Electrical drive systems

• US 4,782,272 A
• Filed: 07/17/1985
• Issued: 11/01/1988
• Est. Priority Date: 06/28/1985
• Status: Expired due to Term

• Current Assignee: Kollmorgen Corporation (Regal Rexnord Corp.)
• Original Assignee: Kollmorgen Technologies Corporation
• Inventors: Murray, Aengus, Buckley, Maurice, Stone, Arthur
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US06/755,786
• Time in Patent Office: 1,203 Days
• Field of Search: 318/138, 318/254 A, 318/254, 318/439, 318/257, 318/281, 318/287, 318/291, 318/293, 318/696, 318/599, 363/16, 363/17, 363/98
• US Class Current: 318/400.01
• CPC Class Codes: H02K 29/08 using magnetic effect devices, e.g. Hall-plates, magneto-resistors H02K29/12 takes precedence
• CPC Class Codes: H02P 2209/07 Trapezoidal waveform
• CPC Class Codes: H02P 6/06 Arrangements for speed regulation of a single motor wherein the motor speed is measured and compared with a given physical value so as to adjust the motor speed

Abstract

A direct current brushless electric motor has a rotor, and a stator with inwardly extending teeth, between each pair of which a winding slot is defined. The radially inward face of each tooth has a dummy slot shaped so the reluctance forces between rotor and stator due to the presence of the dummy slots are the same as those due to the winding slots. Motor control means incorporate a current feedback loop based on the incoming phase of each phase combination in the phase energization sequence in a driving mode and phase changeover may be initiated by Hall devices, two for each transition point, underlying the axial ends of the rotor magnets. The control means may incorporate a pulse width modulation power supply permitting the establishment of bias currents under motor standstill conditions.

Claims

1. A brushless d.c. drive system, comprising a multiphase motor having a stator, a rotor and a plurality of phase windings;

control means for energizing said phase windings in paired combinations and in a predetermined sequence during system operation, two phase windings being energized in each paired combination;

sensor means for indicating rotor disposition at each of a plurality of rotational dispositions of the rotor relative to the stator, each said disposition corresponding to a transition from energization of one said paired combination of the phase windings of the motor to energization of a further paired combination of the phase windings, one of the phase windings of a paired combination of phase windings energized prior to each said transition being de-energized at said transition and a further winding being energized at said transition to define a new paired combination of phase windings, and the energization of the other of said phase windings of said paired combination of phase windings energized prior to said transition being maintained through said transition and subsequent thereto in said new paired combination;

current sample means for providing a signal indicative of the actual current present in each phase winding;

means for establishing a current error signal by comparison of a required current signal with said signal indicative of actual current present in one of the phase windings of an energized paired combination of phase windings;

means for regulating the current flowing in the phase windings, when energized, in dependence on said current error signal; and

means for transferring the establishment of said current error signal from comparison of said required current signal with said signal indicative of actual current present in the phase winding whose energization is maintained at each said transition from one said paired combination of phase windings to another of said paired combinations of phase windings, to comparison of said required current signal with said signal indicative of actual current present in the phase winding being energized at said transition, the current present in said phase winding being energized being, at least initially, substantially zero, so that the current error signal is, at least initially, of relatively large magnitude, and thus demands a large phase current.

2. A brushless d.c. drive system, comprising a multiphase motor having a stator, a rotor, and a plurality of phase windings;

control means for energizing said phase windings in paired combinations and in a predetermined sequence during system operation, two phase windings being energized in each paired combination;

sensor means for indicating rotor disposition at each of a plurality of rotational dispositions of the rotor relative to the stator, each said disposition corresponding to a transition from energization of one said paired combination of the phase windings of the motor to energization of a further paired combination of the phase windings, one of the windings of a paired combination of phase windings energized prior to each said transition being de-energized at said transition and a further winding being energized at said transition to define a new paired combination of phase windings, and the energization of the other of said phase windings of said paired combination of phase windings energized prior to said transition being maintained through said transition and subsequent thereto in said new paired combination;

