GROUND FAULT INTERRUPT CIRCUIT FOR ELECTRIC VEHICLE

• US 20130119933A1
• Filed: 10/14/2012
• Published: 05/16/2013
• Est. Priority Date: 04/14/2010
• Status: Abandoned Application

• Current Assignee: Aerovironment
• Original Assignee: Albert Flack
• Inventors: FLACK, Albert, BERMAN, Scott
• Application Number:
  US13/651,417
• Publication Number:
  US 20130119933A1
• Time in Patent Office: Days
• US Class Current: 320/109
• 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 3/0069 relating to the isolation, e.g. ground fault or leak current
• CPC Class Codes: H02H 9/08 Limitation or suppression of earth fault currents, e.g. Petersen coil
• CPC Class Codes: H03F 1/3235 using a pilot signal
• CPC Class Codes: H03F 3/45 Differential amplifiers differential sense amplifiers G11C7/062

Abstract

In one implementation, a ground fault interrupt circuit is provided for a utility power connection to an electric vehicle charging unit. The ground fault interrupt circuit may include a gain amplifier having an input connected to be capable of receiving a differential current from a current sensing transformer and a comparator having an input connect to a reference voltage. It includes a rectifier circuit connected between the gain amplifier and the comparator with a charge accumulator circuit coupled between the rectifier and the comparator.

Claims

1. A ground fault interrupt circuit for a utility power connection to an electric vehicle charging unit, the ground fault interrupt circuit comprising:

a) a gain amplifier having an input connected to be capable of receiving a differential current from a current sensing transformer;

b) a filter having an input connected to an output of the gain amplifier;

c) a comparator having an input connected to an output of the half wave rectified dual stage filter;

d) a fault latch having an input connected to the output of the comparator;

e) a contactor control circuit having an input connected to an output of the fault latch; and

f) a utility power line contactor having a contactor control input connected to an output of the contactor control circuit.

2. The circuit of claim 1, wherein the filter is a half wave rectified dual stage filter.

3. The circuit of claim 1, wherein the gain amplifier comprises a surge protection circuit, and further comprising a redundant surge protection circuit connected to an input of the gain amplifier.

4. The circuit of claim 3, wherein the redundant surge protection circuit comprises a pair of diodes connected to lower and upper reference busses.

5. The circuit of claim 1, further comprising a microprocessor connected to the output of the fault latch so as to detect a fault trip, and to a fault latch reset input of the fault latch.

6. The circuit of claim 1, wherein the contactor control circuit further comprises a contactor control relay, the contactor control relay is connected to the utility power line contactor.

7. The circuit of claim 6, further comprising a contactor disable latch responsive to the output of the comparator, the contactor disable latch being connected to an input of the contactor control circuit in parallel with the output of fault latch so as to provide a redundant control signal for controlling the contactor control relay.

8. The circuit of claim 1, further comprising a differential current sensing transformer coupled to utility power lines.

9. A method for electric vehicle charging for detecting a ground fault comprising:

detecting a differential current in utility power supply;

generating a ground fault signal from the detected differential current;

accumulating the ground fault signal over time; and

comparing the accumulated ground fault signal to a threshold voltage; and

causing a ground fault interrupt when the accumulated ground fault signal exceeds the threshold voltage.

10. The method of claim 9, wherein accumulating the ground fault signal over time comprises filtering the ground fault signal.

11. The method of claim 10, wherein filtering the ground fault signal comprises using a double stage filter.

12. The method of claim 11, wherein filtering the ground fault signal comprises using a half wave rectifying double stage filter.

13. The method of claim 9, wherein accumulating the ground fault signal over time comprises accumulating ground fault signals having a voltage level below the threshold voltage so as to cause the ground fault interrupt at the threshold voltage.

14. The method of claim 9, wherein accumulating the ground fault signal over time comprises accumulating multiple discrete signals having a voltage level below the threshold voltage so as to cause the ground fault interrupt at the threshold voltage.

