System and method for starting high inertia machines

Abstract

A drive system for a working machine with a working device which can be unloaded for starting, wherein the drive system comprises at least one main motor, which is designed as an electric machine, in particular as an asynchronous motor, and a motor shaft; an auxiliary motor, which is designed as an electric machine, in particular as an asynchronous motor; and a starting device for starting the auxiliary motor. The auxiliary motor is configured to start and/or accelerate the working machine, in particular up to a synchronous speed of the main motor.

Claims

1-15. (canceled)

16. A drive system for a working machine with a working device that can be unloaded for starting the machine, the drive system comprising: at least one main motor designed as an electric machine, and including a motor shaft; an auxiliary motor designed as an electric machine; and a starting device for starting the auxiliary motor; wherein the auxiliary motor is configured to at least one of start or accelerate the working machine.

17. The drive system of claim 16, wherein at least one of: at least one of the at least one main motor or the at least one auxiliary motor is configured as an asynchronous motor; or the auxiliary motor is configured to at least one of start or accelerate the working machine up to a synchronous speed of the main motor.

18. The drive system of claim 16, wherein at least one of: the auxiliary motor has at least 1/10 of the power of the main motor; or the auxiliary motor has at most of the power of the main motor.

19. The drive system of claim 16, wherein the main motor is one of a squirrel-cage rotor, an asynchronous motor, a doubly-fed asynchronous motor, an externally excited synchronous motor, or a permanent-magnet excited synchronous motor.

20. The drive system of claim 16, wherein: the motor shaft has a first end and an oppositely disposed second end; the first end of the motor shaft configured to provide power output; and the auxiliary motor is arranged at the second end of the motor shaft, parallel to the main motor, or between the main motor and a subsequent transmission.

21. The drive system of claim 16, wherein the auxiliary motor is configured for use in a maintenance operation of the working machine.

22. The drive system of claim 16, further comprising: a switchable clutch or an overrunning clutch operatively connecting the auxiliary motor to the main motor.

23. The drive system of claim 16, wherein: the starting device is configured as a star-delta circuit; and the auxiliary motor is started with the star-delta circuit by reducing a starting current of the drive system.

24. The drive system of claim 16, wherein: the auxiliary motor, in cooperation with the starting device, is configured to adjust a rotational speed in such a way that when the main motor is switched on, a valid synchronous rotational speed is present for a mains frequency measured in a supply network that provides power to the drive system.

25. The drive system of claim 24, wherein the starting device is designed as a frequency converter.

26. The drive system of claim 16, wherein the main motor comprises at least two independent winding systems, each of which can be connected independently to a power supply system.

27. The drive system of claim 16, wherein: the at least one main motor is one of: exactly one main motor, at least two main motors, or no more than 10 main motors; and each main motor is connected independently to a power supply system.

28. A working machine, comprising: a drive system according to claim 16; and a working device; wherein the working machine is adapted to unload the at least one working device.

29. The working machine of claim 28, wherein the working machine is configured as a vertical roller mill.

30. A method for operating a working machine, the working machine including at least one working device and a drive system comprising at least one main motor designed as an electric machine and having a motor shaft, an auxiliary motor designed as an electric machine, and a starting device for starting the auxiliary motor, wherein the auxiliary motor is configured to at least one of start or accelerate the working machine, the method comprising: unloading the at least one working device of the working machine; starting the drive system with the starter-actuated auxiliary motor; and switching on the main motor at synchronous speed of a supply network.

31. The method of claim 30, wherein the working machine is a vertical roller mill.

32. The method of claim 30, further comprising: measuring a mains frequency; and adjusting the speed of the working machine with the auxiliary motor so that the currently valid synchronous speed is present when the main motor is switched on.

