DRIVE OF AN ELEVATOR SYSTEM

Abstract

An elevator system drive includes: an electric machine: a first converter electrically connected to an alternating current source and the electric machine: a drive controller controlling the drive: a drive safety circuit unit electrically connected to a safety circuit of the elevator system, to a controller of the elevator system, and to the drive controller; and at least one mechanical brake that is closed by a brake closing command from the elevator system controller. The drive safety circuit unit operates in a first operating state wherein it transmits an emergency stop command coming from the elevator system safety circuit directly and without delay to the first converter, and operates in a second operating state wherein it relays a modified emergency stop command coming from the elevator system safety circuit, with a delay, to the first converter to ensure safe braking of the elevator system even if the mechanical brakes fail.

Claims

1-15. (canceled)

16. A drive for an elevator system, the drive comprising: an electric machine adapted to rotate for moving an elevator car of the elevator system; a converter electrically connected to the electric machine to provide energy from an alternating current source to rotate the electric machine; a drive controller controlling the converter; a drive safety circuit unit electrically connected to a safety circuit of the elevator system, to a controller of the elevator system, and to the drive controller; a mechanical brake that is closed by a brake closing command of the controller of the elevator system to stop the rotation of the electric machine; wherein the drive safety circuit unit is adapted to operate in a first operating state and in a second operating state; and wherein the drive safety circuit unit operates in the first operating state to transmit an emergency stop command generated by the safety circuit of the elevator system directly and without delay to the converter to close the mechanical brake, and operates in the second operating state to transmit the emergency stop command from the safety circuit of the elevator system to the converter with a delay.

17. The drive according to claim 16 wherein the drive safety circuit unit operates in the first operating state when the mechanical brake is open and at least temporarily changes to the second operating state in response to the brake closing command.

18. The drive according to claim 17 wherein the drive safety circuit unit remains in the second operating state, or changes to the first operating state, after changing to the second operating state, depending on a functionality of the mechanical brake, wherein the drive safety circuit unit remains in the second operating state when the mechanical brake is defective, and the drive safety circuit unit changes to the first operating state when the mechanical brake is functioning.

19. The drive according to claim 16 wherein during the second operating state of the drive safety circuit unit, the emergency stop command, that in the first operating state of the drive safety circuit unit immediately deactivates the drive controller and causes an immediate demagnetization of the electric machine, is delayed to prevent the immediate deactivation of the drive controller and to maintain a magnetization of the electric machine despite the emergency stop command.

20. The drive according to claim 16 wherein the mechanical brake includes a brake contact monitoring an operating state of the mechanical brake and generating a signal indicating whether the operating state is in an open brake operating state or a closed brake operating state, and wherein the drive safety circuit unit is connected to the brake sensor contact and responds to the signal to determine the operating state of the mechanical brake.

21. The drive according to claim 16 wherein the electric machine includes a rotation sensor measuring a rotation of the electric machine and generating a signal indicating whether the electric machine is rotating, and wherein the drive safety circuit unit is connected to the rotation sensor and responds to the signal to determine whether the electric machine is rotating or stationary.

22. The drive according to claim 16 wherein the converter is a bidirectional converter and the drive safety circuit unit when in the second operating state controls the bidirectional converter to operate the electric machine in a generator mode.

23. The drive according to claim 16 wherein the converter is a first converter, wherein a second converter is connected to the electric machine at a machine alternating current output of the second converter connected electrically parallel to a machine alternating current output of the first converter, wherein the electric machine is an induction machine, and wherein the drive safety circuit unit includes a converter controller controlling the second converter.

24. The drive according to claim 16 wherein the mechanical brake includes a first mechanical brake and a second mechanical brake each closed in response to the brake closing command.

25. An elevator system comprising: a drive according to claim 16; a controller of the elevator system connected to the drive; and a safety circuit of the controller generating a safety circuit signal to the drive for triggering an emergency stop of the elevator system.

26. A method for operating a drive according to claim 16 to brake an elevator system, the method comprising the steps of: transmitting a closing command to a mechanical brake for braking an elevator car of the elevator system; verifying a braking effect of the mechanical brake after the closing command has been transmitted to the mechanical brake by comparing an actual braking effect of the mechanical brake with a target braking effect; and using the electric machine of the drive to brake the elevator car when a deviation of the actual braking effect from the target braking effect is determined by the comparing and the braking effect has been verified.