15. The method of claim 14, wherein accumulating the ground fault signal over time and causing the ground fault interrupt comprises causing the ground fault interrupt when the multiple discrete signals have a duration that is less than a duty cycle.

16. The method of claim 9, wherein generating the ground fault signal from the detected differential current comprises using a gain amplifier.

17. The method of claim 9, comprising latching a ground fault interrupt signal when the accumulated ground fault signal exceeds the threshold voltage.

18. The method of claim 9, comprising opening a utility power line contactor when the accumulated ground fault signal exceeds the threshold voltage.

19. The method of claim 9, further comprising generating an inverted ground fault signal, and wherein accumulating further comprises accumulating both the ground fault signal and the inverted ground fault signal over time.

20. The method of claim 19, further comprising rectifying and the ground fault signal and the inverted ground fault signal prior to accumulating.

21. The method of claim 19, wherein generating the ground fault signal comprises generating the ground fault signal about a reference voltage, and wherein generating the inverted ground fault signal comprises generating the ground fault signal about the reference voltage.

22. The method of claim 21, further comprising rectifying and the ground fault signal and the inverted ground fault signal prior to accumulating.

23. A method for electric vehicle charging for detecting a ground fault comprising:

detecting a differential current in utility power supply;

generating a ground fault signal from the detected differential current;

filtering the ground fault signal; and

comparing the filtered ground fault signal to a threshold voltage; and

disconnecting the utility power supply when the filtered ground fault signal exceeds the threshold voltage.

24. The method of claim 23, wherein filtering the ground fault signal comprises using a half wave rectifying double stage filter.

25. The method of claim 23, comprising generating a latched fault signal when the filtered ground fault signal exceeds the threshold voltage.

26. The method of claim 25, comprising opening a utility power contactor to disconnect the utility power supply in response to the latched fault signal.

27. The method of claim 26, wherein generating the latched fault signal comprises generating a ground fault interrupt fault signal and generating a contactor fault disable signal, and further comprising opening the utility power contactor in response to either the ground fault interrupt fault signal or the contactor fault disable signal.

28. A ground fault interrupt circuit for a utility power connection to an electric vehicle charging unit, the ground fault interrupt circuit comprising:

a) a gain amplifier having an input connected to be capable of receiving a differential current from a current sensing transformer;

b) a comparator having an input connect to a reference voltage;

c) a rectifier circuit connected between the gain amplifier and the comparator; and

d) a charge accumulator circuit coupled between the rectifier and the comparator.

29. The circuit of claim 28 further comprising an inverter connected between the gain amplifier and the rectifier circuit.

30. The circuit of claim 28, further comprising an inverter having an input connected to an output of the gain amplifier, and wherein the rectifier circuit is a full wave rectifier circuit connected to the output of the gain amplifier and to an output of the inverter, and wherein an output of the full wave rectifier circuit is connected to the charge accumulator circuit.

31. The circuit of claim 28, wherein the charge accumulator comprises the rectifier circuit, and wherein the rectifier circuit is a half wave rectifier circuit connected to the gain amplifier.

32. The circuit of claim 28 further comprising an EMI protection circuit at an input of the ground fault interrupt circuit.

33. The circuit of claim 32 wherein the EMI protection circuit comprises an inductor and a resistor connected in series, and at least one capacitor connected across the differential input and to ground.

34. The circuit of claim 28 further comprising a fault latch having an input connected to an output of the comparator.

35. The circuit of claim 34 further comprising a contactor control circuit having an input connected to an output of the fault latch.

36. The circuit of claim 35, further comprising a utility power line contactor having a contactor control input.

37. The circuit of claim 36 further comprising an inverter having an input connected to an output of the gain amplifier, and wherein the rectifier circuit is a full wave rectifier circuit connected to the output of the gain amplifier and to an output of the inverter, and wherein an output of the full wave rectifier circuit is connected to the charge accumulator circuit.

38. The circuit of claim 36, wherein the charge accumulator comprises the rectifier circuit, and wherein the rectifier circuit is a half wave rectifier circuit connected to the gain amplifier.