AC Motor Controller

• US 20090059446A1
• Filed: 04/15/2005
• Published: 03/05/2009
• Est. Priority Date: 04/15/2005
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yoshihara, Shigeyuki, Matsui, Hirokazu, Sawada, Takefumi
• Granted Patent: US 7,759,888 B2
• Time in Patent Office: Days
• US Class Current: 361/31
• CPC Class Codes: G01R 31/343 in operation
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: H02H 7/0805 for synchronous motors
• CPC Class Codes: H02P 29/0241 the fault being an overvoltage

Abstract

There is provided an AC motor controller capable of detecting an abnormal state of a motor cable while an AC motor is operating without using a special circuit but using a processor.

The AC motor controller includes an AC motor; an inverter for driving the AC motor with a motor current through a motor cable; and a motor current detector for detecting the motor current flowing in the motor cable of the AC motor, in which a processor detects an abnormal state of the motor cable such as an inter-phase short circuit and an open circuit based on the motor current detected by the motor current detector.

Claims

1. An AC motor controller, comprising:

an AC motor;

an inverter for driving the AC motor with three phase motor currents each through a motor cable;

a motor current detector for detecting the three phase motor currents each flowing in the motor cable connected to the AC motor; and

a processor for detecting the occurrence of an abnormal state of the motor cable based on the three phase motor currents detected by the motor current detector, the processor identifying the phase of the motor cable in which the abnormal state occurs.

2. The AC motor controller according to claim 1, wherein the abnormal state of the motor cable is an inter-phase short circuit state;

the abnormal state is determined based on the amplitude of the motor current; and

the processor detects the abnormal state while the motor is operating.

3. The AC motor controller according to claim 2, wherein the motor current detector determines whether or not the inter-phase short circuit state exists by substantially simultaneously sampling two of the three phase currents.

5. The AC motor controller according to claim 3, wherein if a condition that the substantially simultaneously sampled two phase currents are greater than a predetermined value continues for a predetermined time period, the two phase motor cables are determined to be in the inter-phase short circuit state.

6. The AC motor controller according to claim 5, wherein the three phases are a U phase, a V phase and a W phase;

and the determination whether or not the inter-phase short circuit state exists is made for all inter-phases;

between the U phase and V phase, between the V phase and W phase, and between the W phase and U phase.

7. The AC motor controller according to claim 2, wherein the AC motor controller detects the inter-phase short circuit state by comparing the motor current detected at the motor current detector with a current command value in the controller.

8. The AC motor controller according to claim 1, wherein the abnormal state of the motor cable is a disconnected or unconnected state;

and the processor detects the abnormal state while the motor is operating.

9. The AC motor controller according to claim 1, wherein the processor controls the AC motor.

10. The AC motor controller according to claim 1, further comprising a second processor other than the processor for detecting the abnormal state of the motor cable, wherein the second processor controls the AC motor.

4. (canceled)

11. An AC motor controller, comprising:

an AC motor driven by a plurality of motor currents;

an inverter for driving the AC motor with the plurality of motor currents through a plurality of motor cables;

a motor current detector for detecting the plurality of motor currents each flowing in a corresponding one of the plurality of motor cables connected to the AC motor;

storage means for storing the plurality of motor currents detected by the motor current detector; and

a processor for comparing the plurality of motor currents stored by the storage means with a predetermined value and, if at least two of the plurality of motor currents are greater than the predetermined value, determining that an inter-phase short circuit state exists between the motor cables, the processor identifying the phases of the motor cables in the inter-phase short circuit state.

12. The AC motor controller according to claim 11, wherein the plurality of motor currents are a U phase current, a V phase current and a W phase current;

and the abnormal state is an inter-phase short circuit state between the motor cables; and

the processor detects the abnormal state while the motor is operating.

13. The AC motor controller according to claim 12, wherein the AC motor controller uses software to detect the abnormal state.

14. An AC motor controller, comprising:

an AC motor driven by a plurality of motor currents;

an inverter for driving the AC motor with the plurality of motor currents through a plurality of motor cables;

a motor current detector for detecting the plurality of motor currents each flowing in a corresponding one of the plurality of motor cables connected to the AC motor;

storage means for storing the plurality of motor currents detected by the motor current detector; and

a processor for comparing the motor currents stored by the storage means with a predetermined value and, if at least one of the plurality of motor currents are less than the predetermined value, determining that an open circuit state exists in at least one of the motor cables, the processor identifying the phase of the motor cables in which the open circuit state exists.

15. The AC motor controller according to claim 14, wherein the plurality of motor currents are a U phase current, a V phase current and a W phase current;

and the abnormal state is an open circuit state in the motor cables; and

the processor detects the abnormal state while the motor is operating.

16. The AC motor controller according to claim 15, wherein the AC motor controller uses software to detect the abnormal state.