Quadrature axis field brushless exciter

• US 4,093,869 A
• Filed: 04/13/1976
• Issued: 06/06/1978
• Est. Priority Date: 04/13/1976
• Status: Expired due to Term

• Current Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Original Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Inventors: Gorden, Dale I., Kilgore, Lee A., Hoffmann, Arthur H.
• Primary Examiner(s): Schaefer, Robert K.
• Assistant Examiner(s): Mutter, Michael K.
• Application Number:
  US05/676,449
• Time in Patent Office: 784 Days
• Field of Search: 290/10, 290/22, 290/31, 290/32, 290/39, 290/46, 290/49.4, 290/52
• US Class Current: 290/31
• CPC Class Codes: H02K 19/12 characterised by the arrangement of exciting windings, e.g. for self-excitation, compounding or pole-changing
• CPC Class Codes: H02K 19/26 characterised by the arrangement of exciting windings

Abstract

Method and apparatus for accelerating a large inertia load from rest to a predetermined speed of rotation by means of a synchronous dynamoelectric machine. A synchronous dynamoelectric machine, such as a turbine generator, which is mechanically coupled to a gas turbine prime mover, is started synchronously to bring the gas turbine up to a speed which exceeds its stall speed under load. The rotor field winding of the synchronous dynamoelectric machine is connected to receive direct current excitation from a rotatable rectifier assembly of a brushless exciter. During starting, a quadrature axis winding disposed around the stator of the brushless exciter is energized by single phase alternating current. Alternating current excitation is induced by transformer action within the rotor armature winding of the exciter and is applied to the rotor field winding after being rectified by the rotatable rectifier assembly. The transformer action operates independently of the rotation of the rotor member of the synchronous dynamoelectric machine so that the brushless exciter develops direct current field excitation for starting purposes when the rotor is at rest. Polyphase alternating current excitation is applied to the synchronous dynamoelectric machine stator winding to establish a dynamic magnetic field which rotates at a speed proportional to the frequency of the applied excitation. Interaction of the static magnetic field of the rotor and the rotating stator field produces the mechanical turning force. The frequency of the synchronously applied stator excitation is increased from substantially zero cycles per second to a higher frequency until the rotor member has accelerated synchronously to the desired speed of rotation.

Claims

1. In combination,

a synchronous dynamoelectric machine having a stator member carrying a polyphase alternating current stator winding and a rotor member carrying a direct current rotor field winding;

and,

a main exciter for said synchronous dynamoelectric machine having a rotatable armature winding and rectifier connected to conduct direct current to said rotor field winding, a stator core comprising a plurality of salient poles, a plurality of field coils disposed on selected ones of said salient poles, said field coils being connected together to constitute a direct current stator field winding, and at least one starting coil interposed between salient poles, the magnetic axis of said starting coil being disposed substantially in space-quadrature relation with respect to the magnetic axes of adjacent field coils, said starting coil being disposed to induce alternating current in said armature winding when said starting coil is energized by a single phase alternating current source.

2. The combination as defined in claim 1 including:

means for providing variable frequency polyphase alternating current excitation to said polyphase alternating current armature winding during startup of said dynamoelectric machine.

3. The combination as defined in claim 2 wherein said means for providing variable frequency polyphase alternating current excitation is a cycloconverter having a polyphase input circuit connected to receive polyphase alternating current from a supplemental polyphase power source and a polyphase output circuit connected to conduct polyphase alternating current excitation to said stator winding, said cycloconverter being operable to convert said input polyphase alternating current of a first amplitude and a first frequency to output polyphase alternating current excitation having an output frequency which is variable through a predetermined frequency range and an output magnitude which is variable through a predetermined magnitude range.

4. The combination as defined in claim 1 including a large inertia load, said load having a rotatable shaft portion mechanically coupled in driving relation to said rotor member for rotation therewith.

