in connection with the enclosed drawing.

[0030] FIG. 1 shows a schematic diagram of a first embodiment of an elevator in connection with the earth fault protection for the motor drive of an elevator, whereby the backup power supply is connected with the DC link, and

[0031] FIG. 2 shows a schematic diagram of a second embodiment of an elevator in connection with the earth fault protection for the motor drive of an elevator, whereby the backup power supply is connected with the DC link and with a supply line.

[0032] FIG. 1 shows the electric and electronic parts of an elevator 10 comprising a frequency converter 12 driving an elevator motor 14. The frequency converter 12 comprises a rectifier bridge 16, an inverter bridge 18 and a DC link 20 located in between. The inverter bridge 18 is connected to the motor 14 and the rectifier bridge 16 is connected to three phase supply lines 22a, 22b, 22c which comprise an LCL filter 24 as well as a mains switch 26 and are connected with the AC phases L1, L2, L3 of a public AC electricity network.

[0033] The elevator motor 14 comprises two elevator brakes 28a, 28b which are controlled by a control device 30 of the elevator 10 having an integrated safety device 32 which may also be separate from the control device. The control device 30 is connected with a tachometer 34 enabling the control device 30 to obtain a signal regarding the speed of the elevator motor as well as with a position sensor 36 informing the control device and of course the safety device 32 of the position of the elevator car in the shaft, or whether the car has reached a door zone (door zone sensor). The control device 30 controls the inverter bridge 18 as well as the rectifier bridge 16 via control lines. The control device 30 also controls a backup power supply 38 which preferably comprises a battery and/or a supercapacitor or the like. Also the backup power supply 38 is controlled by the control device 30 or by the safety device 32, respectively. At least one load circuit 40, for example any kind of elevator electrification and/or preferably a door operator of the elevator car, is connected to two of the phase supply lines 22a, 22b via an interruption switch 42 which is controlled by the safety device 32. Also the mains switch 26 is controlled by the safety device 32.

[0034] The LCL filter 24 comprises first and second impedances 44a-c, 46a-c, e.g. coils as well as capacitors 48a-c which have a common terminal 49 which is connected to a first input 51a of an op-amplifier 52 which are forming parts of an earth fault detection circuit 50. The second input 51b is connected to earth. The output of the op-amplifier is connected to a transmission node 54 which may be an opto-coupler, a wireless transmitter or a cable, whereby the corresponding receiving part to the transmission node 54 is a receiver node 56 connected with the control device or the safety device 32, respectively. The control device 30 is also connected with a safety chain 58 so that the control device 30 of the elevator 10 also gets other safety-related information from the motor, from the elevator shaft, from the landing doors and the car doors and from all other safety-relevant parts of the elevator.

[0035] The elevator works as follows: In case of a mains power off, the safety device 32 immediately controls the mains switch 26 to open and the interruption switch 42 to close and simultaneously it controls the backup power supply 38 to be connected with the DC link 20 via a connecting switch 39. Simultaneously, the rectifier bridge 16 is controlled to produce an alternating current, preferably 230 V AC, in two phase supply lines 22a, 22b to which also the at least one load circuit 40 is connected via the now closed interruption switch 42. Via this solution, the load circuit, for example the door operator of the elevator car, can still be kept working so that the car doors may be opened when the elevator car reaches a landing. The earth fault protection circuit 50 is provided to detect an earth fault in the arrangement of the load circuit 40 and is coupled thereto via its first input terminal 51a and the common terminal 49 of the capacitors 48a-c of the LCL circuit 24. The other input terminal 51b is connected to earth. On this behalf, an earth fault indication signal between the op-amplifier inputs 51a and 51b of the earth fault detection circuit 50 is monitored and if there is an earth fault in the load circuit 40, this leads to a signal between the two input terminals 51a, 51b of the op-amplifier 52. The output of the op-amplifier 52 is connected to the transmission node 54 which informs the safety device 32 as well as the control device 30 that an earth fault is present in the load circuit 40. The safety device 32 is then able to take the necessary measures to bring the elevator to a safe stop as an earth fault in the load circuit is not a severe fault. Preferably, in this case, the safety device 32 indicates the earth fault to the control device which then controls the elevator motor to drive the elevator car to the next landing door in the current driving direction whereby the car speed is monitored via the tachometer 34 and the arrival of the elevator car at landing zone or door zone is monitored via the position sensor 36. After the car has arrived the door zone, the control device 30 stops the motor and de-energizes the brakes 28 with the energy of the backup power supply 38 which is connected to the DC link 20. In this connection it is to be mentioned that preferably also the brake drive for the elevator brakes 28a and 28b is connected to the DC link. Thus, with the present invention, an economical solution is provided for handling earth faults in at least one load circuit in a mains power off situation of the elevator.

[0036] In FIG. 1 the backup power supply is connected only to the DC link. The embodiment of FIG. 2 is nearly identical to FIG. 1 so that identical or functionally similar components are designated with the same reference numbers. In FIG. 2in contrast to the embodiment of FIG. 1the backup power supply is connected in parallel with the series-connected rectifier bridge 16 and the first impedance 44a,b,c of the phase supply line 22a,b,c. Hence, the negative terminal of the backup power supply 38 is connected to the DC link 20 and its positive terminal is connected to one of the phase supply lines 22a, 22b or 22c, so that the negative terminal is all the time connected to the negative branch of the DC link and the positive terminal is connectable with a controllable switch to one phase supply line 22a, 22b, 22c of the mains L1, L2, L3. Particularly in this case the positive terminal is connected such that an a first impedance 44a, 44b, 44c is connected between the rectifier bridge 16 and the connection point of the positive terminal to the phase supply line 22a, 22b, 22c. Hence, the series-connected impedance 44a, 44b, 44c and rectifier bridge 16 may be used as a boost converter to boost backup battery voltage to the DC link voltage level. The load is in this case connected to the other two phase supply lines 22a, 22b, 22c. Hence, the rectifier bridge 16 may boost a backup battery supply 36 while simultaneously converting the DC link voltage into AC for the load connected with the at least two supply lines 22a, 22b, 22c.

[0037] It is clear for the skilled person that the invention is not restricted to the disclosed embodiment but that the invention may deviate within the scope of the appended patent claims.

LIST OF REFERENCE NUMBERS

[0038] 10 elevator [0039] 12 frequency converter [0040] 14 elevator motor [0041] 16 rectifier bridge [0042] 18 inverter bridge [0043] 20 DC link [0044] 22a,b,c phase supply lines [0045] 24 LCL filter [0046] 26 mains switchcontactor relay [0047] 28a,b elevator brakes [0048] 30 control device [0049] 32 safety device [0050] 34 tachometerspeed sensor [0051] 36 position sensor of the elevator car [0052] 38 backup power supply [0053] 40 load circuit (door circuit, lightning, ventilation etc.) [0054] 42 interruption switch [0055] 44a,b,c first impedances of the LCL filterfirst coils [0056] 46a,b,c second impedances of the LCL filtersecond coils [0057] 48a,b,c capacitors of the LCL filter [0058] 49 common terminal of the capacitors of the LCL filter [0059] 50 earth fault detection circuit [0060] 51a,b input terminals of the op-amplifier [0061] 52 op-amplifier [0062] 54 transmission node [0063] 56 receiver node [0064] 58 safety chainsafety circuit of the elevator