Motor drive apparatus configured to determine cause of DC link voltage fluctuation

Patent metadata

Field	Value
Publication number	US-11211892-B2
Application number	US-202016951008-A
Country	US
Kind code	B2
Filing date	Nov 18, 2020
Priority date	Dec 3, 2019
Publication date	Dec 28, 2021
Grant date	Dec 28, 2021

Abstract

A motor drive apparatus includes: a rectifier; an inverter; a DC link voltage detection unit; an input current detection unit configured to detect input current inputted to the rectifier; a DC link voltage comparison unit configured to compare a DC link voltage with a first voltage threshold value and with a second voltage threshold value; a current comparison unit configured to compare the input current with a current threshold value; and an abnormality detection unit configured, in a case that the DC link voltage is smaller than the first voltage threshold value or that the DC link voltage is greater than the second voltage threshold value, to determine that a first abnormality has occurred when the input current is smaller than the current threshold value and to determine that a second abnormality has occurred when the input current is equal to or greater than the current threshold value.

First claim

The invention claimed is:

1. A motor drive apparatus comprising:
a rectifier configured to convert AC power inputted from an AC input side to DC power and to output the DC power to a DC link which is on a DC output side;
an inverter configured to convert DC power in the DC link to AC power for driving a motor and to output the AC power;
a DC link voltage detection unit configured to detect DC link voltage, which is voltage between terminals of the DC link;
an input current detection unit configured to detect input current inputted to the rectifier from the AC input side;
a DC link voltage comparison unit configured to compare the DC link voltage with a first voltage threshold value and with a second voltage threshold value, which is set at a greater value than the first voltage threshold value;
a current comparison unit configured to compare the input current with a current threshold value; and
an abnormality detection unit configured, in a case in which the DC link voltage comparison unit has determined that the DC link voltage is smaller than the first voltage threshold value or that the DC link voltage is greater than the second voltage threshold value, to determine that a first abnormality has occurred when the current comparison unit has determined that the input current is smaller than the current threshold value and to determine that a second abnormality has occurred when the current comparison unit has determined that the input current is equal to or greater than the current threshold value.

2. The motor drive apparatus according to claim 1 , further comprising:
a first switching unit provided on the AC input side of the rectifier and configured to open and close a current path of the input current from the AC input side to the rectifier; and
a second switching unit provided between an AC power supply, which is a supply source of AC power inputted to the rectifier, and the first switching unit and configured to open and close a current path from the AC power supply to the first switching unit.

3. The motor drive apparatus according to claim 2 ,
wherein the first abnormality includes at least one of a prolonged power failure of the AC power supply, a momentary power failure of the AC power supply, a state of the current path being open caused by the first switching unit, and a state of the current path being open caused by the second switching unit, and
wherein the second abnormality includes at least one of a failure in the motor drive apparatus, an overload on the motor drive apparatus, and a capacity shortage of the AC power supply.

4. The motor drive apparatus according to claim 3 , further comprising:
an input voltage detection unit configured to detect input voltage, which is phase voltage between the first switching unit and the second switching unit; and
an input voltage comparison unit configured to compare the input voltage with a power failure threshold value when the DC link voltage comparison unit has determined that the DC link voltage is smaller than the first voltage threshold value or that the DC link voltage is greater than the second voltage threshold value,
wherein the abnormality detection unit
determines that a momentary power failure of the AC power supply has occurred when the input voltage comparison unit has determined that a state in which the input voltage is equal to or smaller than the power failure threshold value continued for less than a predefined time period, and
determines that either a state of the current path being open caused by the second switching unit or a prolonged power failure of the AC power supply has occurred when the input voltage comparison unit has determined that a state in which the input voltage is equal to or smaller than the power failure threshold value continued for the predefined time period or more.

5. The motor drive apparatus according to claim 4 , wherein the abnormality detection unit determines that a state of the current path being open caused by the first switching unit has occurred when the input voltage comparison unit has determined that the input voltage is greater than the power failure threshold value.

6. The motor drive apparatus according to claim 2 , wherein the first switching unit is an electromagnetic contactor.

7. The motor drive apparatus according to claim 2 , wherein the second switching unit is a breaker.

Assignees

• Fanuc Corp

Inventors

• Tagawa Takaaki

Classifications

• H02P27/08

  with pulse width modulation · CPC title

• H02P2201/03

  AC-DC converter stage controlled to provide a defined DC link voltage · CPC title

• G01R31/42

  AC power supplies · CPC title

• H02P29/026 Primary

  the fault being a power fluctuation · CPC title

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title