Apparatus and method for limiting the speed of an electric motor

• US 5,757,161 A
• Filed: 04/21/1997
• Issued: 05/26/1998
• Est. Priority Date: 12/01/1994
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Tamaki, Satoshi, Ikkai, Yasufumi
• Primary Examiner(s): Sircus, Brian
• Application Number:
  US08/845,202
• Time in Patent Office: 400 Days
• Field of Search: 318/711, 318/715, 318/721, 318/722, 318/757-759, 318/798-817, 318/369, 318/375, 318/376, 388/801, 388/803, 388/826-828, 388/830, 180/170-174, 180/178, 180/179
• US Class Current: 318/719
• CPC Class Codes: B60L 15/025 using field orientation; Vector control; Direct Torque Control [DTC]
• CPC Class Codes: B60L 3/00 Electric devices on electrically-propelled vehicles for safety purposes; Monitoring operating variables, e.g. speed, deceleration or energy consumption methods or circuit arrangements for monitoring or controlling batteries or fuel cells B60L58/00
• CPC Class Codes: B60L 7/14 for vehicles propelled by ac motors
• CPC Class Codes: H02H 7/093 against increase beyond, or decrease below, a predetermined level of rotational speed centrifugal switches H01H35/10
• CPC Class Codes: H02P 21/36 Arrangements for braking or slowing; Four quadrant control
• CPC Class Codes: H02P 29/02 Providing protection against overload without automatic interruption of supply protection against faults of stepper motors H02P8/36
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility

Abstract

A motor control apparatus for detecting motor overspeed in an electric car to prevent destruction of the motor and assure the safety of the vehicle. Torque control is applied when the motor speed is less than a specified rotational velocity. When the motor is detected to be operating at greater than the specified rotational velocity, i.e., when motor overspeed is detected, the motor is controlled to coast or regenerate to lower the motor speed to less than the specified rotational velocity, after which normal control is resumed, thereby preventing collision due to sudden braking and preventing damage to the motor.

Claims

1. A motor control apparatus for controlling a rotation speed of a motor for use in an electric car, comprising:

rotation speed detection means for detecting a rotation speed of said motor;

power supplying means for supplying power to said motor; and

speed control means for controlling said rotation speed of said motor by adjusting said power supplying means in response to an input command, said speed control means forcibly making said power supplying means stop supplying power to said motor when said rotation speed of said motor exceeds a predetermined control start speed, whereby said motor coasts irrespective of said input command when said motor speed exceeds said predetermined control start speed, said speed control means permitting said power supplying means to resume supplying power to said motor when said rotation speed of said motor reaches a predetermined control end speed which is lower than said predetermined control start speed, said speed control means comprising a closed-loop control circuit that controls said rotation speed of said motor.

2. A motor control apparatus as claimed in claim 1, further comprising:

weakening current supplying means for supplying a weakening current to said motor, wherein said speed control means sets said weakening current to a predetermined level when said rotation speed exceeds a predetermined speed.

3. A motor control apparatus for controlling a rotation speed of a motor for use in an electric car, comprising:

rotation speed detection means for detecting a rotation speed of said motor;

power supplying means for supplying power to said motor; and

speed control means for controlling said rotation speed of said motor by adjusting said power supplying means in response to an input command, said speed control means forcibly making said power supplying means regenerate power from said motor when said rotation speed of said motor exceeds a predetermined limit speed, whereby said motor regenerates power irrespective of said input command when said motor speed exceeds said limit speed, said speed control means permitting said power supplying means to resume supplying power to said motor when said rotation speed of said motor reaches a predetermined control end speed that is lower than said predetermined limit speed, said speed control means comprising a closed-loop control circuit that controls said rotation speed of said motor.

4. A motor control apparatus as claimed in claim 3, further comprising:

weakening current supplying means for supplying a weakening current to said motor, wherein

said speed control means sets said the weakening current to a predetermined level when said rotation speed exceeds a predetermined speed.

5. A motor control method for controlling a rotation speed of a motor for use in an electric car, comprising:

detecting a rotation speed of the motor;

supplying power, via a power supply, to the motor;

controlling the rotation speed of the motor by adjusting the power supply to the motor in response to an input command, the speed of the motor being controlled by providing a closed-loop control circuit that controls the rotation steed of the motor;

forcibly stopping the power supply from supplying power to the motor when the rotation speed of the motor exceeds a predetermined control start speed, whereby the motor coasts in response to an input command when the motor speed exceeds the control start speed; and

re-enabling the power supply to supply power to the motor when the rotation speed of the motor reaches a predetermined control end speed that is lower than the predetermined control start speed.

6. A motor control method as claimed in claim 5, further comprising the steps of:

supplying a weakening current to the motor; and

setting the weakening current to a predetermined level when the rotation speed exceeds a predetermined speed.

7. A motor control method for controlling a rotation speed of a motor for use in an electric car, comprising:

detecting a rotation speed of the motor;

supplying power, via a power supply, to the motor;

controlling the rotation speed of the motor by adjusting the power supply to the motor in response to an input command, the rotation speed of the motor being controlled by providing a closed-loop control circuit that controls the rotation speed of the motor;

forcibly regenerating power from the motor when the rotation speed of the motor exceeds a predetermined limit speed, whereby the motor regenerates power irrespective of the input command when the motor speed exceeds the predetermined limit speed; and

re-enabling the power supply to supply power to the motor when the rotation speed of the motor reaches a predetermined control end speed that is lower than the predetermined limit speed.

8. A motor control method as claimed in claim 7, further comprising the steps of:

supplying a weakening current to the motor; and

setting the weakening current to a predetermined level when the rotation speed exceeds a predetermined speed.

9. A method for controlling a rotational speed of a motor, comprising the steps of:

supplying power to the motor to effect a rotation of the motor;

detecting and controlling a rotational speed of the motor by providing a closed-loop control circuit that controls the rotation speed of the motor;

setting an operation of the motor to a coast mode when the rotational speed of the motor is detected to reach a predetermined control start speed;

setting the operation of the motor to a constant regeneration mode when the rotational speed of the motor is detected to increase to a predetermined limit speed; and

resuming the supplying of power to the motor when the rotational speed of the motor is detected to fall to a predetermined control end speed.

10. The method of claim 9, wherein the supplying step comprises supplying electrical power to the motor.

11. The method of claim 10, wherein the method for controlling a rotational speed of a motor is used with an electric vehicle.

12. The method of claim 9, wherein the step of setting the operation of the motor to a coast mode comprises the step of supplying a weakening current to the motor to a predetermined level when the rotational speed of the motor reaches the predetermined control start speed.

13. The method of claim 9, wherein the step of setting the operation of the motor to a constant regeneration mode occurs whenever the step of setting the operation of the motor to a coast mode fails to reduce the rotational speed of the motor.

14. The method of claim 9, wherein the predetermined control start speed is less than the predetermined limit speed.