MOTOR CONTROL DEVICE INCLUDING ELECTRIC STORAGE DEVICE AND RESISTANCE DISCHARGE DEVICE

• US 20140210389A1
• Filed: 01/28/2014
• Published: 07/31/2014
• Est. Priority Date: 01/29/2013
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: Niwa, Masakazu, Yamamoto, Kenta
• Granted Patent: US 9,118,270 B2
• Time in Patent Office: Days
• US Class Current: 318/400.3
• CPC Class Codes: H02P 2201/03 AC-DC converter stage controlled to provide a defined DC link voltage general aspects of plural converters in cascade H02M
• CPC Class Codes: H02P 3/12 by short-circuit or resistive braking
• CPC Class Codes: H02P 3/14 by regenerative braking
• CPC Class Codes: H02P 3/22 by short-circuit or resistive braking
• CPC Class Codes: H02P 5/74 controlling two or more ac dynamo-electric motors H02P5/46, H02P5/60 take precedence

Abstract

A motor control device includes a rectifier, an inverter connected to the rectifier via the DC link, a power failure detecting unit detecting power failure, a voltage detecting unit detecting a DC voltage at the DC link, an electric storage unit storing DC power, a charging unit that can make charging by boosting to a voltage higher than the DC voltage, a discharging unit discharging DC power, a resistance discharge device that performs resistance discharging of DC power at the DC link when the DC voltage after power failure is equal to or higher than a predetermined start level and that does not perform resistance discharging when the DC voltage is equal to or lower than a predetermined stop level, and a discharging operation determining unit operating the discharging unit when the DC voltage at the DC link after power failure is equal to or lower than a predetermined threshold.

Claims

1. A motor control device comprising:

a rectifier that rectifies AC power supplied from an AC side to output DC power;

an inverter that is connected to a DC link at a DC side of the rectifier, and performs interconversion of electric power between DC power at the DC link and drive power for a motor or regenerative electric power, which are AC power;

a power failure detecting unit that detects power failure at the AC side of the rectifier;

a voltage detecting unit that detects a DC voltage value at the DC link;

an electric storage device that is connected to the DC link, and stores DC power;

a charging unit that has a boosting function of charging the electric storage device at a voltage higher than a DC voltage at the DC link;

a discharging unit that makes short-circuiting between the electric storage device and the DC link to discharge DC power stored in the electric storage device to the DC link;

a resistance discharge device that is connected to the DC link wherein after the power failure detecting unit detects power failure, the resistance discharge device starts resistance discharging operation of consuming DC power of the DC link by resistance discharging when a DC voltage value detected by the voltage detecting unit is equal to or higher than a resistance discharging start level, and the resistance discharge device stops the resistance discharging operation when the DC voltage value detected by the voltage detecting unit is equal to or lower than a resistance discharging stop level lower than the resistance discharging start level; and

a discharging operation determining unit that does not output a discharging start command for operating the discharging unit during a period from the time after the power failure detecting unit detects power failure to the time that a DC voltage value detected by the voltage detecting unit becomes equal to or lower than a first threshold, and that outputs the discharging start command for operating the discharging unit when a DC voltage value detected by the voltage detecting unit becomes equal to or lower than the first threshold.

2. The motor control device according to claim 1, wherein the first threshold is set to be equal to or lower than a crest value of an input voltage at the AC side of the rectifier.

3. The motor control device according to claim 1, wherein after the power failure detecting unit detects power failure, the discharging operation determining unit outputs a discharging stop command for stopping operation of the discharging unit when a DC voltage value detected by the voltage detecting unit is higher than the second threshold, which is a value equal to or higher than a first threshold and also equal to or lower than the resistance discharging operation stop level.

4. The motor control device according to claim 1, comprising a threshold setting unit that sets the first threshold in accordance with a motor driving command commanding operation of the motor, or motor output information that is information on the output of the motor operating based on the motor driving command.

5. The motor control device according to claim 4, wherein the threshold setting unit sets the first threshold to be equal to or lower than a crest value of an input voltage on the AC side of the rectifier, when the motor driving command or the motor output information indicates a regenerating state in which the motor regenerates electric power, and

the threshold setting unit sets the first threshold in accordance with magnitude of acceleration indicated by the motor driving command or magnitude of output of the motor indicated by the motor output information and also to be a value lower than the resistance discharging stop level, when the motor driving command or the motor output information indicates a power running state in which the motor consumes electric power.

6. A motor control device comprising:

a rectifier that rectifies AC power supplied from an AC side to output DC power;

an inverter that is connected to a DC link at a DC side of the rectifier, and performs interconversion of electric power between DC power at the DC link and drive power for a motor or regenerative electric power, which are AC power;

a power failure detecting unit that detects power failure at the AC side of the rectifier;

a voltage detecting unit that detects a DC voltage value at the DC link;

an electric storage device that is connected to the DC link, and stores DC power;

a charging unit that has a boosting function of charging the electric storage device at a voltage higher than a DC voltage at the DC link;

a discharging unit that makes short-circuiting between the electric storage device and the DC link to discharge DC power stored in the electric storage device to the DC link;

a resistance discharge device that is connected to the DC link wherein after the power failure detecting unit detects power failure, the resistance discharge device starts resistance discharging operation of consuming DC power of the DC link by resistance discharging when a DC voltage value detected by the voltage detecting unit is equal to or higher than a resistance discharging start level, and the resistance discharge device stops the resistance discharging operation when a DC voltage value detected by the voltage detecting unit is equal to or lower than a resistance discharging stop level lower than the resistance discharging start level; and

a discharging operation determining unit that does not output a discharging start command during a period from the time after the power failure detecting unit detects power failure to the time that a motor driving command commanding power running operation of the motor or motor output information that is information on the output of the motor performing power running operation based on the motor driving command, becomes equal to or higher than a third threshold, and that outputs the discharging start command for operation of the discharging unit when the motor driving command or the motor output information becomes equal to or higher than the third threshold.

7. The motor control device according to claim 6, wherein after the power failure detecting unit detects power failure, the discharging operation determining unit outputs a discharging stop command for stopping operation of the discharging unit when a motor driving command commanding regenerating operation of the motor or motor output information that is information on the output of the motor performing regenerating operation based on the motor driving command, is equal to or lower than a fourth threshold lower than the third threshold.