WO1998044615A1 - Electronically commutated pole-changing motor - Google Patents

Electronically commutated pole-changing motor Download PDF

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Publication number
WO1998044615A1
WO1998044615A1 PCT/US1998/006136 US9806136W WO9844615A1 WO 1998044615 A1 WO1998044615 A1 WO 1998044615A1 US 9806136 W US9806136 W US 9806136W WO 9844615 A1 WO9844615 A1 WO 9844615A1
Authority
WO
WIPO (PCT)
Prior art keywords
rotor
motor
poles
stator
control circuit
Prior art date
Application number
PCT/US1998/006136
Other languages
French (fr)
Other versions
WO1998044615B1 (en
Inventor
Steven Belyo
Original Assignee
Dax Industries, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Dax Industries, Inc. filed Critical Dax Industries, Inc.
Priority to AU67831/98A priority Critical patent/AU6783198A/en
Publication of WO1998044615A1 publication Critical patent/WO1998044615A1/en
Publication of WO1998044615B1 publication Critical patent/WO1998044615B1/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P1/00—Arrangements for starting electric motors or dynamo-electric converters
    • H02P1/16—Arrangements for starting electric motors or dynamo-electric converters for starting dynamo-electric motors or dynamo-electric converters
    • H02P1/46—Arrangements for starting electric motors or dynamo-electric converters for starting dynamo-electric motors or dynamo-electric converters for starting an individual synchronous motor
    • H02P1/48—Arrangements for starting electric motors or dynamo-electric converters for starting dynamo-electric motors or dynamo-electric converters for starting an individual synchronous motor by pole-changing
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K19/00—Synchronous motors or generators
    • H02K19/02—Synchronous motors
    • H02K19/10—Synchronous motors for multi-phase current
    • H02K19/12—Synchronous motors for multi-phase current characterised by the arrangement of exciting windings, e.g. for self-excitation, compounding or pole-changing
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection

Definitions

  • the field of the invention is electric motors.
  • Electric motors generally include both a rotor and a stator. Both the rotor and stator each have one or more means for producing magnetic poles, examples of which are permanent magnets, electrical conductors (possibly forming coils), or combinations thereof.
  • the number of poles on the rotor and stator may be fixed, or may be variable. In many applications, it is desirable that the number of poles be variable so as to allow higher torque at lower speeds, and lower torque at higher speeds. Changing the number of poles in a motor is sometimes referred to as "pole-changing", and motors in which the number of poles can be varied are sometimes referred to as "pole-changing motors".
  • DC motors frequently utilize a commutator to reverse the polarity of the magnetic pole(s) of the rotor.
  • some DC motors might be called “brushless”, “commutatorless”, or “electronically commutated”, such motors generally differ from motors utilizing commutators in that there is no reversing of the polarity of the pole(s) of the rotor.
  • the rotor frequently comprises a permanent magnet and is forced to rotate by rotating the magnetic field of the stator. Examples can be seen in U.S. Patent No. 4,554,473 by Muller issued on November 19,1985, U.S. Patent No. 4,739,240 by MacMinn et al. issued on April 19, 1988, U.S. Patent No. 4,169,990 by Lerdman, issued on October 2, 1979, and U.S. Patent No. 4,668,898 by Harms et al. issued on May 26, 1987.
  • Methods and devices are provided for varying the number of poles on a rotor of an electrical motor by providing the rotor of the motor with a conductor control circuit which can control characteristics of the of the magnetic field generated by the rotor.
  • modifiable characteristics include polarity, field distribution, and field strength.
  • both the rotor and stator of a motor have conductor control circuits which are utilized to maintain an equal number of rotor and stator poles, while varying the number of poles such that a larger number of poles are used during low speeds than during high speeds.
  • the rotor control circuit utilizes "H" bridge transistor switching, with the transistors mounted on the rotor, and, through electronic switching, to act as an electronic commutator for the rotor.
  • Fig. 1 is a schematic view of a preferred embodiment of a conductor control circuit.
  • Fig. 2 is a schematic of an alternate embodiment of a conductor control circuit.
  • Fig. 3 is a schematic depicting a pole configuration preferred when low speed and high torque are desirable.
  • Fig. 4 is a schematic depicting a pole configuration preferred when mid-range speed and torque are desirable.
  • Fig. 5 is a schematic depicting a pole configuration preferred when high speed and low torque are desirable.
  • Fig. 6 is a diagram indicating how power varies with RPM when poles are decreased as acceleration increases.
  • both the rotor and stator of a motor could be provided with 36 separate coils.
  • Each coil could have a switching circuit such as that shown in Figure 1, associated with the coil. Because the switching circuit of figure 1 would allow the orientation of the pole associated with it to be reversed in polarity by reversing direction of current flow through the coil associated with it, pole configurations such as those shown in Figures 3, 4, and 5 could be obtained wherein the number of poles on the rotor and stator are kept equal, and the number of poles decreases as speed increases. It should be noted that, as shown in Figures 3, 4, and 5, although the actual number of separately actuated coils neither increases nor decreases, the grouping of like polarized coils effectively decreases the total number of magnetic poles.
  • any two adjacent magnetic poles have approximately equal magnitudes, but opposite polarities.
  • segregating poles of like polarity effectively increases the number of poles.
  • Less preferred alternative embodiments might involve utilizing different windings for different pole configurations wherein one or more windings might remain unused in certain configurations, and other windings might remain unused in other configurations.
  • any other pole-changing method could be utilized as well without departing from the inventive concepts disclosed herein.
  • the claimed invention need not be limited to stators or rotors size and shaped as those in figures 3, 4 and 5.
  • the number of coils on either or both could be varied where there would be at least 2, at least 6, or at least 36 coils. Or the number of coils might equal 2, 6 or 36 or be less than 2, 6, or 36.
  • the number of coils on the stator may differ from the number of coils on the rotor.
  • An alternative to focusing on number of coils would be to focus on the number of magnetic poles that could be generated.
  • the number of poles could be varied such that there were at least two, two, or more than two poles.
  • Figure 2 illustrates an alternative switching circuit to that shown in figure 1.
  • any other circuit mounted on the rotor which modifies the magnetic field generated by the rotor could be utilized as well. Modification of the magnetic field might simply consist of modifying the polarity of individual coils so as to group or ungroup coils. Other methods might be to vary other characteristics of the signals being communicated to the coil such as amplitude, frequency, and/or phase.

