System and method for detecting a motor shorting relay failure

1. A method for determining a motor shorting relay failure in a motor, the motor having first phase winding in a first leg of the motor, a second phase winding in a second leg of the motor, and a third phase winding in a third leg of the motor, the method comprising:

applying a first voltage signal to the first leg;

applying a second voltage signal to the second leg;

applying a test voltage to a test circuit electrically coupled to the third leg;

measuring a third voltage signal in the third leg at a first predetermined time in response to the application of the first and second voltage signals; and

determining a motor shorting relay failure in the motor, based on the amplitude of the third voltage signal.

2. The method as claimed in claim 1 further comprising measuring the third voltage signal at a second predetermined time.

3. The method as claimed in claim 2 further comprising determining that there is no short in a motor relay in response to the third signal being above a voltage threshold.

4. The method as claimed in claim 3 further comprising determining that there is no open leg in response to the third voltage signal below the voltage threshold.

5. The method as claimed in claim 1 wherein determining the motor shorting relay failure in the motor comprises determining a decay of the third voltage signal.

6. The method as claimed in claim 5 wherein the decay of the third voltage signal to 0 volts determines a motor condition.

7. The method as claimed in claim 6 wherein the motor condition comprises as least one of: a motor relay in a closed condition; a short in the motor; and a short across a relay in the motor.

8. The method as claimed in claim 1 wherein the first voltage signal is applied to a gate of a transistor in the first leg.

9. The method as claimed in claim 8 wherein the second voltage signal is applied to a gate of a transistor in the second leg.

10. The method as claimed in claim 9 further comprising:

removing the first voltage from the first leg;

applying the first voltage signal to the second leg;

applying the second voltage signal to the third leg;

applying a test voltage to a test circuit electrically coupled to the first leg;

measuring a fourth voltage signal in the first leg at a first predetermined time in response to the application of the first and second voltage signals; and

determining a motor shorting relay failure in the motor, based on the amplitude of the fourth voltage signal.

11. The method as claimed in claim 10 further comprising:

removing the first voltage from the second leg;

applying the first voltage signal to the first leg;

applying the second voltage signal to the third leg;

applying a test voltage to a test circuit electrically coupled to the second leg;

measuring a fifth voltage signal in the second leg at a first predetermined time in response to the application of the first and second voltage signals; and

determining a motor shorting relay failure in the motor, based on the amplitude of the fifth voltage signal.

12. A system for determining a motor shorting relay failure in a motor, the motor having first phase winding in a first leg of the motor, a second phase winding in a second leg of the motor, and a third phase winding in a third leg of the motor, the system comprising:

a motor circuit having three legs, each of the legs having a drive circuit transistor arrangement, each arrangement being electrically coupled to a respective phase winding;

a test circuit electrically coupled to each of the drive circuit test arrangements; and

a voltage measurement node electrically coupled to each of the drive circuit transistor arrangements,

a processor electrically coupled to the motor circuit, the processor configured to induce the motor circuit to apply a first voltage signal to the first leg and a second voltage signal to the second leg, to induce the test circuit in the third leg to induce a test voltage to the third leg, and to measure a response voltage from the third leg.

13. The system as claimed in claim 12 wherein the processor is further configured to determine a decay of the response voltage.

14. The system as claimed in claim 13 wherein the processor is further configured to determine a reason for the decay of the response voltage to 0 volts.

15. The system as claimed in claim 14 wherein the reason for the decay of the response voltage to 0 volts is a predetermined condition of a motor relay that controls the operational states of electrical contacts in the motor circuit.

16. The system as claimed in claim 15 wherein the predetermined condition includes at least one of: the motor relay in a closed condition; a short in the motor; and a short across the motor relay in the motor.

17. A computer-readable medium having computer-executable instructions for performing a method comprising:

applying a gate voltage signal to a transistor in a first leg of a drive circuit electrically coupled to a motor circuit;

applying a gate voltage signal to a transistor in a second leg of the drive circuit;

applying a test voltage to a test circuit electrically coupled to a third leg of the drive circuit;

measuring a response voltage from the third leg; and

determining the presence of a motor shorting relay failure in the motor circuit in response to the response voltage.