Motor drive apparatus having power failure detection unit for determining presence or absence of power failure

• US 8,664,897 B2
• Filed: 09/13/2012
• Issued: 03/04/2014
• Est. Priority Date: 11/30/2011
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: Iwashita, Yasusuke, Okita, Tadashi, Niwa, Masakazu
• Primary Examiner(s): Ro, Bentsu
• Assistant Examiner(s): LUO, DAVID S
• Application Number:
  US13/612,975
• Publication Number:
  US 20130134910A1
• Time in Patent Office: 537 Days
• Field of Search: 318/376, 318/375, 318/362
• US Class Current: 318/376
• CPC Class Codes: B29C 2045/7673 Recovering energy or power from drive motors
• CPC Class Codes: B29C 45/7666 of power or energy, e.g. integral function of force
• CPC Class Codes: H02P 27/06 using dc to ac converters or inverters H02P27/05 takes precedence
• CPC Class Codes: H02P 3/14 by regenerative braking
• CPC Class Codes: H02P 5/74 controlling two or more ac dynamo-electric motors H02P5/46, H02P5/60 take precedence
• CPC Class Codes: Y02P 70/10 Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working

Abstract

A motor drive apparatus includes a rectifier which converts AC power to DC power and DC power to AC power, an inverter which converts the DC power output by the rectifier to AC power and supplies the AC power to a motor, and which converts regenerative power from the motor to DC power and returns the DC power to the rectifier, a DC voltage detection unit which detects a DC output voltage of the rectifier, an AC voltage detection unit which detects an AC output voltage of the rectifier, a frequency calculation unit which calculates the frequency of the AC voltage; a storage unit which stores as a reference value the DC voltage at the start of the regenerative operation, and a power failure detection unit which determines the presence or absence of a power failure by using the DC voltage, the reference value, and the AC voltage frequency.

Claims

1. A motor drive apparatus a 120-degree conduction mode rectifier which, during powering operation, converts AC power supplied from an AC side to DC power for output and, during regenerative operation, converts DC power supplied from a DC side to AC power for output;

an inverter which, during powering operation, converts the DC power output by the 120-degree conduction mode rectifier to AC power and supplies the AC power as drive power to a motor, and which, during regenerative operation, converts regenerative AC power recovered from the motor to DC power and returns the DC power to the 120-degree conduction mode rectifier;

a DC voltage detection unit which detects a DC voltage on the DC output side of the 120-degree conduction mode rectifier;

an AC voltage detection unit which detects an AC voltage on the AC output side of the 120-degree conduction mode rectifier;

a frequency calculation unit which calculates the frequency of the AC voltage detected by the AE voltage detection unit;

a storage unit which stores as a reference value the DC voltage detected by the DC voltage detection unit at the start of the regenerative operation of the 120-degree conduction mode rectifier; and

a power failure detection unit which the AC side of the 120-degree conduction mode rectifier during the regenerative operation of the 120-degree conduction mode rectifier, by using the DC voltage detected by the DC voltage detection unit, the reference frequency calculated by the frequency calculation unit,

wherein the power failure detection unit includes;

a voltage evaluation unit which determines whether the DC voltage detected by the DC voltage detection unit during the regenerative operation of the 120-degree conduction mode rectifier is larger than the reference value; and

a frequency abnormality detection unit calculated by the frequency calculation unit is outside a normal frequency range when it is determined by the voltage evaluation unit that the DC voltage detected by the DC voltage detection unit during the regenerative operation of the 120-degree conduction mode rectifier is larger than the reference value, and wherein

when the frequency abnormality detection unit has detected that the AC voltage frequency calculated by the frequency calculation unit has been outside the normal frequency range continuously for a predetermined period of time, the power failure detection

unit determines that a power failure has occurred on the AC side of the 120-degree conduction mode rectifier.

2. The motor drive apparatus according to claim 1, wherein the normal frequency range is a range of frequencies centered about the frequency calculated by the frequency calculation unit at the start of the regenerative operation of the 120-degree conduction mode rectifier.

3. A motor drive apparatus comprising:

a 120-degree conduction mode rectifier which, during powering operation, converts AC power supplied from an AC side to DC power for output and, during regenerative operation, converts DC power supplied from a DC side to AC power for output;

an inverter which, during powering operation, converts the DC power output by the 120-degree conduction mode rectifier to AC power and supplies the AC power as drive power to a motor, and which, during regenerative operation, converts regenerative AC power recovered from the motor to DC power and returns the DC power to the 120-degree conduction mode rectifier;

a DC voltage detection unit which detects a DC voltage on the DC output side of the 120-degree conduction mode rectifier;

an AC voltage detection unit which detects an AC voltage on the AC output side of the 120-degree conduction mode rectifier;

a frequency calculation unit which calculates the frequency of the AE voltage detected b the AC voltage detection unit;

a storage unit which stores as a reference value the DC voltage detected by the DC voltage detection unit at the start of the regenerative operation of the 120-degree conduction mode rectifier;

a power failure detection unit which determines the presence or absence of a power failure on the AC side of the 120-degree conduction mode rectifier during the regenerative operation of the 120-degree conduction mode rectifier, by using the DC voltage detected by the DC voltage detection unit, the reference value stored in the storage unit, and the AC voltage frequency calculated by the frequency calculation unit; and

an amplitude calculation unit which calculates the amplitude of the AC voltage detected b the AC voltage detection unit,

wherein the power failure detection unit includes;

a voltage evaluation unit which determines whether the DC voltage detected by the DC voltage detection unit during the regenerative operation of the 120-degree conduction mode rectifier is larger than the reference value;

a frequency abnormality detection unit which determines whether the AC voltage frequency calculated by the frequency calculation unit is outside the normal frequency range when it is determined by the voltage evaluation unit that the DC voltage detected by the DC voltage detection unit during the regenerative operation of the 120-degree conduction mode rectifier is larger than the reference value;

a regeneration stopping unit which causes the DC-to-AC power conversion operation of the 120-degree conduction mode rectifier to stop when the frequency abnormality detection unit has detected that the AC voltage frequency calculated by the frequency calculation unit has been outside the normal frequency range continuously for predetermined period of time; and

an amplitude evaluation unit which detects whether or not the AC voltage amplitude calculated by the amplitude calculation unit is equal to or smaller than a predetermined value, and wherein

after the conversion operation of the 120-degree conduction mode rectifier has been caused to stop by the regeneration stopping unit, when the amplitude evaluation unit has detected that the AC voltage amplitude calculated by the amplitude calculation unit is equal to or smaller than the predetermined value, the power failure detection unit determines that a power failure has occurred on the AC side of the 120-degree conduction mode rectifier.

4. The motor drive apparatus according to claim 3, wherein the normal frequency range is a range of frequencies centered about the frequency calculated by the frequency calculation unit at the start of the regenerative operation of the 120-degree conduction mode rectifier.