Abstract

Methods and devices are provided for varying the number of poles on a rotor of an electrical motor by providing the rotor of the motor with a conductor control circuit which can control characteristics of the magnetic field generated by the rotor. Examples of modifiable characteristics include polarity, field distribution, and field strength.

Description

ELECTRONICALLY COMMUTATED POLE-CHANGING MOTOR
Field of The Invention
The field of the invention is electric motors.
Background of The Invention
Electric motors generally include both a rotor and a stator. Both the rotor and stator each have one or more means for producing magnetic poles, examples of which are permanent magnets, electrical conductors (possibly forming coils), or combinations thereof. The number of poles on the rotor and stator may be fixed, or may be variable. In many applications, it is desirable that the number of poles be variable so as to allow higher torque at lower speeds, and lower torque at higher speeds. Changing the number of poles in a motor is sometimes referred to as "pole-changing", and motors in which the number of poles can be varied are sometimes referred to as "pole-changing motors". In a pole- changing motor, it is possible to vary the number of poles on the rotor, the stator, or both the rotor and stator. Examples in which the number of poles in the stator, but not the rotor, can be varied are found in several patents by Broadway et al., such as U.S. patents numbered 3,794,970, 3,898,543, 3,927,358, and 3,973,154, and in U.S. Patent No. 4,363,984 by Matsuda et al. issued on December 14, 1982. Patents focusing on winding methods to support pole changing include several patents by Auinger such as U.S. patents numbered 4,127,787, 4,144,470 and 4,529,472.
Providing a mechanism for varying the number of poles in the rotor tends to be problematic because of the fact that the rotor generally rotates, making it difficult to communicate an electrical signal to the rotor. One method for varying the number of poles in the rotor is to vary the number of electrical signals communicated to the rotor. However, utilizing this method tends to increase the size, complexity, and potential points of failure of the motor. As an example, for a motor which utilizes slip-rings to communicate electrical signals to the rotor, increasing the number of signals to be provided requires increasing the number of slip rings used. Similarly, in a motor utilizing brushes and commutators, increasing the number of signals may require increasing the number of brushes or the number or complexity of the commutators. Examples of this method are illustrated in U.S. Patent No. 5,311,615 by Coueteox issued on May 10, 1994 and U.S. Patent No. 5,134,351 by Msihid issued on July 28, 1992.
DC motors frequently utilize a commutator to reverse the polarity of the magnetic pole(s) of the rotor. Although some DC motors might be called "brushless", "commutatorless", or "electronically commutated", such motors generally differ from motors utilizing commutators in that there is no reversing of the polarity of the pole(s) of the rotor. Instead, the rotor frequently comprises a permanent magnet and is forced to rotate by rotating the magnetic field of the stator. Examples can be seen in U.S. Patent No. 4,554,473 by Muller issued on November 19,1985, U.S. Patent No. 4,739,240 by MacMinn et al. issued on April 19, 1988, U.S. Patent No. 4,169,990 by Lerdman, issued on October 2, 1979, and U.S. Patent No. 4,668,898 by Harms et al. issued on May 26, 1987.
Thus, there is a continuing need to improve electrical motors by providing new methods and devices for varying the number of poles of the rotor and to minimize the number of signals that must be communicated to the rotor.
Summary of the Invention
Methods and devices are provided for varying the number of poles on a rotor of an electrical motor by providing the rotor of the motor with a conductor control circuit which can control characteristics of the of the magnetic field generated by the rotor. Examples of modifiable characteristics include polarity, field distribution, and field strength.
In a preferred embodiment, both the rotor and stator of a motor have conductor control circuits which are utilized to maintain an equal number of rotor and stator poles, while varying the number of poles such that a larger number of poles are used during low speeds than during high speeds. Preferably, the rotor control circuit utilizes "H" bridge transistor switching, with the transistors mounted on the rotor, and, through electronic switching, to act as an electronic commutator for the rotor.
Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components. Brief Description of the Drawings
Fig. 1 is a schematic view of a preferred embodiment of a conductor control circuit.
Fig. 2 is a schematic of an alternate embodiment of a conductor control circuit.
Fig. 3 is a schematic depicting a pole configuration preferred when low speed and high torque are desirable.
Fig. 4 is a schematic depicting a pole configuration preferred when mid-range speed and torque are desirable.
Fig. 5 is a schematic depicting a pole configuration preferred when high speed and low torque are desirable.
Fig. 6 is a diagram indicating how power varies with RPM when poles are decreased as acceleration increases.
Detailed Description
Many of the past problems which arose in designing pole changing motors in which the number of poles on the rotor can eliminated simply by providing a control circuit on the rotor itself. Such a circuit could be fed one or more AC and/or DC signals through known methods such as slip rings or brushes, and could utilize those signals to generate and control the magnetic fields of the rotor. Controlling the magnetic field could include modifying the field's polarity, distribution, and field strength.
In a preferred embodiment, both the rotor and stator of a motor could be provided with 36 separate coils. Each coil could have a switching circuit such as that shown in Figure 1, associated with the coil. Because the switching circuit of figure 1 would allow the orientation of the pole associated with it to be reversed in polarity by reversing direction of current flow through the coil associated with it, pole configurations such as those shown in Figures 3, 4, and 5 could be obtained wherein the number of poles on the rotor and stator are kept equal, and the number of poles decreases as speed increases. It should be noted that, as shown in Figures 3, 4, and 5, although the actual number of separately actuated coils neither increases nor decreases, the grouping of like polarized coils effectively decreases the total number of magnetic poles. Thus, it is possible to obtain a pole configuration wherein any two adjacent magnetic poles have approximately equal magnitudes, but opposite polarities. Similarly, segregating poles of like polarity effectively increases the number of poles. Less preferred alternative embodiments might involve utilizing different windings for different pole configurations wherein one or more windings might remain unused in certain configurations, and other windings might remain unused in other configurations.
Although it is preferred to utilize a single layer of independent coils to form independent poles and utilize the grouping of the poles to increase or decrease the effective number of poles, any other pole-changing method, currently known or not, could be utilized as well without departing from the inventive concepts disclosed herein. Similarly, the claimed invention need not be limited to stators or rotors size and shaped as those in figures 3, 4 and 5. As an example, the number of coils on either or both could be varied where there would be at least 2, at least 6, or at least 36 coils. Or the number of coils might equal 2, 6 or 36 or be less than 2, 6, or 36. Additionally, the number of coils on the stator may differ from the number of coils on the rotor. An alternative to focusing on number of coils would be to focus on the number of magnetic poles that could be generated. As with varying the number of coils, the number of poles could be varied such that there were at least two, two, or more than two poles.
Figure 2 illustrates an alternative switching circuit to that shown in figure 1. Moreover, any other circuit mounted on the rotor which modifies the magnetic field generated by the rotor could be utilized as well. Modification of the magnetic field might simply consist of modifying the polarity of individual coils so as to group or ungroup coils. Other methods might be to vary other characteristics of the signals being communicated to the coil such as amplitude, frequency, and/or phase.
Thus, specific embodiments and applications of an electronically commutated pole- changing motor have been disclosed. It should be apparent, however, to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. For example, known variations in winding methods could be utilized to support the ability to vary the number poles. Similarly, it is possible to utilize "smarter" circuits to improve on the control methods herein disclosed. Also, the concepts herein are equally applicable to DC an AC motors and to both single and multi-phase motors. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims.