5. The combination defined by claim 4 in which said large inertia load is a gas turbine prime mover.

6. A dynamoelectric machine comprising, in combination:

a shaft;

a rotatable armature member disposed on said shaft, said armature member carrying an armature winding;

a stator member having a plurality of salient poles thereon concentrically disposed about and spaced apart from said armature;

a stator field coil disposed on selected ones of said salient poles, said stator field coils being connected together to constitute a stator field winding; and

,

a plurality of alternating current induction coils interposed between adjacent ones of said salient poles, the magnetic axes of said induction coils being disposed substantially in space quadrature relation with respect to the magnetic axes of said field coils, said induction coils being connected together to constitute a single phase an alternating current starting winding.

7. In a synchronous dynamoelectric machine, a rotor member having field coils connected together to form a rotor field winding, an alternating current exciter having a stator member and a plurality of salient stator poles thereon, stator field coils disposed on said salient poles and connected together to form a stator exciter field winding and at least one starting coil interposed between salient poles, the magnetic axis of said starting coil being disposed substantially in space-quadrature relation with respect to the magnetic axes of adjacent field coils, an exciter armature member rotatable with said rotor field winding and having an armature winding thereon, said exciter armature winding being coupled magnetically with said exciter stator field winding for developing an alternating current excitation signal within said armature winding, rectifier means interconnecting said armature winding and said rotor field winding to provide direct current excitation to said rotor field winding;

the combination with said synchronous dynamoelectric machine of means connected to a supplemental source of single phase alternating current to induce by magnet induction an alternating current excitation signal within said exciter armature winding when said rotor is at standstill, whereby direct current excitation is provided to said rotor field winding by said rectifier means independently of rotor rotation to permit acceleration of said rotor from rest to a predetermined operating speed by the interaction of the static magnetic field established by the rotor field winding with the rotating magnetic field established by the dynamoelectric machine stator winding in response to polyphase alternating current excitation applied thereto, the frequency of said polyphase excitation being variable in frequency from substantially zero cycles per second to a higher frequency which corresponds with the rotation of said rotor at a speed substantially equal to said predetermined operating speed.

8. A method of accelerating the rotor member of a synchronous dynamoelectric machine from rest to a predetermined speed of rotation, said dynamoelectric machine having a brushless exciter with a quadrature axis winding around the stator of said exciter, said dynamoelectric machine having a polyphase alternating current stator winding and a direct current rotor field winding, said method comprising:

exciting the rotor field winding of said rotor member with direct current to establish a static magnetic field by connecting said rotor field winding to receive direct current excitation from the rotatable rectifier assembly of a brushless exciter, said brushless exciter including an alternator having a direct-axis, direct current stator winding and an alternating current quadrature-axis winding, the step of exciting the field winding of said synchronous dynamoelectric machine being accomplished by;

exciting said quadrature axis winding of the stator of said exciter with single phase alternating current, whereby alternating current is induced within the rotor armature winding of said exciter and direct current excitation is applied to said rotor field winding through said rotatable rectifier independently of the rotation of said rotor member;

exciting the stator winding of said dynamolelectric machine with polyphase alternating current to establish a dynamic magnetic field which rotates at a speed proportional to the frequency of the applied polyphase alternating current excitation; and

,

increasing the frequency of the applied polyphase alternating current excitation from substantially zero cycles per second to a higher frequency until said rotor member has accelerated to said predetermined speed of rotation.

9. The method as defined in claim 8 wherein said rotor member is mechanically coupled in driving relation to the rotor member of a prime mover, the step of increasing the frequency of the applied polyphase alternating current excitation being continued until the rotor member of said prime mover and said rotor of said synchronous dynamoelectric machine have accelerated to a speed at which the starting resistance torque of said dynamolelectric machine is less than the power output torque of said prime mover.

10. The method as defined in claim 8 including the step of increasing the magnitude of the applied polyphase alternating current excitation in proportion to the frequency of said applied excitation.