Method and apparatus for power generation failure diagnostics

• US 20100066551A1
• Filed: 09/15/2008
• Published: 03/18/2010
• Est. Priority Date: 09/15/2008
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Hendrickson, Mathew, Beach, Frederick, Bailey, Bradley
• Granted Patent: US 7,956,762 B2
• Time in Patent Office: Days
• US Class Current: 340/648
• CPC Class Codes: G01R 31/343 in operation

Abstract

A controller (500) in an electric drive system is used to develop power generation failure diagnostics. During operation, the controller (500) receives a set of generator inputs, a set of machine parameters, and a set of diagnostic values. Next, the controller (500) determines a set of expected operating values corresponding to the set of diagnostic values. The controller (500) then compares the obtained diagnostic values to one or more corresponding expected operating values. If the difference is greater than a threshold, the controller (500) provides an appropriate fault indication.

Claims

1. A method for diagnosing a power generation failure for a power circuit in an electric drive coupled with a prime mover, the power circuit including a rectifier circuit coupled with a power generator and disposed to provide a DC output voltage across a DC link, the method comprising:

receiving at least one power generator input;

receiving at least one machine parameter associated with the prime mover;

receiving a set of diagnostic values associated with the DC link and the at least one power generator input;

determining a set of expected operating values based on the at least one power generator input and the at least one machine parameter, the set of expected operating values corresponding to the received set of diagnostic values;

comparing each diagnostic value from the set of diagnostic values to a corresponding expected operating value from the set of expected operating values to determine a difference for each diagnostic value; and

setting an indicator flag that a power generation failure exists if the difference between one or more diagnostic values and a corresponding one or more expected values exceeds a threshold.

2. The method of claim 1, wherein the power generator is a multi-phase alternating current (AC) synchronous generator having a rotating input coupled with a prime mover output, an input winding disposed to receive an excitation signal as the at least one power generator input, an output winding magnetically coupled with the input winding and disposed to provide a set of alternator phase currents to the rectifier circuit, wherein each phase current comprises one of the diagnostic values associated with the DC link.

3. The method of claim 2, wherein the at least one machine parameter includes a prime mover output speed.

4. The method of claim 3, wherein the set of diagnostic values associated with the DC link includes a DC link voltage developed across the DC link.

5. The method of claim 4 wherein the diagnostic flag is set when the DC link voltage is less than an expected DC link voltage and the alternator phase current is less than an expected alternator phase current.

6. The method of claim 5 further including the step of providing an alert in response to setting the indicator flag that specifies the short circuit condition.

7. The method of claim 5, further comprising setting a second indicator flag if the DC link voltage is less than an expected DC link voltage and the alternator phase current is about the same as an expected alternator phase current.

8. The method of claim 6 wherein the step of providing the alert includes activating a visual indicator.

9. A controller disposed to monitor whether a power generation failure has occurred in a power circuit of an electric drive system in a machine that includes a prime mover disposed to provide an output to a power generator, a rectifier circuit coupled with the output of the power generator, and a direct current (DC) link disposed in circuit with the rectifier, the controller comprising:

an input receiving portion configured to receive a set of diagnostic values relating to engine parameters associated with the prime mover, a set of diagnostic values associated with the power generator inputs, and a set of diagnostic values associated with the DC link;

a determination portion configured to determine, based on the set of power generator inputs and the set of machine parameters, a set of expected operating values corresponding to the set of diagnostic value;

a comparison portion configured to compare each of the diagnostic values for the set of diagnostic values to a corresponding expected operating value from the set of expected operating values to determine a set of differences;

a logic portion configured to determine whether a power generation failure condition has occurred based on the set of differences; and

an indicator portion configured to set a flag when the power generation failure has been determined.

10. The controller of claim 9, wherein the power generator is a multi-phase alternating current (AC) synchronous generator having a rotating input coupled with a prime mover output, an input winding disposed to receive an excitation signal, an output winding magnetically coupled with the input winding and disposed to provide a set of alternator phase currents to the rectifier circuit, wherein each phase current from the set of alternator phase currents is associated with a different phase value.

11. The controller apparatus of claim 10, wherein the set of diagnostic values relating to engine parameters associated with the engine includes a prime mover output speed.

12. The controller apparatus of claim 11, wherein the set of diagnostic values associated with the power generator inputs includes an excitation value developed at the power generator input winding.

13. The controller apparatus of claim 12, wherein the set of diagnostic values associated with the DC link includes a DC link voltage developed across the DC link.

14. The controller of claim 13, wherein the logic portion is configured to indicate a power generation failure when the DC link voltage developed across the DC link is less than an expected DC link voltage and at least one of the alternator phase currents is less than an expected alternator phase current.

15. The controller of claim 9, wherein the logic portion is further configured to set a second indicator flag if the DC link voltage developed across the DC link is less than an expected DC link voltage and at least one of the alternator phase currents is about the same as an expected alternator phase current.

16. The controller of claim 9, further including an alert portion responsive to the indicator portion and being configured to activate a visual indicator associated with the controller when the power generation failure condition has been determined.

17. A system including a power generator associated with an electric drive system in a machine including a prime mover disposed to provide an output coupled with the power generator, the system comprising:

a rectifier circuit coupled to an output of the power generator;

a DC link coupled to the rectifier circuit having a DC link voltage defined between a first DC rail and a second DC rail; and

a controller configured to receive a set of generator inputs, a set of machine parameters associated with the machine, and a set of diagnostic values associated with the power generator and the DC link, the controller being further configured to determine a set of expected operating values for the power generator and of the DC link, to compare the set of diagnostic values with the set of expected values, and to set a flag indicating a power generation failure condition when the comparison exceeds a threshold.

18. The system of claim 17, wherein the power generator is a multi-phase alternating current (AC) synchronous generator having a input coupled with the output of the prime mover, an input winding disposed at least one of the set of diagnostic values associated with the generator, an output winding magnetically coupled with the input winding and disposed to provide a set of alternator phase currents to the rectifier circuit, wherein the set of diagnostic values associated with the generator includes the set of alternator phase currents.

19. The system of claim 18, wherein the set of machine parameters includes a prime mover output speed.

20. The system of claim 17 further comprising:

an inverter circuit coupled with the DC link;

an output drive coupled with the inverter circuit; and

a retard circuit coupled with the DC link, the inverter circuit, and the output drive and disposed to dissipate retard energy supplied by the output drive through the inverter circuit during a retard mode of operation.