current sampling means for providing a signal indicative of the actual current present in each phase winding;

means for establishing a current error signal by comparison of a required current signal with said signal indicative of actual current present in one of the phase windings of an energized paired combination of phase windings;

means for regulating the current flowing in the phase windings, when energized, in dependence on said current error signal; and

the system also comprising rotor speed monitoring means for providing a signal indicative of rotor speed and means responsive to said rotor speed signal for transferring, when rotor speed is less than a predetermined value, the establishment of said current error signal from comparison of said required current error signal with said signal indicative of actual current present in the phase winding whose energization is maintained at each said transition from one said paired combination of phase windings to another of said paired combination of phase windings, to comparison of said required current signal with said signal indicative of actual current present in the phase winding being energized at said transition, and, when rotor speed is equal to or greater than said predetermined value, for transferring the establishment of said current error signal from comparison of said required current signal with said signal indicative of actual current present in the phase winding being de-energized at each said transition from one said paired combination of phase windings to another of said paired combinations of phase windings, to comparison of said required signal with said signal indicative of actual current present in the phase winding whose energization is maintained at said transition, so that the current error signal is of relatively small magnitude and initial phase current overshoot is substantially minimized when rotor speed is equal to or greater than said predetermined value.

3. A brushless d.c. drive system, comprising a multiphase motor having a stator, a rotor and a plurality of phase windings;

control means for energizing said phase windings in paired combinations and in a predetermined sequence during system operation, two phase windings being energized in each paired combination;

sensor means for indicating rotor disposition at each of a plurality of rotational dispositions of the rotor relative to the stator, each said disposition corresponding to a transition from energization of one said paired combination of the phase windings of the motor to energization of a further paired combination of the phase windings, one of the phase windings of a paired combination of phase windings energized prior to each said transition being de-energized at said transition and a further winding being energized at said transition to define a new paired combination of phase windings, and the energization of the other of said phase windings of said paired combination of phase windings energized prior to said transition being maintained through said transition and subsequent thereto in said new paired combination;

current sample means for providing a signal indicative of the actual current present in each phase winding;

means for establishing a current error signal by comparison of a required current signal with said signal indicative of actual current present in one of the phase windings of an energized paired combination of phase windings;

means for regulating the current flowing in the phase windings, when energized, in dependence on said current error signal;

the motor having four torque/speed operating quadrants, and the system also comprising means for transferring, for predetermined regions of the torque/speed operating quadrants of the motor, the establishment of said current error signal from comparison of said required current error signal with said signal indicative of actual current present in the phase winding whose energization is maintained at each said transition from one said paired combination of phase windings to another of said paired combinations of phase windings, to comparison of said required current signal with said signal indicative of actual current present in the phase winding being energized at said transition, and, for other regions of said operating quadrants, for transferring the establishment of said current error signal from comparison of said required current signal with said signal indicative of actual current present in the phase winding being de-energized at each said transition from one said paired combination of phase windings to another of said paired combinations of phase windings, to comparison of said required signal with said signal indicative of actual current present in the phase winding whose energization is maintained at said transition.

4. A brushless d.c. drive system, comprising a multiphase rotational motor having a stator, a rotor and a plurality of phase windings, control means for energizing said phase windings in paired combination and in a predetermined sequence during system operation, and sensor means associated with said control means for indicating rotor disposition at each of a plurality of rotational dispositions of the rotor relative to the stator, each said disposition corresponding to a transition from energization of one said combination of the phase windings of the motor to energization of a further combination of the phase windings, one said winding being de-energized at each said transition and a further winding being energized, and the disposition of the rotor for transition between any two phase combination in one direction of rotation being rotationally displaced from its disposition for transition between the same two phase combinations in the opposite direction of rotation.

5. A drive system according to claim 4, wherein said sensor means includes two switch means for each said transition between energizations of phase combinations and said sensor indications are provided by changes of state of the switch means, one of each said two switch means undergoing a change of state when the rotor is in a first predetermined rotational disposition relative to the stator for determining changeover between the relevant phase combinations for one direction of rotation through the transition and the other of each said two switch means undergoing a change of state when the rotor is in a second predetermined rotational disposition relative to the stator for determining changeover between the same phase combinations for the opposite direction of rotation.