33. The method of claim 32, wherein the speed is adjusted dynamically.

34. The method of claim 30, further comprising one of: switching the auxiliary motor to an overload operation in a time period with a duration of less than 2 seconds while the main motor is operated at a setpoint speed; switching the auxiliary motor to an operation without load takeover in a time period with a duration of less than 2 seconds while the main motor is operated at a setpoint speed; or at least one of starting or operating the auxiliary motor in parallel with the main motor.

35. The method of claim 34, wherein the at least one of starting or operating the auxiliary motor is based on a determined load of the main motor.

36. The method of claim 30, further comprising: continuing to operate the auxiliary motor with the main motor during operation of the main motor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the principles of the invention.

[0052] FIG. 1 schematically illustrates a drive system according to one embodiment of the present invention;

[0053] FIG. 2 illustrates a method according to one embodiment of the present invention; and

[0054] FIG. 3 schematically depicts a drive system according to one embodiment of the present invention.

DETAILED DESCRIPTION

[0055] FIG. 1 schematically shows a drive system 1 as described in embodiments herein. The drive system 1 comprises a main motor 2 which can be or is switched via a medium voltage circuit breaker 5. Further shown is an auxiliary motor 3 disposed on a second end of the shaft of the main motor 1. The auxiliary motor 3 shown is controlled or operated by a frequency converter 4 in a variable speed manner. The first end of the shaft is coupled here to a gearbox 6 of a mill, or is operatively connected to it.

[0056] FIG. 2 schematically shows a procedure with the steps S10 to S50. In a step S10, a mains frequency can be measured, preferably optionally (shown by the dashed line). According to the measured mains frequency, in a further, in particular optional step S20 (also represented by dashing), a (set) speed can be adjusted, preferably dynamically, in such a way that when the main motor S50 is switched on, the currently valid synchronous speed is (at least essentially) present. In a further step S30, the at least one working device of the working machine, preferably all working devices of the working machine, is unloaded. In a step S40, after unloading the working device of the working machine, preferably all working devices, the drive system, preferably the auxiliary motor, is started by means of the starting device 4. The main motor is switched on in a step S50 when at least substantially a synchronous speed is reached.

[0057] FIG. 3 schematically shows a drive system 1 as described in embodiments herein. The drive system 1 has several, here preferably two, main motors 2, which can preferably be switched via a medium-voltage circuit breaker 5. Furthermore, an auxiliary motor 3 is shown in each case, which is arranged at a second end of the shaft of the main motor 1. In dashed lines, an auxiliary motor is shown in each case in an alternative arrangement at the first shaft end of the shaft of the main motors 1. The auxiliary motors 3 shown are controlled or operated with variable speed by a starting device 4. The first shaft end of the main motors 2 is in each case schematically coupled to a gear unit 6 of a mill, or operatively connected thereto, for example via a summation gear unit (not shown).

[0058] Although exemplary embodiments have been explained in the preceding description, it should be noted that a variety of variations are possible. Furthermore, it should be noted that the exemplary embodiments are merely examples that are not intended to limit the scope of protection, applications or construction in any way. Rather, the foregoing description provides the skilled person with a guide for implementing at least one exemplary embodiment, wherein various modifications, particularly with respect to the function and arrangement of the described components, may be made without departing from the scope of protection as it results from the claims and from these equivalent feature combinations.

[0059] While the present invention has been illustrated by a description of various embodiments, and while these embodiments have been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such de-tail. The various features shown and described herein may be used alone or in any combination. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method, and illustrative example shown and described. Accordingly, departures may be made from such details without departing from the spirit and scope of the general inventive concept.

LIST OF REFERENCE SIGNS

[0060] 1 Drive system [0061] 2 Main engine [0062] 3 Auxiliary motor [0063] 4 Starting device [0064] 5 Medium voltage circuit breaker [0065] 6 Gearbox [0066] S10 Measuring a mains frequency [0067] S20 Adjusting the speed [0068] S30 Lifting the roller(s) [0069] S40 Starting the drive system/auxiliary motor [0070] S50 Switching on the main motor.