Claims

CLAIMSWhat is claimed is:
1. An electric motor comprising a rotor having
at least one electrical rotor conductor and
a rotor control circuit
wherein the rotor control circuit communicates at least one signal to the at least one rotor conductor to establish and control at least two magnetic poles.
2. The motor of claim 1 wherein any two adjacent magnetic poles have approximately equal magnitudes, but opposite polarities.
3. The motor of claim 1 wherein the total number of magnetic poles established can be
varied among at least N values wherein N is at least 2.
4. The motor of claim 3 wherein N is at least 6.
5. The motor of claim 3 wherein N is at least 36.
6. The motor of claim 1 wherein the rotor control circuit communicates the at least one
signal to the at least one rotor conductor in response to a rotor input signal.
7. The motor of claim 6 wherein the rotor further comprises a parameter detection circuit which communicates the rotor input signal to the rotor control circuit.
8. The motor of claim 1 further comprising a stator having at least one electrical stator
conductor and a stator control circuit wherein the stator control circuit communicates
at least one signal to the at least one stator conductor to establish at least two magnetic
poles.
9. The motor of claim 8 wherein the total number of stator poles is equal to the total number of rotor poles.
PCT/US1998/006136 1997-03-28 1998-03-27 Electronically commutated pole-changing motor WO1998044615A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU67831/98A AU6783198A (en) 1997-03-28 1998-03-27 Electronically commutated pole-changing motor

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US4213097P 1997-03-28 1997-03-28
US60/042,130 1997-03-28

Publications (2)

Publication Number Publication Date
WO1998044615A1 true WO1998044615A1 (en) 1998-10-08
WO1998044615B1 WO1998044615B1 (en) 1998-11-26

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Application Number Title Priority Date Filing Date
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AU (1) AU6783198A (en)
WO (1) WO1998044615A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102011077456A1 (en) * 2011-06-14 2012-12-20 Siemens Aktiengesellschaft Synchronous machine with HTS rotor

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE18811E (en) * 1929-06-21 1933-05-02 Multispeed synchronous dynamo-electric machine
US4477760A (en) * 1983-03-24 1984-10-16 Westinghouse Electric Corp. Continuous pole amplitude modulated electric machines
US4866364A (en) * 1986-06-27 1989-09-12 Tecnomasio Italiano Brown Boveri S.P.A. Power circuit for switching the number of poles on the rotor of synchronous machines by using rotative diodes
US5736829A (en) * 1994-08-02 1998-04-07 Performance Controls, Inc. High-speed constant-horsepower motor

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE18811E (en) * 1929-06-21 1933-05-02 Multispeed synchronous dynamo-electric machine
US4477760A (en) * 1983-03-24 1984-10-16 Westinghouse Electric Corp. Continuous pole amplitude modulated electric machines
US4866364A (en) * 1986-06-27 1989-09-12 Tecnomasio Italiano Brown Boveri S.P.A. Power circuit for switching the number of poles on the rotor of synchronous machines by using rotative diodes
US5736829A (en) * 1994-08-02 1998-04-07 Performance Controls, Inc. High-speed constant-horsepower motor

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102011077456A1 (en) * 2011-06-14 2012-12-20 Siemens Aktiengesellschaft Synchronous machine with HTS rotor

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AU6783198A (en) 1998-10-22

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