Motor control device and air-conditioning device

Patent metadata

Field	Value
Publication number	US-11424698-B2
Application number	US-201917294466-A
Country	US
Kind code	B2
Filing date	Jan 16, 2019
Priority date	Jan 16, 2019
Publication date	Aug 23, 2022
Grant date	Aug 23, 2022

Abstract

A motor control device includes: an inverter circuit configured to convert a direct-current voltage into an alternating-current voltage, and to supply the alternating-current voltage to a plurality of motors connected in parallel; current detectors configured to detect motor currents flowing through the respective motors; a relay provided between at least one of the plurality of motors and the inverter circuit; and a controller configured to change the number of motors to be driven. When one of two or more motors under driving is stopped, the controller lowers a current instruction value to the two or more motors under driving. When a monitor current that is the motor current detected by the current detector of the motor connected to the relay is decreased, the controller switches the relay from an on state to an off state.

First claim

The invention claimed is:

1. A motor control device, comprising:
an inverter circuit configured to convert a direct-current voltage into an alternating-current voltage, and to supply the alternating-current voltage to a plurality of motors connected in parallel;
current detectors configured to detect motor currents flowing through the respective motors;
a relay provided between at least one of the plurality of motors and the inverter circuit and configured to switch an on state and an off state of connection between the one motor and the inverter circuit; and
a controller configured to change number of motors to be driven out of the plurality of motors, wherein
the controller lowers, when one of two or more motors under driving is stopped, a current instruction value to the two or more motors under driving, and switches, when a monitor current that is the motor current detected by the current detector of the motor connected to the relay is decreased, the relay connected to a motor to be stopped, from the on state to the off state.

2. The motor control device of claim 1 , wherein the controller compares the monitor current with a determined first threshold, and in a case where the monitor current is less than the first threshold, the number-of-motors change unit switches the relay from the on state to the off state.

3. The motor control device of claim 2 , wherein
the controller calculates an exciting current instruction value to stabilize rotation of the motor to be stopped, based on a phase difference between a phase estimated from the motor current of the motor under driving and a phase estimated from the monitor current, calculates a torque current instruction value based on a rotation speed difference between a rotation speed instruction value and a rotation speed estimated from a parameter value including the motor current of the motor under driving, calculates a first control amount from a current difference between the torque current instruction value and a torque current corresponding to the motor current of the motor under driving, and calculates a second control amount from a current difference between the exciting current instruction value and an exciting current corresponding to the motor current of the motor under driving, the coordinate conversion unit generating a voltage instruction value to be output to the inverter circuit, based on the first control amount and the second control amount,
when the one motor is stopped, the controller stops the calculation of the exciting current instruction value and the calculation of the torque current instruction value, and
when the monitor current is reduced to the first threshold, the controller switches the relay from the on state to the off state.

4. The motor control device of claim 2 , wherein
the controller estimates a rotation speed of the motor connected to the relay, based on the monitor current,
in a case where the monitor current is larger than or equal to the first threshold, the controller compares the monitor current with a second threshold greater than the first threshold and compares the rotation speed estimated with a determined rotation speed threshold, and
in a case where both of a first condition that the monitor current is less than the second threshold and a second condition that the estimated rotation speed is less than the rotation speed threshold are satisfied, the number-of-motors change unit switches the relay from the on state to the off state.

5. The motor control device of claim 4 , wherein
the controller includes a timer measuring an elapsed time after reduction of the motor currents flowing through the two or more motors under driving,
in a case where at least one of the first condition and the second condition is not satisfied, the controller compares the elapsed time with a determined threshold time,
in a case where both of the first condition and a third condition that the elapsed time is longer than the threshold time are satisfied, the controller switches the relay from the on state to the off state, and
in a case where at least one of the first condition and the third condition is not satisfied, the controller determines that a device including the motor connected to the relay has abnormality.

6. An air-conditioning device, comprising:
a refrigerant circuit through which refrigerant circulates, the refrigerant circuit including a compressor, a condenser, an expansion device, and an evaporator that are connected to one another;
a fan configured to supply air to at least one of the condenser and the evaporator;
the plurality of motors connected to one or both of the compressor and the fan; and
the motor control device of claim 1 .

7. A motor control device, comprising:
an inverter circuit configured to convert a direct-current voltage into an alternating-current voltage, and to supply the alternating-current voltage to a plurality of motors connected in parallel;
current detectors configured to detect motor currents flowing through the respective motors;
a relay provided between at least one of the plurality of motors and the inverter circuit and configured to switch an on state and an off state of connection between the one motor and the inverter circuit; and
a controller configured to change number of motors to be driven from the plurality of motors, wherein
the controller makes a rotation speed of a motor under driving smaller than a rotation speed instruction value when the number of motors to be driven is increased by one, and switches when a monitor rotation speed that is a rotation speed estimated from the motor current detected by the current detector of the motor under driving is less than the rotation speed instruction value, the relay connected to a motor to be activated, from the off state to the on state.

8. The motor control device of claim 7 , wherein
the controller compares the monitor rotation speed with a determined first threshold, and
in a case where the monitor rotation speed is less than the first threshold, the number-of-motors change unit switches the relay from the off state to the on state.

9. The motor control device of claim 8 , wherein
the controller calculates a torque current instruction value based on a rotation speed difference between the rotation speed instruction value and a rotation speed estimated from a parameter value including the motor current of the motor under driving, calculates a first control amount from a current difference between the torque current instruction value and a torque current corresponding to the motor current of the motor under driving, and calculates a second control amount from a current difference between a value corresponding to a type of the plurality of motors and an exciting current corresponding to the motor current of the motor under driving, generates a voltage instruction value to be output to the inverter circuit, based on the first control amount and the second control amount,
when the number of motors to be driven is increased by one, the controller sets the rotation speed instruction value to zero, and
when the monitor rotation speed is reduced to the first threshold, the controller switches the relay from the off state to the on state.

10. The motor control device of claim 8 , wherein
the controller estimates a regenerative voltage based on the motor current detected by the current detector of a motor under driving,
in a case where the monitor rotation speed is greater than or equal to the first threshold, the controller compares the monitor rotation speed with a second threshold greater than the first threshold, and compares the regenerative voltage estimated by the inverter control unit with a determined voltage th

Assignees

• Mitsubishi Electric Corp

Inventors

• Tsumura Akihiro
• Shimizu Yuichi
• Wada Yasuhiko
• Morimoto Junji

Classifications

• H02P5/46

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

• H02P21/00

  Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation · CPC title

• H02P5/74 Primary

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

• H02P29/028 Primary

  the motor continuing operation despite the fault condition, e.g. eliminating, compensating for or remedying the fault · CPC title

• H02P27/06

  using DC to AC converters or inverters (H02P27/05 takes precedence) · CPC title