Power converter

• US 8,688,301 B2
• Filed: 06/28/2007
• Issued: 04/01/2014
• Est. Priority Date: 06/28/2007
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Kitanaka, Hidetoshi
• Primary Examiner(s): To, Tuan C.
• Assistant Examiner(s): Kan, Yuri
• Application Number:
  US12/598,435
• Publication Number:
  US 20100076638A1
• Time in Patent Office: 2,469 Days
• Field of Search: 701/22, 361/30, 361/31, 361/71, 361/93.1, 318/139, 318/400.15, 318/400.21, 318/490, 318/432, 318/716, 318/760, 318/721, 318/727, 318/101, 369/226, 388/804, 180/65.1, 290/1.R, 440/84, 320/101, 363/95
• US Class Current: 701/22
• CPC Class Codes: B60L 2200/26 Rail vehicles
• CPC Class Codes: B60L 3/003 relating to inverters
• CPC Class Codes: B60L 3/0061 relating to electrical machines
• CPC Class Codes: H02P 27/06 using dc to ac converters or inverters H02P27/05 takes precedence
• CPC Class Codes: H02P 29/0241 the fault being an overvoltage
• CPC Class Codes: H02P 29/0243 the fault being a broken phase
• CPC Class Codes: H02P 29/027 the fault being an over-current
• CPC Class Codes: H02P 29/032 Preventing damage to the motor, e.g. setting individual current limits for different drive conditions
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility

Abstract

In a power converter a controller determines that an AC motor is in an abnormal state when a voltage of each phase of the AC motor detected by a voltage detector is in an unbalanced state where the voltage exceeds a predetermined value, and turns an opening/closing unit OFF to prevent damage generated in the AC motor from becoming worse. Moreover, the controller determines abnormality of the opening/closing unit based on a current of each phase detected by a current detector, and the controller performs control to reduce the number of revolutions of the AC motor upon determining that at least one of the AC motor and the opening/closing unit is in an abnormal state.

Claims

1. A power converter comprising:

an inverter that converts a DC voltage or an AC voltage to an AC voltage of an arbitrary frequency to drive an AC motor having a permanent magnet therein;

an opening/closing unit that is connected between the inverter and the AC motor;

a controller that controls the inverter and the opening/closing unit;

a voltage detector provided between the opening/closing unit and the AC motor; and

a current detector provided between the inverter and the opening/closing unit, wherein when the inverter is turned OFF, the controller compares an induced voltage in a state where the inverter is turned OFF with an induced voltage in a normal state to detect abnormality of the AC motor,

wherein when the AC motor is in an abnormal state, the controller turns OFF the opening/closing unit, and

wherein when a current larger than a predetermined threshold value is still detected by the current detector even though the opening/closing unit is turned OFF, the controller determines that the opening/closing unit is in an abnormal state or the current is excessive as compared with an interruption capacity of the opening/closing unit, and performs a predetermined procedure to reduce a number of revolutions of the AC motor.

2. The power converter according to claim 1, wherein the controller includes a logic circuit that controls the opening/closing unit to be turned OFF even if there was an ON-request of the opening/closing unit upon determining that the AC motor is in an abnormal state, to prohibit the opening/closing unit from closing again.

3. The power converter according to claim 1, wherein the controller determines that the AC motor is in an abnormal state if a difference between phase voltages of the AC motor detected by the voltage detector exceeds a predetermined value.

4. The power converter according to claim 1, wherein the predetermined procedure includes an operation of outputting a control signal for decelerating an electric vehicle provided with the power converter.

5. The power converter according to claim 1, wherein the predetermined procedure includes an operation for outputting a control signal for applying a brake to an electric vehicle provided with the power converter.

6. The power converter according to claim 1, wherein the predetermined procedure includes an operation for outputting a control signal for turning OFF power running of an electric vehicle provided with the power converter.

7. A power converter comprising:

an inverter that converts a DC voltage or an AC voltage to an AC voltage of an arbitrary frequency to drive an AC motor having a permanent magnet therein;

an opening/closing unit that is connected between the inverter and the AC motor;

a voltage detector provided between the opening/closing unit and the AC motor;

a controller that controls the inverter and the opening/closing unit, and

a current detector provided between the inverter and the opening/closing unit, wherein when the inverter is turned OFF, the controller compares an induced voltage in a state where the inverter is turned OFF with an induced voltage in a normal state to detect abnormality of the AC motor,

wherein when the AC motor is in an abnormal state, the controller turns OFF the opening/closing unit, and

wherein when an abnormal induced voltage is still detected by the voltage detector even though the opening/closing unit is turned OFF, the controller determines that there is a possibility that an interphase short circuit or ground fault occurs in a part of a stator coil of the AC motor, and performs a predetermined procedure to reduce a number of revolutions of the AC motor.

8. The power converter according to claim 7, wherein the controller includes a logic circuit that controls the opening/closing unit to be turned OFF even if there was an ON-request of the opening/closing unit upon determining that the AC motor is in an abnormal state, to prohibit the opening/closing unit from closing again.

9. The power converter according to claim 7, wherein the controller determines that the AC motor is in an abnormal state if a difference between phase voltages of the AC motor detected by the voltage detector exceeds a predetermined value.

10. The power converter according to claim 7, wherein the predetermined procedure includes an operation of outputting a control signal for decelerating an electric vehicle provided with the power converter.

11. The power converter according to claim 7, wherein the predetermined procedure includes an operation for outputting a control signal for applying a brake to an electric vehicle provided with the power converter.

12. The power converter according to claim 7, wherein the predetermined procedure includes an operation for outputting a control signal for turning OFF power running of an electric vehicle provided with the power converter OFF.