Electric motor control device

Patent metadata

Field	Value
Publication number	US-11196361-B2
Application number	US-201716635299-A
Country	US
Kind code	B2
Filing date	Oct 3, 2017
Priority date	Oct 3, 2017
Publication date	Dec 7, 2021
Grant date	Dec 7, 2021

Abstract

An electric motor control device controls driving of electric motors connected in parallel with each other and includes a power converter converting power from a power supply, and supply the converted power to each of the electric motors, a switching device to be turned on to electrically connect the power converter and at least one of the electric motors and to be turned off to electrically disconnect the power converter and the at least one of the electric motors, a current detection unit detecting a current that flows in the electric motors, and a controller controlling the power converter on the basis of operation of the switching device, rotation frequency command values from an external device, and a value of the current detected by the current detection unit. The controller turns the switching device from off to on so that start timing of control is different for each electric motor.

First claim

The invention claimed is:

1. An electric motor control device that controls driving of a plurality of electric motors connected in parallel with each other, the electric motor control device comprising:
a power converter configured to convert power from a power supply, and supply the converted power to each of the plurality of electric motors;
a switching device configured to be turned on to electrically connect the power converter and at least one of the plurality of electric motors and configured to be turned off to electrically disconnect the power converter and the at least one of the plurality of electric motors;
a current detection unit configured to detect a current that flows in the plurality of electric motors; and
a controller configured to control the power converter on a basis of operation of the switching device, rotation frequency command values from an external device, and a value of the current detected by the current detection unit,
the controller being configured to perform control for turning the switching device from off to on in such a manner that start timing of control for decelerating the at least one of the plurality of electric motors is different from start timing of control for decelerating remaining at least one of the plurality of electric motors.

2. The electric motor control device of claim 1 , wherein
the controller is configured to perform a process of deriving a rotation frequency estimation value of the remaining at least one of the plurality of electric motors on a basis of a phase and amplitude of an induced voltage in the remaining at least one of the plurality of electric motors obtained from the value of the current detected by the current detection unit, and,
when the controller determines that set time corresponding to the rotation frequency estimation value elapses after start of control for decelerating the remaining at least one of the plurality of electric motors at first, the controller is configured to turn the switching device from off to on.

3. The electric motor control device of claim 2 , wherein, after the controller determines set time elapses, the controller is configured to cause a DC voltage from the power converter to be applied to the remaining at least one of the plurality of electric motors for preset time, and turn the switching device from off to on.

4. The electric motor control device of claim 1 , wherein the controller is configured to turn the switching device from off to on when the controller determines that the value of the current detected by the current detection unit is not more than a set current after start of control for decelerating the remaining at least one of the plurality of electric motors at first.

5. The electric motor control device of claim 1 , wherein
the power converter has a pair of switching elements that are an upper switching element and a lower switching element provided to each phase of the plurality of electric motors, and
the controller is configured to turn on the upper switching elements of all phases that the power converter has or the lower switching elements of the all phases, and decelerate at least one of the plurality of electric motors.

6. The electric motor control device of claim 5 , wherein, when the controller decelerates at least one of the plurality of electric motors, the controller is configured to output, to the power converter, a pulsatile signal for repeating on and off of the upper switching elements of the all phases or the lower switching elements of the all phases, and then output, to the power converter, a signal for keeping the upper switching elements or the lower switching elements turned on.

7. The electric motor control device of claim 5 , wherein the pair of switching elements are each an element having a wide bandgap semiconductor.

8. The electric motor control device of claim 7 , wherein the wide bandgap semiconductor is made from silicon carbide-based material, gallium nitride-based material, or diamond.

9. The electric motor control device of claim 1 , wherein the controller is configured to stop operation of the power converter on a basis of the current detected by the current detection unit when the switching device is turned on.

Assignees

• Mitsubishi Electric Corp

Inventors

• Wada Yasuhiko
• Tsumura Akihiro

Classifications

• H02P3/025

  holding the rotor in a fixed position after deceleration · CPC title

• H02P5/74 Primary

  controlling two or more AC dynamo-electric motors (H02P5/46, H02P5/60 take precedence) · CPC title

• H02P29/02

  Providing protection against overload without automatic interruption of supply (protection against faults of stepper motors H02P8/36) · CPC title

• H02P6/04

  Arrangements for controlling or regulating the speed or torque of more than one motor (H02P6/10 takes precedence) · CPC title

• H02P5/46

  for speed regulation of two or more dynamo-electric motors in relation to one another · CPC title