Method and apparatus for improving performance of AC machines

• US 5,189,357 A
• Filed: 07/17/1989
• Issued: 02/23/1993
• Est. Priority Date: 07/22/1986
• Status: Expired due to Fees

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Inventors: Hsu, John S., Woodson, Herbert H.
• Primary Examiner(s): Smith, Jr., David
• Application Number:
  US07/382,078
• Time in Patent Office: 1,317 Days
• Field of Search: 363/39, 363/43, 363/41, 318/730, 318/737, 318/831, 318/832, 318/773-775, 318/812, 318/807, 310/184
• US Class Current: 318/737
• CPC Class Codes: H02K 3/28 Layout of windings or of connections between windings windings for pole-changing H02K17/06, H02K17/14, H02K19/12, H02K19/32
• CPC Class Codes: H02M 5/452 with automatic control of output waveform
• CPC Class Codes: H02P 6/187 using the star point voltage

Abstract

A method and apparatus for improving the performance of polyphase AC machines. The polyphase AC machines are excited both with a fundamental frequency and with an odd harmonic of the fundamental frequency. The fundamental flux wave and the harmonic flux wave will travel at synchronous speed in the air gap. This facilitates redistributing the flux densities in the machine and thereby increasing the total flux per pole in the machine.

Claims

1. A method of exciting a polyphase alternating current machine having a set of windings formed therein wherein at least a first portion of said winding have a preselected number of poles associated therewith, and at least a second portion of said windings have an odd multiple preselected number of poles associated therewith, comprising the steps of:

exciting at least said first portion of the windings of said machine with a polyphase fundamental frequency current so that a fundamental flux wave rotates in an air gap of said machine at a speed corresponding to the frequency of said fundamental frequency current; and

exciting at least said second portion of the windings of said machine with an odd harmonic frequency of said fundamental frequency current so that a harmonic flux wave rotates in the air gap of said machine at a speed substantially synchronous with said fundamental flux wave.

2. The method of claim 1, wherein said machine is excited by a fundamental frequency current by applying said fundamental frequency current to a first set of windings, and wherein said machine is excited with an odd harmonic frequency current by applying said odd harmonic frequency current to a second set of windings.

3. The method of claim 1, wherein said fundamental frequency current and said harmonic frequency current are applied to single set of windings.

4. The method of claim 3, wherein the windings in said single set of windings are connected in a plurality of deltas.

5. The method of claim 4, wherein said deltas are current balanced relative to one another.

6. The method of claim 4, wherein said deltas are coupled to one another through transformers.

7. The method of claim 6, wherein one phase of said odd harmonic frequency current is applied to each leg of one of said deltas.

8. A method of operating an alternating current machine having a set of windings formed therein wherein at least a first portion of said windings have a preselected number of poles associated therewith, and at least a second portion of said windings have an odd multiple preselected number of poles associated therewith, comprising the steps of:

generating a fundamental flow wave in an air gap of said machine by exciting at least said first portion of said windings with a fundamental frequency current; and

generating an odd harmonic flux wave in said air gap of said machine by exciting at least said second portion of said windings with an odd harmonic frequency current of said fundamental frequency current, said harmonic flux wave moving in said air gap in synchronous relation to said fundamental flux wave.

9. A polyphase alternating current machine having at least one set of windings formed therein where at least a first portion of said windings have a preselected number of poles associated therewith, and at least a second portion of said windings have an odd multiple preselected number of poles associated therewith, comprising:

means for exciting at least said first portion of said windings with a polyphase fundamental frequency current to generate a fundamental flux wave rotating in an air gap of said machine; and

means for exciting at least said second portion of said windings with an odd harmonic frequency current of said fundamental frequency current to generate a harmonic flux wave rotating in the air gap of said machine in synchronous relation with said fundamental flux wave.

10. The method of claim 9, wherein said machine comprises a first set of windings adapted for being excited by said fundamental frequency current and a second set of windings adapted for being excited by said odd harmonic frequency current.

11. An alternating current machine having a set of windings formed therein wherein at least a first portion of said windings have a preselected number of poles associated therewith, and at least a second portion of said windings have an odd multiple preselected number of poles associated therewith, comprising:

means for generating a fundamental flux wave in an air gap of said machine by exciting said first portion of said windings with a fundamental frequency current; and

means for generating a harmonic flux wave in said air gap of said machine by exciting said second portion of said windings with an odd harmonic frequency current of said fundamental frequency current, said harmonic flux wave moving in said air gap in synchronous relation to said fundamental flux wave.

12. A method for exciting a polyphase alternating current machine to controllably produce a flux wave of a preselected configuration in an air gap of said machine, said machine having a set of windings formed therein wherein at least a first portion of said windings have a preselected number of poles associated therewith, and at least a second portion of said windings have an odd multiple preselected number of poles associated therewith, comprising the steps of:

exciting at least said first portion of said windings with a polyphase fundamental frequency current so that a fundamental flux wave rotates in the air gap of said machine at a speed corresponding to the frequency of said fundamental current;

exciting at least said second portion of said windings with an odd harmonic frequency of said fundamental frequency current, said odd harmonic frequency excitation being approximately in phase with said fundamental frequency current so that an odd harmonic flux wave rotates in the air gap of said machine at a speed substantially identical to the frequency of said fundamental flux wave; and

combining said fundamental and harmonic waves to produce a resultant flux wave having a peak amplitude less than the amplitude of the fundamental flux wave.

