Electric load damper for damping torsional oscillation

• US 8,217,630 B2
• Filed: 11/18/2009
• Issued: 07/10/2012
• Est. Priority Date: 11/18/2009
• Status: Active Grant

• Current Assignee: Hamilton Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Hamilton Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Markunas, Albert L., Madalli, Vijay K., Baker, Donal E., Sagona, John
• Primary Examiner(s): Cuevas, Pedro J
• Application Number:
  US12/620,625
• Publication Number:
  US 20110115444A1
• Time in Patent Office: 965 Days
• Field of Search: 322/36, 290/14
• US Class Current: 322/36
• CPC Class Codes: H02P 2101/30 for aircraft
• CPC Class Codes: H02P 9/102 for limiting effects of transients
• CPC Class Codes: H02P 9/16 due to variation of ohmic resistance in field circuit, using resistances switched in or out of circuit step by step
• CPC Class Codes: H02P 9/302 Brushless excitation

Abstract

An electric load damper assembly includes a synchronous generator operable to provide a plurality of phases of electrical output in response to a mechanical input from a rotating shaft. An electric load damper includes a phase leg for each of the plurality of phases. Each phase leg includes a resistive load, a snubber and at least one solid state switch. The at least one solid state switch is in parallel with the snubber, and the at least one solid state switch and snubber are collectively in series with the resistive load. A controller is operable to receive a signal indicative of a rotational speed oscillation of the synchronous generator, and is operable to selectively reduce a torsional oscillation of the shaft by diverting electrical current from the synchronous generator through the resistive load of each of the plurality of phases in response to the signal exceeding a predefined threshold.

Claims

1. An electric load damper assembly, comprising:

a synchronous generator operable to provide a plurality of phases of electrical output in response to a mechanical input from a rotating shaft;

an electric load damper including a phase leg for each of the plurality of phases, each phase leg comprising;

a resistive load;

a snubber; and

at least one solid state switch connected in parallel with the snubber, the at least one solid state switch and snubber being collectively connected in series with the resistive load; and

a controller operable to receive a signal indicative of a rotational speed oscillation of the synchronous generator, and operable to selectively reduce a torsional oscillation of the shaft by diverting electrical current from the synchronous generator through the resistive load of each of the plurality of phases in response to the signal exceeding a predefined rotational speed oscillation threshold.

2. The assembly of claim 1, wherein the resistive loads for each of the plurality of phases are connected to a common node, and an input of each phase leg of the electric load damper is connected to one of the plurality of phases, such that the phase legs are Y-connected.

3. The assembly of claim 1, wherein each of the plurality of phases of current is connected to an input of a first phase leg of the electric load damper and an output of a second phase leg of the electric load damper, such that the phase legs are delta-connected.

4. The assembly of claim 1, wherein the at least one solid state switch includes a first MOSFET and a second MOSFET, the first MOSFET and the second MOSFET being oriented to prevent a flow of current when in an OFF state.

5. The assembly of claim 4, wherein a drain of the first MOSFET is connected in series to a drain of the second MOSFET.

6. The assembly of claim 1, wherein the controller diverts electrical current from the synchronous generator through each resistive load by turning ON the at least one solid state switch for each of the phase legs.

7. The assembly of claim 1, wherein the controller only turns the at least one solid state switch ON during positive half cycles of the signal.

8. The assembly of claim 4, wherein the controller stops turning the at least one solid state switch ON during positive half cycles of the signal when the oscillations no longer exceed the predefined rotational speed oscillation threshold.

9. The assembly of claim 1, further comprising a heat sink operable to dissipate heat generated by each resistive load.

10. The assembly of claim 1, further comprising a generator control unit operable to provide excitation energy to the synchronous generator, and operable to provide the signal indicative of a rotational speed oscillation of the synchronous generator to the controller.

11. A method of damping torsional oscillation, comprising:

receiving a signal indicative of a rotational speed oscillation of a synchronous generator, the synchronous generator being driven by a rotating shaft; and

diverting electrical current from each of a plurality of phases of the synchronous generator through a plurality of resistive loads, each resistive load corresponding to one of the plurality of phases to reduce a torsional oscillation of the shaft in response to the oscillations exceeding a predefined rotational speed oscillation threshold.

12. The method of claim 11, wherein said step of diverting electrical current is selectively repeated until the oscillations are within the predefined rotational speed oscillation threshold.

13. The method of claim 11, wherein said step of diverting electrical current is only performed during positive half cycles of the signal.

14. The method of claim 11, wherein said step of diverting electrical current is only performed in response to a determination that the resistive load has the capacity to absorb additional energy.

15. The method of claim 11, further comprising:

dissipating heat from the resistive load through a heat sink.

16. An aircraft torsional oscillation damping system, comprising:

a gas turbine engine having at least one rotating shaft;

at least one synchronous generator operable to provide a plurality of phases of electrical output in response to a mechanical input from a rotating shaft;

at least one electric load damper, each of the at least one synchronous generators having an associated electric load damper, the at least one electric load damper including a phase leg for each of the plurality of phases, each phase leg comprising;

a resistive load;

a snubber; and

at least one solid state switch in parallel with the snubber, the at least one solid state switch and snubber being collectively in series with the resistive load; and

a controller operable to receive a signal indicative of a rotational speed oscillation of the synchronous generator, and operable to selectively reduce a torsional oscillation of the shaft by diverting electrical current from the synchronous generator through the resistive load of each of the plurality of phases in response to the signal exceeding a predefined rotational speed oscillation threshold.

17. The assembly of claim 16, wherein the controller only diverts electrical current from the synchronous generator through the resistive load during positive half cycles of the signal.

18. The assembly of claim 16, further comprising a generator control unit operable to provide excitation energy to the synchronous generator, and operable to provide the signal indicative of a rotational speed of the synchronous generator to the controller.

19. The assembly of claim 16, wherein the electric load damper and the controller are configured to supplement or replace a mechanical load damper in an aircraft.