Granted Patent B2

US 7,112,941 · App. 10/955,127 · Granted Sep 26, 2006

Abstract

Claims (23)

1. A system for protecting a motor against overuse, the system comprising:

a controller for controlling a voltage applied to the motor; and

means for determining an estimated temperature of the motor based on an ambient temperature, a current applied to the motor, a period of time during which the current is applied to the motor, and at least one thermal property, wherein the determining means provides a signal for use by the motor controller to reduce the voltage applied to the motor when the estimated motor temperature is greater than a safe operating temperature of the motor and provides a signal for use by the motor controller to increase the voltage applied to the motor when the estimated motor temperature returns to a level no greater than the safe operating temperature of the motor.

2. The system of claim 1 wherein the means for determining an estimated temperature of the motor comprises a microprocessor.

3. The system of claim 1 wherein the means for determining an estimated temperature of the motor comprises an algorithm.

4. A method for protecting a motor against overuse, the method comprising:

determining an estimated temperature of the motor based on an ambient temperature, a current applied to the motor, a period of time during which the current is applied to the motor, and at least one thermal property, the estimated motor temperature for use in reducing a voltage applied to the motor when the estimated motor temperature is greater than a safe operating temperature of the motor and for use in increasing the voltage applied to the motor when the estimated motor temperature returns to a level no greater than the safe operating temperature of the motor.

5. The method of claim 4 wherein the estimated motor temperature is for use in increasing the voltage applied to the motor when the estimated motor temperature returns to a level no greater than the safe operating temperature of the motor.

6. The method of claim 4 wherein the ambient temperature comprises a measured temperature.

7. The method of claim 4 wherein the motor current comprises a measured current.

8. The method of claim 4 wherein the motor current is zero.

9. The method of claim 4 wherein the at least one thermal property comprise at least one thermal property of the motor.

10. A device for protecting a motor against overuse, the device comprising:

an estimator for determining an estimated temperature of the motor based on an ambient temperature, a current applied to the motor, a period of time during which the current is applied to the motor, and at least one thermal property, wherein the estimator provides a signal for use in reducing the voltage applied to the motor when the estimated motor temperature is greater than a safe operating temperature of the motor; and wherein the estimator provides a signal for use in increasing the voltage applied to the motor when the estimated motor temperature returns to a level no greater than the safe operating temperature of the motor.

11. The device of claim 10 wherein the ambient temperature comprises a measured temperature.

12. The device of claim 10 wherein the motor current comprises a measured current.

13. The device of claim 10 wherein the motor current is zero.

14. The device of claim 10 wherein the at least one thermal property comprise at least one thermal property of the motor.

15. The device of claim 10 wherein the at least one thermal property comprises at least one thermal property of the motor and a motor controller.

16. The device of claim 10 wherein the estimator comprises a microprocessor.

17. The device of claim 10 wherein the estimator comprises an algorithm.

18. The device of claim 10 wherein the estimator and a motor controller are integrated.

19. The device of claim 10 wherein the motor and a motor controller are integrated.

Assignments (10)