LOAD-OFF TRANSIENT ACCELERATION GENERATOR CONTROL SYSTEM

• US 20090072797A1
• Filed: 07/11/2007
• Published: 03/19/2009
• Est. Priority Date: 07/11/2007
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Malicki, Wally A., Fuller, Randy J., Yao, Yuan
• Granted Patent: US 7,633,272 B2
• Time in Patent Office: Days
• US Class Current: 322/19
• CPC Class Codes: H02P 2101/30 for aircraft
• CPC Class Codes: H02P 2101/45 for motor vehicles, e.g. car alternators
• CPC Class Codes: H02P 29/0241 the fault being an overvoltage
• CPC Class Codes: H02P 9/10 Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load

Abstract

An electric generator is operated under conditions in which rapid off-loading may occur. A generator control unit (GCU) employs a detector to detect rates of change of output of the generator. In response to a rapid change of output, e.g. an off-loading, an overvoltage protection system is activated. Excess energy stored is an excited winding is directed into an impedance circuit thus precluding overvoltage that may have been produced by the excess energy.

Claims

1. An electrical generator assembly with a field discharging system comprising:

a detection unit adapted to trigger operation of the field-discharging system, the detector comprises;

a detector responsive to a rate of change of generator output.

2. The generator assembly of claim 1 wherein the detector responds to a rate of change of current.

3. The generator assembly of claim 1 wherein the detector responds to a rate of change of voltage.

4. The generator assembly of claim 1 wherein:

the detection unit comprises;

a detector responsive to a rate of change of POR voltage; and

a detector responsive a rate of change of field current.

5. The generator assembly of claim 1 wherein:

the detection unit is responsive to both POR voltage and the rate of change of generator output; and

the detection unit is adapted to activate the field-discharging system only when the detected POR voltage is at least as high as about 90% to about 100% of a desired POR voltage of the generator.

6. The generator assembly of claim 1 wherein:

the detection unit is responsive to both POR voltage and rate of change of POR voltage; and

the detection unit is adapted to activate the field-discharging system only when the detected POR voltage is at least as high as about 90% to about 100% of a desired POR voltage of the generator.

7. A load-off protection system for an electrical generator comprising:

a first detector responsive to POR voltage of the generator;

a second detector responsive to a rate of change of generator output; and

a field current discharging system responsive to an activation signal that is produced when the first detector detects a baseline voltage and the second detector produces a do/dt signal when a threshold rate of change of output is detected.

8. The load-off protection system of claim 7 wherein:

the second detector is responsive to a rate of change of POR voltage and produces a dv/dt signal when a threshold dv/dt is detected; and

the activation signal is produced when the dv/dt signal is produced and the baseline voltage is detected by the first detector.

9. The load-off protection system of claim 7 wherein:

the second detector is responsive to a rate of change of field current of the generator and produces a di/dt signal when a threshold di/dt is detected; and

the activation signal is produced when the di/dt signal is produced and the baseline voltage is detected by the first detector.

10. The load-off protection system of claim 9 further comprising a third detector responsive to a rate of change of POR voltage and produces a dv/dt signal when a threshold dv/dt is detected.

11. The load-off protection system of claim 10 wherein the activation signal is be produced when either the dv/dt threshold or the di/dt threshold is detected and the baseline voltage is detected.

12. A method for controlling an electrical generator comprising the steps of:

detecting a rate of change of output of the generator; and

discharging field current when the rate of change of output reaches a predetermined value.

13. The method of claim 12 wherein the step of detecting a rate of change of output comprises detecting a rate of change of POR voltage of the generator.

14. The method of claim 13 further comprising the steps of:

detecting POR voltage of the generator;

integrating the detected POR voltage with the detected rate of change of the output of the generator to produce an activation signal when the POR voltage reaches a baseline value and the rate of change of POR voltage reaches a predetermined value; and

wherein the field current of the generator is discharged when the activation signal is produced.

15. The method of claim 14 wherein the baseline value of the detected POR voltage is between about 90% and 100% of a desired POR voltage of the generator.

16. The method of claim 12 wherein the step of detecting a rate of change of output comprises detecting a rate of change of field current of the generator.

17. The method of claim 16 further comprising the steps of:

detecting POR voltage of the generator;

integrating the detected POR voltage with the detected rate of change of the field current of the generator to produce an activation signal when the POR voltage reaches a baseline value and the rate of change of field current reaches a predetermined value; and

wherein the field current of the generator is discharged when the activation signal is produced.

18. The method of claim 17 wherein the baseline value of the detected POR voltage is between about 90% and 100% of a desired POR voltage of the generator.

19. The method of claim 17 wherein the predetermined value of the detected rate of change of POR voltage is between about 5 volts/millisecond and about 20 volts/millisecond.

20. The method of claim 12 further comprising the steps of:

detecting POR voltage of the generator;

integrating the detected POR voltage with a detected rate of change of the POR voltage of the generator to produce a first activation signal if the POR voltage reaches a baseline value and the rate of change of POR voltage reaches a predetermined value;

integrating the detected POR voltage with a detected rate of change of the field current of the generator to produce a second activation signal if the POR voltage reaches a baseline value and the rate of change of field current reaches a predetermined value; and

discharging the field current upon production of either the first activation signal or the second activation signal.