6. A drive system according to claim 5, wherein the rotational disposition of the rotor for a change of state of said one switch means of said two switch means associated with each said transition and its rotational disposition for a change of state of said other switch means of said two switch means are separated by shorter and longer angular increments of rotation, said shorter angular increment of rotation defining a phase transition region, and the system includes inhibit means for preventing said control means from initiating changeover between phases on leaving said phase transition region when the direction of rotation of the rotor is reversed while the rotational disposition of the rotor is within said phase transition region.

7. A brushless d.c. motor, comprising a stator having a plurality of windings and formed from a multiplicity of laminations, and a rotor having a plurality of poles defined by axially extending permanent field magnets, the rotor being rotationally mounted within the stator and being substantially surrounded by the stator, a plurality of Hall effect devices being mounted on the stator at one axial end of the motor and positioned at a plurality of locations around a circumferential path in the vicinity of axial end regions of said axially extending permanent field magnets, said axially extending permanent field magnets serving also as triggering magnets for the Hall effect devices, and each of said devices being activated when there is a respective predetermined angular relationship between the rotor and the stator, the stator laminations having axially outwardly directed axial end faces, and the axial end regions of the axially extending permanent field magnets having axially outwardly directed axial end faces, the axial end face of the stator lamination at the axial end of the motor at which the Hall effect devices are mounted and the axial end faces of the permanent magnet axial end regions at said axial end of the motor being disposed in a substantially common radial plane extending at right angles to the axis of rotation of the rotor, the windings having winding end portions extending axially outwardly of said stator lamination axial end face at said axial end of the motor at which the Hall effect devices are mounted so that annular space is defined radially inwardly of the winding end portions and axially outwardly of the axial end faces of the axially extending permanent field magnet end regions, mounting means for the Hall effect devices extending through said annular space to support said Hall effect devices in dispositions which are radially inwardly of and underlie said axial end regions of said axially extending permanent field magnets.

8. A brushless d.c. motor comprising a stator having a plurality of windings and formed from a multiplicity of laminations, and a rotor having a plurality of poles defined by axially extending permanent field magnets, the rotor being rotationally mounted within the stator and being substantially surrounded by the stator, a plurality of Hall effect devices being mounted on the stator at one axial end of the motor and positioned at a plurality of locations around a circumferential path in the vicinity of axial end regions of said axially extending permanent field magnets, said axially extending permanent field magnets serving also as triggering magnets for the Hall effect devices, and each of said devices being activated when there is a respective predetermined angular relationship between the rotor and the stator, the stator lamiantions having axially outwardly directed axial end faces, and the axial end regions of the axially extending permanent field magnets having axially outwardly directed axial end faces, the axial end face of the stator lamination at the axial end of the motor at which the Hall effect devices are mounted and the axial end faces of the permanent magnet axial end regions at said axial end of the motor being disposed in a substantially common radial plane extending at right angles to the axis of rotation of the rotor, the windings having winding end portions extending axially outwardly of said stator lamination axial end face at said axial end of the motor at which the Hall effect devices are mounted so that an annular space is defined radially inwardly of the winding end portions and axially outwardly of the axial end faces of the axially extending permanent field magnet end regions, mounting means for the Hall effect devices extending through said annular space to support said Hall effect devices in dispositions which are radially inwardly of and underlie said axial end regions of said axially extending permanent field magnets, said rotor having a generally cylindrical rotor core, said generally cylindrical rotor core having a first full diameter portion and an axial end portion of lesser diameter than said first full diameter portion, said lesser diameter axial end portion of the rotor core extending axially from on axial end of said first full diameter portion at said axial end of the motor at which the Hall effect devices are mounted, said axially extending permanent field magnets being mounted on the exterior of said first full diameter portion of said generally cylindrical rotor core and extending axially beyond said one axial end of said first full diameter portion of said generally cylindrical rotor core, so that the axial end regions of said axially extending permanent field magnets are radially spaced from said lesser diameter axial end portion of said generally cylindrical rotor core, an annular space being therefore defined radially inwardly of the axial end regions of the permanent field magnets and between the magnets and the lesser diameter axial end portion of the rotor core, and the Hall effect devices being located within said annular space.

