ELEVATOR

Abstract

The invention relates to an elevator comprising an elevator motor driving at least one elevator car in a hoisting path, which elevator motor is driven via a frequency converter controlled by a control device of the elevator. The frequency converter comprises a rectifier bridge and an inverter bridge and a DC link in-between. The elevator further comprises at least one elevator brake acting on a brake element rotating with the rotor of the elevator motor, which elevator brake is driven via a brake drive which is connected to the DC link of the frequency converter an comprises a DC/DC converter having its primary side connected to the DC link and its secondary side connected to a brake circuit comprising at least one brake coil of the elevator brake and at least one rectifying element. According to the invention in the primary side of the DC/DC converter a first semiconductor switch is connected which is controlled by the control device of the elevator. In the brake circuit a second semiconductor switch is connected which is also controlled by the control device of the elevator, whereby an earth fault indication circuit is connected between the brake circuit and earth. The earth fault indication circuit comprises an transmitting part of an opto-coupler, which opto-coupler has its sensor part connected to an earth fault transmission circuit connected to the control device of the elevator. The control device is configured to control the first and/or second semiconductor switch depending on the signal of the earth fault transmission circuit.

Claims

1. Elevator comprising an elevator motor driving at least one elevator car in a hoisting path, which elevator motor is driven via a frequency converter controlled by a control device of the elevator, the frequency converter comprising a rectifier bridge and an inverter bridge and a DC link in between, the elevator further comprises at least one elevator brake acting on a brake element rotating with the rotor of the elevator motor, which elevator brake is driven via a brake drive which is connected to the DC link of the frequency converter, whereby the brake drive comprises a galvanically separating link component having a primary side connected to the DC link and a secondary side connected to a brake circuit comprising at least one brake coil of the elevator brake and at least one rectifying element, whereby in the primary side of the link component a first semiconductor switch is connected which is controlled by the control device of the elevator, and whereby in the brake circuit a second semiconductor switch is connected which is also controlled by the control device of the elevator, whereby an earth fault indication circuit is connected between the brake circuit and earth, and which earth fault indication circuit comprises an transmitting part of an galvanically isolating transmission element, which transmission element has its receiving part connected to an earth fault transmission circuit connected to the control device of the elevator, wherein the control device is configured to control the first and/or second semiconductor switch depending on the signal of the earth fault transmission circuit.

2. Elevator according to claim 1, wherein the galvanically separating link component is a DC/DC converter.

3. Elevator according to claim 1, wherein the control device of the elevator is configured to switch on/off the first as well as the second semiconductor switch depending on the signal of the earth fault transmission circuit.

4. Elevator according to claim 1, wherein the galvanically isolating transmission element is an opto-coupler.

5. Elevator according to claim 4, wherein the transmitting part of the opto-coupler is a LED.

6. Elevator according to claim 1, wherein the earth fault indication circuit comprises a third diode in series with the transmitting part of the galvanically isolating transmission element.

7. Elevator according to claim 1, wherein the earth fault indication circuit comprises a resistor in series with the transmitting part of the galvanically isolating transmission element, which resistor has a higher resistance than the brake coil.

8. Elevator according to claim 7, wherein the resistance of the resistor of the earth fault indication circuit is at least ten times, preferably at least hundred times as high as the resistance of the brake coil.

9. Elevator according to claim 1, wherein the first semiconductor switch is PWM controlled.

10. Elevator according to claim 1, wherein a varistor is connected in parallel to the brake coil.

11. Elevator according to claim 10, wherein a second diode is connected in series with the varistor.

12. Elevator according to claim 1, wherein the rectifying element comprises a at least one diode and/or at least one smoothing capacitor.

13. Elevator according to claim 1, wherein the control device is connected with a location sensor of the elevator car in the shaft and the control device comprises a delay circuit which in case of an earth fault signal from the earth fault transmission circuit delays the switching off of the first and/or second semiconductor switch until the car has arrived or stopped at a door zone of the elevator.

14. Elevator according to claim 1, wherein the control device is configured to prevent a re-start of the elevator after having received an earth fault signal from the earth fault transmission circuit.

15. Method for operating an elevator in an earth fault condition of the brake circuit using an elevator according to claim 1, wherein after receiving an earth fault signal from the earth fault transmission circuit the control device drives the elevator car to the next landing.

16. Method according to claim 15, wherein after having driven the car to the landing a re-start of the car is prevented.

17. Method according to claim 15, wherein during a stop of the elevator car following steps are performed: First the first semiconductor switch is controlled to supply power to the secondary side of the DC/DC converter, e.g. by PWM control and the second semiconductor switch is controlled off, then, if the earth fault transmission circuit does not indicate an earth fault, the second semiconductor switch is controlled on, In case of the earth fault is detected, the first semiconductor switch is controlled off and the elevator is prevented to start. The primary use case is preferably just before the elevator travel or right after the travel when the elevator car is at landing zone.

18. Method according to claim 15, wherein during a movement of the elevator car following steps are performed: First the first semiconductor switch is controlled to supply power to the secondary side of the DC/DC converter, e.g. by PWM control, and the second semiconductor switch is controlled on, then the second semiconductor switch is switched off for a limited period, which is short enough not to engage the brake, the presence of an earth fault is monitored via the earth fault transmission circuit then the second semiconductor switch is switched back on irrespective of the presence of the earth fault before the brake engages and the elevator is controlled to travel to its destination.

Description

[0032] The invention is hereinafter described by way of an example in connection with the enclosed drawing. In this drawing, FIG. 1 shows a schematic diagram of an elevator having an earth fault detection in the brake circuit.

