Aircraft turbine start from a low voltage battery

• US 5,036,267 A
• Filed: 12/15/1989
• Issued: 07/30/1991
• Est. Priority Date: 12/15/1989
• Status: Expired due to Term

• Current Assignee: Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Markunas, Albert L., Rozman, Gregory I.
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): KINCAID, KRISTINE LYNN
• Application Number:
  US07/451,447
• Time in Patent Office: 592 Days
• Field of Search: 322/10, 322/11, 322/14, 322/29, 290/31, 290/38 R, 290/46, 363/57, 363/58, 363/96
• US Class Current: 322/10
• CPC Class Codes: F02N 11/04 the motors being associated with current generators
• CPC Class Codes: F05B 2220/50 for auxiliary power units (APU's)

Abstract

A low voltage battery provides the power source for energizing an aircraft generator to operate it as a motor during a starting operation. The battery is coupled to an input to an inverter whose a.c. output is controlled by a pulse width modulator. By controlling the switching points of the output, the generator is so energized that it operates as a brushless d.c. motor. At a point where the available voltage to the generator is insufficient to further accelerate the turbine, even with field weakening and an increased commutation angle, an autotransformer is switched into the system to step up the output voltage from the invertor. Throughout the starting operation the commutation angle is controlled so that current drain on battery is such that the battery terminal voltage at one half its no load terminal voltage, thus providing maximum power transfer from the battery.

Claims

1. A system for starting an aircraft turbine from a low voltage power supply by energizing a generator coupled to said turbine to operate as a motor during starting, comprising in combination:

an inverter having a direct current input coupled to said low voltage battery and an alternating current output;

an autotransformer having a starting mode input tap and a starting mode output tap, said autotransformer coupling a stepped up voltage between said input tap and output tap;

means for coupling said output tap to said generator;

control means for coupling said inverter output to said generator initially during starting and thereafter coupling said inverter output to said transformer input tap; and

means for controlling the input current to said generator to maintain the battery terminal voltage during starting at a predetermined level.

2. A system for starting an aircraft turbine as in claim 1, wherein said predetermined level is approximately equal to one half the no load battery terminal voltage.

7. A system for starting an aircraft turbine as in claim 1 wherein said generator operates as a brushless d.c. motor.

3. A system for starting an aircraft turbine by energizing a generator coupled to said turbine from a low voltage battery power supply to cause said generator to operate as a motor, comprising in combination:

an inverter having a direct current input coupled to said low voltage battery and an alternating current output;

control means for coupling said inverter output to said generator during starting; and

means for controlling the input current to said generator during starting to maintain the battery terminal voltage at a level approximately equal to one half the no load battery terminal voltage.

4. A system for starting an aircraft turbine as in claim 3 wherein said means for controlling input current includes means for controlling the commutation angle of said generator.

5. A system for starting an aircraft turbine as in claim 3 wherein said coupling means includes an autotransformer.

6. A system for starting an aircraft turbine as in claim 4 wherein said coupling means includes an autotransformer.