9. A pulse width modulation power suppply for a two-terminal inductive load, having two switches and control means for regulating the on and off periods of each switch to control current magnitude and direction in said load, the on period of each switch being phase displaced relative to the on period of the other switch under zero net current conditions and of sufficient duration for overlap periods to be established between the on periods of the switches, a forward current pulse being established by a first said overlap period and a reverse current pulse being established by a second said overlap period, so that equal and opposite alternating current pulses flow through said load under said zero net current conditions.

10. A pulse width modulation power supply for a two-terminal bidirectional inductive load, having four switches and control means for regualting the on and off periods of each switch to control current magnitude and direction in said load, the on period of each of said switches being phase displaced relative to the on period of an associated one of said switches under zero net current conditions and of sufficient duration for overlap periods to be established between the on periods of said associated switches, a forward current pulse being established by a first said overlap period and a reverse current pulse being established by a second said overlap period, so that equal and opposite alternating current pulses flow through said load under said zero net current conditions.

11. A power supply according to claim 10, wherein said two-terminal bidirectional inductive load is a motor winding.

12. A pulse width modulation power supply for a three-phase motor having three phase windings, comprising a six switch bridge and control means for regulating the on and off periods of each switch to control current magntidue and direction in each phase winding, each instantaneously active group of four switches together with the control means substantially instantaneously defining a power supply for one of said phase windings, the on period of each of said switches of said instantaneously active group being phase displaced relative to the on period of an associated one of said switches of said group under zero net current conditions for said one of said phase windings and of sufficient duration for overlap periods to be established between the on periods of said associated switches, a forward current pulse being established by a first said overlap period and a reverse current pulse being established by a second said overlap period, so that equal and opposite alternating current pulses flow through said one of said phase windings under said zero net current conditions.

13. A brushless d.c. drive system, comprising a three phase rotational motor having a stator, a plurality of phase windings located on said stator, a rotor, and a plurality of permanent magnets mounted on said rotor, control means for energizing the phase windings of the motor, and means for applying a signal indicative of a parameter of motor performance to said control means, said control means including means for connecting the phase windings of said motor either for energization in paired combinations or for single-phase energization, in dependence on said motor performance parameter, without interruption of motor rotation, said control means being adapted to energize said windings, in each case, in a respective predetermined sequence, and said phase windings connecting means of the control means being adapted to connect said phase windings for energization in paired combinations at low motor speeds.

14. A brushless d.c. drive system comprising a three phase rotational motor, control means for energizing the phase windings of the motor, and means for applying a signal indicative of a parameter of motor performance to said control means, said control means including means for connecting the phase windings of said motor either for energization in paired combinations or for single-phase energization, in dependence on said motor performance parameter, without interruption of motor rotation, and said control means being adapted to energize said windings, in each case, in a respective predetermined sequence, wherein said parameter of motor performance is speed, the system includes means for monitoring motor speed, and the control means includes a comparator for detecting whether or not motor speed exceeds a preset speed to provide an input to said means for connecting the phase windings either for energization in paired combinations or for single-phase energization so that said phase windings are connected for energization in paired combinations when motor speed is less than said preset speed and are connected for single-phase energization when motor speed exceeds said preset speed.