27. The method according to claim 26 wherein the comparing of the actual braking effect with the target braking effect includes the steps of: verifying whether a brake contact of the mechanical brake is signaling a closed state of the mechanical brake; reducing a holding torque exerted by the electric machine when the closed state is verified; and verifying whether a rotation sensor is signaling a rotation of the electric machine or a position sensor is signaling a movement of the elevator car.

28. The method according to claim 27 the step of using the electric machine to brake including building up a torque produced by the electric machine to the holding torque.

29. The method according to claim 27 wherein the electric machine is an induction machine, wherein at least one of a current and a voltage of the electric machine and a phase position of the at least one of the current and the voltage are measured before the holding torque is reduced, and wherein when the torque is built up, at least one of a voltage and a current is generated that corresponds to the measured at least one of the voltage and the current in the measured phase position.

30. A method of operating a drive of an elevator system, the elevator system having a mechanical first brake and a mechanical second brake for braking an elevator car of the elevator system in a normal operation, the method comprising the step of using the drive as a third brake for braking the elevator car when the first brake and the second brake in a closed state cannot hold the elevator car.

31. The method according to claim 30 including ensuring that the drive is not demagnetized when changing from the normal operation, wherein the drive functions as a drive of the elevator system, to an operation in which the drive is used as the third brake by not switching off the drive.

Description

DESCRIPTION OF THE DRAWINGS

[0039] In the following, the invention is further explained in drawings with reference to embodiments, in which:

[0040] FIG. 1 is a schematic representation of an elevator system.

[0041] FIG. 2 is a first embodiment of a drive according to the invention.

[0042] FIG. 3 is a second embodiment of a drive according to the invention.

[0043] FIG. 4 is a schematic representation of a method according to the invention for operating a drive for an elevator system.

DETAILED DESCRIPTION

[0044] FIG. 1 shows an elevator system 3, the elevator system having a drive 1. In this embodiment, the drive 1 consists of an electric machine 5, which in this case is designed as an induction machine. The drive 1 is used in the elevator system 3 to move an elevator car 4. The movement of the elevator car 4 in the shaft of the elevator system is monitored by a position sensor 29.

[0045] FIG. 2 shows a drive 1 of the elevator system 3 according to the invention in a first embodiment. The drive comprises an electric machine 5, which in this exemplary embodiment is designed as an induction machine. The drive further comprises a first converter 7, which in this exemplary embodiment is designed as a bidirectional converter. The converter 7 converts electrical energy which comes from the alternating current source 9 into a form of energy suitable for driving the electric machine 5. The converter 7 has current sensors “I” on the AC current source 9 side, with one current sensor per phase. The converter 7 also has one current sensor per phase on the side of the electric machine 5. The measured values of these current sensors are used in the drive controller 11 in order to control the switching elements of the converter 7, which in this embodiment are designed as IGBTs. The converter 7 thus enables the generation of a voltage with a variable amplitude and a variable frequency. The electric machine 5 can thus be operated at different operating points. The electric machine 5 is equipped with a first mechanical brake 19. This first mechanical brake 19 makes it possible to bring the electric machine 5 to a standstill. In this exemplary embodiment, the electric machine 5 comprises a second mechanical brake 20. The second mechanical brake 20 is a brake that is redundant to the first mechanical brake. The first mechanical brake 19 and the second mechanical brake 20 each include a brake contact 21. In this embodiment, the brake contact 21 is designed as a switch which is actuated when the first or the second mechanical brake is closed. The electric machine comprises a rotation sensor 23. A brake signal 22 is routed from the brake contact 21 to the drive safety circuit unit 13. A signal line with the signal 24 from the rotation sensor also leads from the rotation sensor 23 to the drive safety circuit unit 13. The drive safety circuit unit 13 has an input for the signal 28 of the position sensor 29 (see FIG. 1). The drive safety circuit unit 13 also has an input via which the safety circuit signal 15 of the controller of the elevator system 17 is routed to the drive safety circuit unit 13. It also has an output for the signal 24 from the rotation sensor 23 which is routed via this output, and a line from the drive safety circuit unit 13 routed to the drive controller 11. There is also a connection which carries the signal 30 of the elevator controller from the elevator controller 17 to the drive controller 11. The connection between the safety circuit of the elevator controller 17 and the drive safety circuit unit 13 enables the safety circuit signal 15 of the controller of the elevator system 17 to be routed via the drive safety circuit unit 13, from where it continues on to the drive controller 11. This enables the drive safety circuit unit 13 to relay the signal of the safety circuit to the elevator controller 17 with a delay. The drive safety circuit unit 13 decides on the delay of the safety circuit signal based on the signal from the position sensor 29 and/or the rotation sensor 23, and based on the signal from the brake contact 21. The drive safety circuit unit 13 verifies the braking effect of the first mechanical brake 19 and the second mechanical brake 20 as soon as a corresponding signal from the brake contact 21 and the other brake contact (second mechanical brake) arrives. The verification of the braking effect of the first mechanical brake 19 and the second mechanical brake 20 takes place via the signal 28 from the position sensor 29 and the signal 24 from the rotation sensor 23. If, after the brake contact of the first mechanical brake 19 and the second mechanical brake 20 is closed, a rotation is detected by the rotation sensor 23 or a movement is detected by the position sensor 29, it can be concluded that the braking effect of the first mechanical brake 19 and the second mechanical brake 20 is insufficient. In this case, the safety circuit signal 15 which comes from the elevator controller 17 is delayed, such that the drive controller 11 continues to function—that is to say, it operates the converter 7 in such a way that the electric machine 5 remains magnetized. This enables the use of the electric machine 5 as an additional braking element. This would not be possible if the safety circuit were to put the converter 7, in particular the drive controller 11, directly out of operation. In this case, the converter 7 and the electric machine 5 would have to be restarted and/or re-magnetized. This would lead to a loss of valuable time, such that the braking effect of the drive, that is to say of the electric machine 5, would only start after a great delay. The drive safety circuit unit 13 thus enables the drive 1 to be used directly as an additional braking element in the event that the first mechanical brake 19 and the second mechanical brake 20 do not produce the desired braking power. The signal 24 from the rotation sensor 23 is required by the drive safety circuit unit 13, and is then passed on to the drive controller 11, where it is also used to control the electric machine.