13. A method, as set forth in claim 12, wherein said step of exciting said machine with a polyphase fundamental frequency current includes applying said fundamental frequency current to a first set of windings, and wherein said step of exciting said machine with an odd harmonic frequency includes applying said odd harmonic frequency current to a second set of windings.

14. A method, as set forth in claim 12, wherein the steps of exciting said machine with the polyphase fundamental frequency current and the odd harmonic frequency current includes applying said fundamental frequency current and said odd harmonic frequency current to a single set of windings.

15. A method for exciting a polyphase alternating current machine to controllably produce a flux wave of a preselected configuration in an air gap of said machine, said machine having a set of windings formed therein wherein at least a first portion of said windings have a preselected number of poles associated therewith, and at least a second portion of said windings have an odd multiple preselected number of poles associated therewith, comprising the steps of:

generating a fundamental flux wave rotating in the air gap of said machine at a first preselected speed by exciting at least said first portion of said windings with a polyphase fundamental frequency current;

generating an odd harmonic flux wave rotating in the air gap of said machine at said first preselected speed substantially in phase with said fundamental flux wave by exciting at least said second portion of said windings with an odd harmonic frequency current of said fundamental frequency current; and

combining said fundamental and odd harmonic flux waves to produce a resultant flux wave having a peak amplitude less than the amplitude of the fundamental flux wave.

16. A method for exciting a polyphase alternating current machine to controllably produce a flux wave of a preselected configuration in an air gap of said machine having a set of windings formed therein wherein at least a first portion of said windings have a preselected number of poles associated therewith, and at least a second portion of said windings have an odd multiple preselected number of poles associated therewith, comprising the steps of:

generating a fundamental flux wave rotating in the air gap of said machine at a first preselected speed by exciting at least said first portion of said windings with a polyphase fundamental frequency current;

generating an odd harmonic flux wave rotating in the air gap of said machine at substantially the same speed as said first preselected speed by exciting at least said second portion of said windings with an odd harmonic frequency current of said fundamental frequency current; and

adjusting the phase relationship of said harmonic flux wave relative to said fundamental flux wave to produce a resultant flux wave having a peak amplitude less than the amplitude of the fundamental flux wave.

17. An apparatus for exciting a polyphase alternating current machine having at least one set of stator windings to controllably produce a flux wave of a preselected configuration in an air gap of said machine, at least a first portion of said windings having preselected number of poles associated therewith, and at least a second portion of said windings having an odd multiple preselected number of poles associated therewith, comprising:

means for exciting at least the first portion of said windings with a polyphase fundamental frequency current and generating a resultant fundamental flux wave rotating in the air gap of said machine at a first preselected speed;

means for exciting at least the second portion of said windings with an odd harmonic frequency current of said fundamental frequency current and generating a resultant odd harmonic flux wave rotating in the air gap of said machine at said first preselected speed; and

means for adjusting the phase relationship of said harmonic flux wave relative to said fundamental flux wave to produce a resultant flux wave having a peak amplitude less than the amplitude of the fundamental flux wave.

18. An apparatus for exciting a polyphase alternating current machine to controllably produce a flux wave of a preselected configuration in an air gap of said machine, having a set of windings formed therein wherein at least a first portion of said windings have a preselected number of poles associated therewith, and at least a second portion of said windings have no odd multiple preselected number of poles associated therewith, comprising:

means for exciting at least said first portion of said windings with a polyphase fundamental frequency current so that a fundamental flux wave rotates in the air gap of said machine at a speed corresponding to the frequency of said fundamental current;

means for exciting at least said second portion of said windings with an odd harmonic frequency of said fundamental frequency current, said odd harmonic frequency excitation being substantially in phase with said fundamental frequency current so that an odd harmonic flux wave rotates in the air gap of said machine at a speed corresponding to the frequency of said fundamental current, said fundamental and harmonic flux waves combining to produce an air gap resultant flux wave having a peak amplitude less than the amplitude of the fundamental flux wave.

19. An apparatus for exciting a polyphase alternating current machine having at least one set of stator windings to controllably produce a flux wave of a preselected configuration in selected portions of said machine, at least a first portion of said windings having preselected number of poles associated therewith, and at least a second portion of said windings having an odd multiple preselected number of poles associated therewith, comprising:

a sinusoidal fundamental frequency current source connected to at least said first portion of said stator windings and adapted for exciting the windings of said machine to produce a fundamental flux wave rotating about an air gap in said machine at a speed corresponding to the frequency of said fundamental frequency;

a sinusoidal odd harmonic frequency current source connected to at least said second portion of said stator windings and adapted for exciting the windings of said machine to produce an odd harmonic flux wave rotating about the air gap of said machine at a speed substantially synchronous with said fundamental flux wave; and

means for adjusting the phase relation of said odd harmonic current relative to said fundamental frequency current to produce a resultant flux wave having a substantially rectangular configuration.