15. A brushless d.c. drive system comprising a multiphase motor having a stator, a rotor and a plurality of phase windings;

control means for energizing said phase windings in paired combinations and in a predetermined sequence during system operation, two phase windings being energized in each paired combination;

sensor means for indicating rotor disposition at each of a plurality of rotational dispositions of the rotor relative to the stator, each said disposition corresponding to a transition from energization of one said paired combination of the phase windings of the motor to energization of a further paired combination of the phase windings, one of the phase windings of a paired combination of phase windings energized prior to each said transition being de-energized at said transition and a further winding being energized at said transition to define a new paired combinatiod of phase windings, and the energization of the other of said phase windings of said paired combination of phase windings energized prior to said transition being maintained through said transition and subsequent thereto in said new paired combination;

current sample means for providing a signal indicative of the actual current present in each phase winding;

means for establishing a current error signal by comparison of a required current signal with said signal indicative of actual current present in one of the phase windings of an energized paired combination of phase windings;

means for regulating the current flowing in the phase windings, when energized, in dependence on said current error signal; and

means for transferring the establishment of said current error signal from comparison of said required current signal with said signal indicative of actual current present in the phase winding whose energization is maintained at each said transition from one said paired combination of phase windings to another of said paired combinations of phase windings, to comparison of said required current signal with said signal indicative of actual current present in the phase winding being energized at said transition, the current present in said phase winding being energized being, at least initially, substantially zero, so that the current error signal is, at least initially, of relatively large magnitude, and thus demands a large phase current, wherein the stator has a plurality of winding slots and the rotor has a plurality of poles, the stator having at least one dummy slot between at least oen pair of adjacent winding slots, and said at least one dummy slot being dimensioned so that during relative rotation of the rotor and stator, the reluctance force prevailing between the rotor and stator due to the presence of said at least one dummy slot is of the same order of magnitude as the reluctance force prevailing therebetween due to the presence of a winding slot, said at least one dummy slot behaving similarly to a winding slot in respect of reluctance torque.

16. A brushless d.c. drive system according to claim 15, wherein the stator has at least one dummy slot between each two adjacent winding slots.

17. A brushless d.c. drive system comprising a multiphase motor having a stator, a rotor and a plurality of phase windings;

control means for energizing said phase windings in paired combinations and in a predetermined sequence during system operation, two phase windings being energized in each paired combination;

sensor means for indicating rotor disposition at each of a plurality of rotational dispositions of the rotor relative to the stator, each said disposition corresponding to a transition from energization of one said paired combination of the phase windings of the motor to energization of a further paired combination of the phase windings, one of the phase windings of a pair combination of phase windings energized prior to each said transition being de-enegized at said transition and a further winding being energized at said transition to define a new paired combination of phase windings, and the energization of the other of said phase windings of said paired combination of phase windings energized prior to said transition being maintained through said transition and subsequent thereto in said new paired combination;

current sample means for providing a signal indicative of the actual current present in each phase winding;

means for establishing a current error signal by comparison of a required current signal with said signal indicative of actual current present in one of the phase windings of an energized paired combination of phase windings;

means for regulating the current flowing in the phase windings, when energized, in dependence on said current error signal; and

means for transferring the establishment of said current error signal from comparison of said required current signal with said signal indicative of actual current present in the phase winding whose energization is maintained at each said transition from one said paired combination of phase windings to another of said paired combinations of phase windings, to comparison of said required current signal with said signal indicative of actual current present in the phase winding being energized at said transition, the current present in said phase winding being energized being, at least initially, substantially zero, so that the current error signal is, at least initially, of relatively large magnitude, and thus demands a large phase current, wherein the stator has a plurality of winding slots and the rotor has a plurality of poles, the stator having two dummy slots between at least one pair of adjacent winding slots, and each said dummy slot being dimensioned so that during relative rotation of the rotor and stator, the reluctance forces prevailing between the rotor and stator due to the presence of said dummy slots are of the same order of magnitude as the reluctance forces prevailing therebetween due to the presence of the winding slots, said dummy slots behaving similarly to the winding slots in respect of reluctance torque.

18. A brushless d.c. drive system according to claim 17, wherein the stator has two dummy slots between a pair of adjacent winding slots at a plurality of locations equally spaced around the stator.

19. A brushless d.c. drive system according to claim 18, wherein the winding and dummy slots are spaced around the stator so that the angular spacing between any two adjacent slots is the same.