[0033] FIG. 1 shows the schematic diagram of a brake drive 11 of the elevator brake, which brake drive 11 is connected to the two terminals DC+, DC of a DC link which is part of a frequency converter of an elevator motor drive, whereby the DC link is provided between a rectifier bridge and an inverter bridge. The rectifier bridge is connected with AC mains and the inverter bridge is connected with the elevator motor, eventually via switches or contactors.

[0034] According to the invention, the brake drive 11 comprises a DC/DC converter 10 which is connected via a first semiconductor switch Q1 of the brake drive with the terminals DC+, DC of the DC link. The secondary side of the DC/DC converter 10 forms part of a brake circuit 20 of the brake drive 11. The secondary part of the DC/DC converter 10 is thus connected to a brake coil 12 of the elevator brake via a rectifying diode 14 and a second semiconductor switch Q2. Parallel to the brake coil 12, a smoothing capacitor 16 as well as varistor 18 in series with a second diode 19 is connected, whereby the smoothing capacitor 16 reduces the DC voltage ripple in the brake circuit 20 which is formed by all the above-mentioned components connected with the secondary side of the DC/DC converter 10. The varistor 18 is used for clamping the brake coil voltage and dropping the brake faster in case transistor Q2 is opened. In normal stops, DC/DC converter is switched off and Q2 is kept closed for short period to allow inductive current to decay through the transformer secondary. This causes brake coil current to freewheel causing slow and noiseless dropping of the brake pads. Furthermore, an earth fault indicator circuit 22 is connected between the brake circuit 20 and earth whereby the earth fault indicator circuit comprises an LED 24 as the transmitting part of an opto-coupler 26 in series with a resistor 23. The resistor has a resistance higher than that of the brake coil 12, preferably at least by a factor 10, preferably at least by a factor 100, so that the value is preferably in a range of 1 k to 500 k. Thus, the brake circuit is sufficiently isolated against earth. The receiving or sensing part 28 of the opto-coupler 26 forms an earth fault transmission circuit 27, which is connected to the control device 40. The control device 40 may be or may comprise or maybe connected to a safety device 30 of the elevator. The control device 40 is further connected to the control gates of both semiconductor switches Q1 and Q2 which semiconductor switches may preferably be transistors. The control device 40 is further connected with a location sensor 32 of the elevator car, for example a door zone sensor, so that the control device 40 or safety device 30 gets information when an elevator car arrives or stops in a door zone. The invention works as follows:

[0035] In case the brake circuit 20 has an earth fault which is indicated by the broken lines 34a, 34b, and the semiconductor switch Q2 is controlled off (not to conduct), this immediately leads to a current flow in the earth fault indication circuit 22 which leads to an emission of the LED 24 of the opto-coupler 26. Via the receiving part 28 of the opto-coupler 26, the control or safety device activates a delay circuit 36 which is connected to the input of the location sensor and of the earth fault transmission circuit in a kind of AND link so that only when also the location sensor indicates that the elevator car has stopped, is stopping or has arrived at a door zone, the safety device 30 or control device 40 is allowed to shut down the first semiconductor switch Q1 and/or the second semiconductor switch Q2. Preferably, the control device 40/safety device 30 has a succession circuit 38 which leads in case of the shutting down of the brake circuit first to the shutting down of the first semiconductor switch Q1 and only afterwards of the second semiconductor switch Q2. This leads to the shutting down of the DC/DC converter in such a way that the brake is engaged/gripped slowly and silently.

[0036] The presence of an earth fault in the brake circuit 20 can be monitored before an elevator travel by controlling the first semiconductor switch Q1 to power the brake circuit 20 while the second semiconductor switch Q2 is off. In another embodiment, the presence of an earth fault can be monitored after an elevator travel by controlling the second semiconductor switch Q2 off while still powering the brake circuit 20 by controlling the first semiconductor switch Q1. Also, in another embodiment the presence of an earth fault can be monitored during the elevator travel by controlling the second semiconductor switch Q2 off and then back on. The period when the second semiconductor switch Q2 is off is less than the time required for the brake to engage/grip, preferably less than 50 milliseconds. (This depends on the inertia/mass of the brake system.) Hence, this can be performed during the elevator travel.

[0037] The invention thus allows a very reliable and simple mechanism of detecting an earth fault in the brake circuit as well as to provide the necessary measures to take the elevator smoothly out of service, preferably after having driven the elevator car to a nearby door zone.

[0038] In a preferred embodiment, the safety device could indicate to the control device 40 of the elevator to drive the elevator car to the next landing in travelling direction so as to reduce the length of the elevator travel after having detected the earth fault in the brake circuit.

[0039] The invention is not restricted to the disclosed embodiment but may be varied within the scope of the attached patent claims.

LIST OF REFERENCE NUMBERS

[0040] 10 galvanically separating link componentDC/DC converter

[0041] 11 brake drive

[0042] 12 brake coil

[0043] 14 rectifying diode

[0044] 16 smoothing capacitor

[0045] 18 varistor

[0046] 19 second diode

[0047] 20 brake circuit

[0048] 21 third diode in the earth fault indicator circuit

[0049] 22 earth fault indicator circuit

[0050] 23 resistor of the earth fault indication circuit, preferably with a resistance in the k area

[0051] 24 LEDtransmitting part of opto-coupler

[0052] 26 galvanically isolating transmission elementopto-coupler

[0053] 27 earth fault transmission circuit

[0054] 28 receiving part of opto-coupler

[0055] 30 safety device

[0056] 32 location sensor

[0057] 34a,b earth fault connections

[0058] 36 delay circuit

[0059] 38 succession circuit

[0060] 40 control device

[0061] Q1 first semiconductor switchfirst transistor, particularly PWM modulated

[0062] Q2 second semiconductor switchsecond transistor