Starting system and method using a hybrid permanent magnet/induction machine

• US 4,830,412 A
• Filed: 11/30/1987
• Issued: 05/16/1989
• Est. Priority Date: 10/26/1987
• 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: Raad, Bernard A., Dolan, Clarence F.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Logan, Sharon D.
• Application Number:
  US07/112,701
• Time in Patent Office: 533 Days
• Field of Search: 290/31, 290/38 R, 290/46, 290/4 R, 290/4 C, 310/211, 322/10, 322/29
• US Class Current: 290/31
• CPC Class Codes: F02N 11/04 the motors being associated with current generators
• CPC Class Codes: H02K 21/46 Motors having additional short-circuited winding for starting as an asynchronous motor

Abstract

A starting system and method for starting a prime mover connected to a generator by an actuable torque link utilizes a hybrid permanent magnet/induction machine having a rotor coupled to a rotor of the main generator and a stator having windings therein. The method includes the step of applying AC power to the hybrid machine stator windings so that the hybrid machine initially acts as an induction motor to accelerate the hybrid machine rotor, following which the hybrid machine acts as a synchronous motor to rotate the main generator rotor at a particular speed DC power is then applied to a main generator field winding and AC power is supplied to a set of main generator armature windings so that the main generator operates as a synchronous motor to develop motive power the torque link is activated once the main generator is operating as a synchronous motor to bring the prime mover up to self-sustaining speed. Inasmuch as the hybrid machine may comprise part of a brushless synchronous generator, the present system and method does not require additional components and reduces transients in the AC power applied to the hybrid machine and generator.

Claims

1. A starting system for starting a prime mover selectively coupled to a rotor of a generator by an actuable torque link, the generator including a field winding disposed on the rotor and at least one armature winding disposed in a stator, comprising:

a hybrid permanent magnet/induction machine having a rotor coupled to the generator rotor and stator windings disposed in a stator;

a source of AC power selectively connectable to the stator windings of the hybrid machine to accelerate the hybrid machine rotor in an induction mode to a synchronous speed at which time the machine operates in a synchronous mode as a motor to rotate the generator rotor at a particular speed; and

means for applying power to the generator field winding and to the generator armature windings once the generator rotor is rotating at the particular speed so that the generator operates as a synchronous motor whereupon the torque link is actuated to connect the generator to the prime mover to bring the prime mover up to self-sustaining speed.

2. The starting system of claim 1, wherein the hybrid machine includes at least two permanent magnets and a squirrel-cage winding disposed on the rotor thereof.

3. The starting system of claim 2, wherein the permanent magnet includes two poles separated by interpole regions and wherein the squirrel-cage winding is disposed in the interpole regions.

4. The starting system of claim 1, wherein the main generator is a synchronous machine having a synchronous speed equal to the synchronous of the hybrid machine.

5. A method of starting a prime mover using a main generator selectively coupled to the prime mover by an actuable torque link, a hybrid permanent magnet/induction machine having a rotor coupled to a rotor of the main generator and a stator having a winding therein, the main generator including field and armature windings, the method comprising the steps of

(a) applying AC power to the hybrid machine stator winding so that the hybrid machine initially acts as an induction motor to accelerate the hybrid machine rotor, following which the hybrid machine acts as a synchronous motor to rotate the main generator rotor at a particular speed;

(b) applying DC power to the main generator field winding and AC power to the main generator armature windings once the main generator rotor is rotating at the particular speed so that the main generator operates as a synchronous motor; and

(c) actuating the torque link once the main generator is operating as a synchronous motor to bring the prime mover up to self-sustaining speed.

6. The method of claim 5, wherein the step (a) includes the step of providing AC power at a constant frequency to the hybrid machine and the step (b) includes the step of applying AC power at the constant frequency to the main generator armature winding.

7. The method of claim 5, wherein the main generator is a synchronous machine leaving a synrhconous speed and wherein the particular speed of the main generator rotor is equal to its synchronous speed.