Double differential, electrically compensated constant speed drive

• US 4,734,626 A
• Filed: 12/23/1986
• Issued: 03/29/1988
• Est. Priority Date: 12/23/1986
• Status: Expired due to Fees

• Current Assignee: Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Sutrina, Thomas, Dishner, Bryan W.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): IP, SHIK LUEN PAUL
• Application Number:
  US06/945,869
• Time in Patent Office: 462 Days
• Field of Search: 318/76, 318/146, 318/147, 318/153, 318/157, 318/38, 318/12, 290/4 R, 290/4 C, 290/40 R, 322/14, 322/16, 322/25, 322/28, 322/29, 322/40, 363/41, 363/97, 363/98, 363/124, 323/267, 323/266, 307/87, 307/84
• US Class Current: 318/76
• CPC Class Codes: B60L 15/2054 by controlling transmissions or clutches
• CPC Class Codes: H02P 2101/30 for aircraft
• CPC Class Codes: H02P 9/06 Control effected upon clutch or other mechanical power transmission means and dependent upon electric output value of the generator
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

An electrically compensated constant speed drive (ECCSD) according to the present invention includes a pair of power transmission paths between the prime mover and a load wherein each power transmission path includes a mechanical differential having a first input coupled to the output of the prime mover and an output coupled to the load. A second input of each of the differentials is coupled to a permanent magnet machine and a power converter interconnects the electrical power windings of the permanent magnet machines. In operation, one of the permanent magnet machines is always operated as a generator while the other permanent magnet is operated as a motor so that power flow through the power converter is unidirectional. The ECCSD of the present invention results in a substantial reduction in the maximum control power and hence efficiency is increased and complexity is reduced.

Claims

1. A constant speed drive for developing constant speed motive power from variable speed motive power developed by a prime mover, comprising:

first and second differentials each having first and second inputs and an output, the differential outputs being coupled together and producing the constant speed motive power, the first input of the first and second differentials being coupled through gear sets to the output of the prime mover whereby the first input of the first differential is driven at a speed greater than a desired output speed of the drive and the first input of the second differential is driven at a speed less than the desired output speed;

a first permanent magnet machine coupled to the second input of the first differential, the first permanent magnet machine being driven as a generator to develop alternating current power at power windings thereof;

a second permanent magnet machine having a motive power shaft coupled to the second input of the second differential, the second permanent magnet machine including electrical power windings; and

a power converter interconnecting the power windings of the first and second permanent magnet machines for operating the second permanent magnet machine as a motor to develop compensating speed of appropriate magnitude and direction to cause the output of the second differential to develop motive power at the desired speed.

2. The constant speed drive of claim 1, wherein the power converter includes a rectifier coupled to the power windings of the first permanent magnet machine, a DC/DC converter coupled to the rectifier and an inverter coupled between the DC/DC converter and the power windings of the second permanent magnet machine.

3. The constant speed drive of claim 2, wherein the DC/DC converter comprises a buck/boost converter.

4. The constant speed drive of claim 2, wherein the DC/DC converter comprises a boost converter.

5. The constant speed drive of claim 4, wherein the power converter further includes means for controlling the inverter in a pulse-width modulated mode of operation when the voltage developed at the output of the rectifier is greater than that required to operate the second permanent magnet machine at the appropriate speed magnitude.

6. The constant speed drive of claim 2, wherein the DC/DC converter includes a power switch operated by a converter control.

7. The constant speed drive of claim 6, wherein the converter control comprises a pulse-width modulator.

8. A constant speed drive for developing constant speed motive power from variable speed motive power developed by a prime mover, comprising:

first and second differentials each having first and second inputs and an output, the differential outputs being coupled together and producing the constant speed motive power, the first input of the first and second differentials being coupled through gear sets to the output of the prime mover whereby the first input of the first differential is driven at a speed greater than a desired output speed of the drive and the first input of the second differential is driven at a speed less than the desired output speed;

a first permanent magnet machine having a motive power shaft coupled to the second input of the first differential, the first permanent magnet machine being driven as a generator to develop alternating current power at power windings thereof;

a second permanent magnet machine having a motive power shaft coupled to the second input of the second differential, the second permanent magnet machine including electrical power windings;

a rectifier circuit connected to the power windings of the first permanent magnet machine for rectifying the power developed by such machine to derive intermediate DC power;

a DC/DC converter coupled to the rectifier circuit;

an inverter coupled between the DC/DC converter and the power windings of the second permanent magnet machine; and

means for controlling the DC/DC converter and the inverter so that the second permanent magnet machine develops compensating speed of appropriate magnitude to cause the output of the second differential to develop motive power at the desired speed.

9. The constant speed drive of claim 8, wherein the DC/DC converter comprises a buck/boost converter.

10. The constant speed drive of claim 8, wherein the DC/DC converter comprises a boost converter.

11. The constant speed drive of claim 10, wherein the second permanent magnet machine develops a back emf and wherein the controlling means includes a pulse-width modulator for operating the inverter in a pulse-width modulated mode of operation when the voltage developed at the output of the rectifier is greater than the back emf developed by the second permanent magnet machine.

12. The constant speed drive of claim 8, wherein the DC/DC converter includes a power switch operated by the controlling means.

13. The constant speed drive of claim 12, wherein the controlling means includes a pulse-width modulator coupled to the power switch of the DC/DC converter.