Protection of a generator without measuring temperature

• US 20030042876A1
• Filed: 08/12/2002
• Published: 03/06/2003
• Est. Priority Date: 09/06/2001
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Ikeda, Sadafumi
• Granted Patent: US 7,071,658 B2
• Time in Patent Office: Days
• US Class Current: 322/37
• CPC Class Codes: H02P 9/006 Means for protecting the generator by using control control effected upon generator excitation circuit to reduce harmful effects of overloads or transients H02P9/10

Abstract

A method and an apparatus for providing protection to a generator are disclosed. A reference is determined out of rated capability of the generator. Based on the reference, and field current and output conditions of the generator, there is determined a drop in generator performance due to a temperature condition of the generator. Accounting for the drop in generator performance, operation of the generator may be modified to a generator output limit mode.

Claims

1. An apparatus for providing protection to a generator, comprising:

a reference determining block having as inputs, a generator speed of the generator and a generator field current thereof, and determining out of rated capability of the generator, a reference in terms of the magnitude of generator output current; and

a generator performance drop monitoring block receiving the determined reference and a measure of generator output current, calculating a difference between the determined reference and the measure, and outputting a drop in generator performance due to a temperature condition of the generator.

2. The apparatus as claimed in claim 1, wherein the apparatus is operable with a generator drivingly coupled with an internal combustion engine.

3. The apparatus as claimed in claim 2, further comprising means for determining the generator speed by multiplying a measure of engine speed of the engine by a speed ratio between the engine and the generator.

4. The apparatus as claimed in claim 1, wherein the reference determining block determines the reference by table look up using the generator speed and the generator field current.

5. The apparatus as claimed in claim 1, further comprising algorithm to limit operation of the generator in response to the drop in generator performance such that operation of the generator is limited till achievement of a predetermined release criterion.

6. An apparatus for providing protection to a generator, comprising:

a reference determining block having as inputs, a measure of generator output voltage of the generator and a duty ratio of a power transistor of a field current circuit of the generator and determines a reference out of rated capability of the generator in terms of, the magnitude of generator field current; and

a generator performance monitoring block receiving the reference and a measure of generator field current of the generator, calculating a ratio between the reference and the measure, and outputting a drop in generator performance due to a temperature condition of the generator.

7. The apparatus as claimed in claim 6, further comprising algorithm to limit operation of the generator in response to the drop in generator performance such that operation of the generator is limited till achievement of a predetermined release criterion.

8. A method for providing protection to a generator, comprising:

determining a reference out of rated capability of the generator;

determining, based on the reference, and generator field current and output conditions of the generator, a drop in generator performance due to a temperature condition of the generator; and

modifying operation of the generator to a generator output limit mode, accounting for the determined drop in generator performance.

9. The method as claimed in claim 8, further comprising measuring a generator output current of the generator to monitor the output condition of the generator.

10. The method as claimed in claim 9, further comprising determining a generator speed of the generator

11. The method as claimed in claim 10, wherein the determining a reference out of rated capability of the generator includes determining the magnitude of the generator output current as a function of the generator speed and the generator field current and setting the reference to the determined magnitude of the generator output current.

12. The method as claimed in claim 11, wherein the determining a generator speed of the generator includes monitoring an engine speed of an engine drivingly coupled to the generator and multiplying the monitored engine speed by a speed ratio between the engine and the generator.

13. The method as claimed in claim 12, wherein the determining the magnitude of generator output current as a function of the generator speed and the generator field current includes table look up to find the magnitude of the generator output current for the generator speed and the generator field current.

14. The method as claimed in claim 13, wherein the modifying operation of the generator includes lowering the field current till achievement of a predetermined release criterion.

15. The method as claimed in claim 14, wherein the determining a drop in generator performance includes calculating a difference between the generator output current and the reference.

16. The method as claimed in claim 8, further comprising measuring a generator output voltage to monitor the output condition of the generator.

17. The method as claimed in claim 16, further comprising monitoring duty ratio of a transistor of a field current circuit provided for regulating field current in the generator.

18. The method as claimed in claim 17, wherein the determining a reference out of rated capability of the generator includes determining the magnitude of the generator field current as a function of the generator output voltage and the monitored duty ratio and setting the reference to the determined magnitude of the generator field current.

19. The method as claimed in claim 18, wherein the modifying operation of the generator includes lowering the generator field current till achievement of a predetermined release criterion.

20. The method as claimed in claim 19, wherein the determining a drop in generator performance includes calculating a ratio between the measured field current and the reference.

21. An apparatus for providing protection to a generator, comprising:

means for determining a reference out of rated capability of the generator;

means for determining, based on the reference, and generator field current and output conditions of the generator, a drop in generator performance due to a temperature condition of the generator; and

means for modifying operation of the generator to a generator output limit mode, accounting for the determined drop in generator performance.

22. The apparatus as claimed in claim 21, wherein the output condition of the generator is monitored by a measure of a generator output current of the generator.

23. The apparatus as claimed in claim 22, wherein the apparatus is operable with a generator drivingly coupled with an internal combustion engine.

24. The apparatus as claimed in claim 23, further comprising means for receiving an engine speed of the engine and means for multiplying the engine speed by a speed ratio between the engine and the generator.

25. The apparatus as claimed in claim 24, wherein the means for determining a reference out of rated capability of the generator includes means for determining the magnitude of the generator output current as a function of the generator speed and the generator field current and means for setting the reference to the determined magnitude of generator output current.

26. The apparatus as claimed in claim 21, further comprising means for receiving a command indicative of a duty ratio of a power transistor of an IC regulator of a field current circuit provided for regulating generator field current of the generator.

27. The apparatus as claimed in claim 24, wherein the means for determining a reference out of rated capability of the generator includes means for determining the magnitude of the generator field current as a function of the generator output voltage and the duty ratio of the power transistor and means for setting the reference to the determined magnitude of the generator field current.