20. A brushless d.c. drive system according to claim 18, wherein the winding slots for each phase within an angular stator increment corresponding to an electrical cycle are spaced so that the phases are equally spaced electrically within each electrical cycle.

21. A brushless d.c. drive system according to claim 20, wherein the angular spacing between the winding slot of successive phases within each pole pitch corresponds to 120 degrees electrical.

22. A brushless d.c. motor, comprising a stator having a plurality of windings, a rotor having a plurality of axially extending permanent field magnets mounted thereon, said stator and said rotor being coaxially disposed and relatively rotatable and one of said field windings and said field magnets being radially outward of the other of said windings and said field magnets, and a plurality of Hall effect devices being mounted on the stator and positioned at a plurality of locations around a circumferential path, said Hall effect devices being disposed at one aixal end of the rotor, axially inward of the end regions of said field magnets, and on the opposite radial side of said field magnets from said windings, and each of said devices being activated when there is a respective predetermined angular relationship between the rotor and the stator, and each of said Hall effect devices being disposed directly against a steel flux return ring, said ring being located on the opposite radial sides of said devices from said field magnets, for intensifying the field strength on said radially opposite sides of the devices from said field magnets.

23. A brushless d.c. drive system, comprising a multiphase motor having a stator, a rotor and a plurality of phase windings;

control means for energizing said phase windings in paired combinations and in a predetermined sequence during system operation, two phase windings being energized in each paired combination;

sensor means for indicating rotor disposition at each of a plurality of rotational dispositions of the rotor relative to the stator, each said disposition corresponding to a transition from energization of one said paired combination of the phase windings of the motor to energization of a further paired combination of the phase windings, one of the phase windings of a paired combination of phase windings energized prior to each said transition being de-energized at said transition and a further winding being energized at said transition to define a new paired combination of phase windings, and the energization of the other of said phase windings of said paired combination of phase windings energized prior to said transition being maintained through said transition and subsequent thereto in said new paired combination;

current sample means for providing a signal indicative of the actual current present in each phase winding;

means for establishing a current error signal by comparison of a required current signal with said signal indicative of actual current present in one of the phase windings of an energized paired combination of phase windings, when energized, in dependence on said current erro signal; and

means for transferring the establishment of said current error signal from comparison of said required current signal with said signal indicative of actual current present in the phase winding whose energization is maintained at each said transition from one said paired combination of phase windings to another of said paired combiantions of phase windings, to comparison of said required current signal with said signal indicative of actual current present in the phase winding being energized at said transition, the current present in said phase winding being energized being, at least initially, substantially zero, so that the current error signal is, at least initially, of relatively large magnitude, and thus demands a large phase current, wherein the stator has a plurality of winding slots and the rotor has a plurality of poles, the stator having two dummy slots between at least one pair of adjacent winding slots and two dummy slot between at least one other pair of adjacent winding slots, each said dummy slot being dimensioned so that during relative rotation of the rotor and stator, the reluctance forces prevailing between the rotor and stator due to the presence of said dummy slots are the same order of magnitude as the reluctance forces prevailing therebetween due the presence of the winding slots, said dummy slots behaving similarly to the winding slots in respect of reluctance torque.

24. A brushless d.c. drive system according to claim 23, wherein the stator has two dummy slots between a pair of adjacent winding slots at a plurality of locations equally spaced around the stator and one dummy slot between each pair of adjacent winding slots not having two dummy slots therebetween.

25. A brushless d.c. drive system according to claim 24, wherein the winding and dummy slots are spaced around the stator so that the angular spacing between any two adjacent slots is the same.

26. A brushless d.c. drive system according to claim 24, wherein the winding slots for each phase within an annular stator increment corresponding to an electrical cycle are spaced so that the phase are equally spaced electrically within each electrical cycle.

27. A brushless d.c. drive system according to claim 26, wherein the angular spacing between the winding slots of successive phases within each pole pitch corresponds to 120°

electrical.