[0046] FIG. 3 shows a second embodiment of a drive 1 according to the invention. The identical elements already described above are not described again here. Reference is made to the preceding description. In this second exemplary embodiment, the drive 1 comprises a second converter 25 in addition to the first converter 7. The second converter 25 is electrically connected to the electric machine 5 in parallel with the first converter 7. This enables the second converter 25 to take over the function of the first converter 7. For this purpose, the drive 1 includes a further converter controller 27, which is formed in the drive safety circuit unit 13. This converter controller 27 controls the second converter 25. This makes it possible for the second converter 25 and the corresponding converter controller 27 to take on the task of braking the electric machine 5 if the alternating current source 9 fails. The braking described in the foregoing and in the following can thus also be exercised by the electric machine when the electrical grid, that is to say the alternating current source 9, has failed. For this purpose, the second converter 25 has a brake resistor and an electrical switch (not shown) with which the brake resistor can be optionally connected to the intermediate circuit of the converter. This makes it possible to degrade the energy that flows from the electric machine 5 into the converter 25 when the electric machine 5 is braked. A system that is independent of the alternating current source 9 is thereby achieved.

[0047] FIG. 4 shows a schematic representation of a method for operating a drive 1 according to the invention. The method comprises the following steps:

[0048] The elevator car moves to an appropriate floor in step 31, the converter holds the car at this floor in step 33, the brake closes in step 35, the brake contact reports that the brake is closed in step 37, and the converter reduces the torque in step 39. In step 41, a decision is made as to whether the braking effect of the first mechanical brake and optionally the second mechanical brake is sufficient. If it is determined by the rotation sensor 23 that the elevator car 4 is not moving, then the converter reports in step 43 that everything is okay. In step 45 the converter is switched off. The elevator controller opens the safety circuit 15 in step 47. If, however, it is determined that the elevator car 4 is moving, that is to say that the rotation sensor 23 and/or the position sensor 29 is detecting a movement, then in step 49 a movement is detected. The converter then builds up a torque again, or increases the torque, in step 51. As such, in step 53, the car is held by the converter, or is optionally held/braked by the converter and the mechanical brake. The converter then demands safe halting of the elevator car 4 in step 53. In step 55, the drive controller 11 accordingly initiates the method for safely halting the elevator car 4. In step 57, the elevator car is placed on the buffer where it is safely halted. In step 59, it is then reported that the elevator car is safely placed. In step 61, the safety circuit is fully opened.

[0049] In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.