Abstract: A rotor for a reluctance type rotating machine includes a rotor core formed by stacking a number of annular core materials each of which includes magnetic concave and convex portions. The rotor core has two keys which are formed at two positions on an inner circumference of the rotor core. The positions are spaced 180 degrees apart from each other with respect to the rotor core. The rotor core is divided into a plurality of blocks and the core materials constituting at least one block have the magnetic concave and convex portions shifted by a predetermined angle relative to the core materials constituting the other or another block on the basis of a center line passing through the keys. A whole or part of the core materials of at least one block are located circumferentially 180 degrees apart form the core materials constituting the other or another block.

Abstract: A spoke permanent magnet rotor that includes a shaft defining a rotor axis. A first non-magnetic end portion is coupled to the shaft and a ferromagnetic pole piece defines an aperture therethrough. A second non-magnetic end portion is positioned to dispose the pole piece between the first end portion and the second end portion. A portion of one of the first end portion and the second end portion extends through the aperture and bonds with the other of the first end portion and the second end portion.

Abstract: An electrical machine having a machine output rating. The electrical machine including a shaft rotatable about an electrical machine axis, a rotor coupled to the shaft and rotating with the shaft, and a stator including a stator core. The rotor is configurable to include a first rotor portion having a relation to a first output rating and a second rotor portion having a relation to a second output rating. The stator core is configurable to be disposed adjacent to the first rotor portion relative to the machine axis when the machine output rating corresponds to the first output rating and adjacent to the second rotor portion when the machine output rating corresponds to the second output rating.

Abstract: A magnet motor with rotor assembly is provided that has a plurality of magnet members that circumscribe a wall of the rotor core or stator in an orientation that minimizes or eliminates gaps therebetween. The magnet members can have non-parallel opposing sides to allow for elimination of the gaps. The magnet members may have trapezoidal-like shapes.

Abstract: A polyphasie multi-coil generator includes a drive shaft, at least first and second rotors rigidly mounted on the drive shaft so as to simultaneously synchronously rotate with rotation of the drive shaft, and at least one stator sandwiched between the first and second rotors. A stator array on the stator has an array of coils mounted to the stator in a first angular orientation about the drive shaft. The rotors each have an array of magnets which are equally circumferentially spaced around the rotor and located at the same radial spacing with respect to the center of the rotor and the drive shaft. The arrays of magnets on adjacent rotors are off-set by an angular off-set relative to one another.

Abstract: A rotor for motor is disclosed to have a plurality of protruding portions arranged in two rows around the periphery of the body thereof and spaced by magnetic gaps, and a plurality of magnets of semicircular cross section respectively covered on the protruding portions and respectively abutted with one end of each of the magnets at one row against two adjacent magnets at the other row.

Abstract: A permanent-magnet rotating machine includes a rotor having a rotor core carrying on a curved outer surface multiple permanent magnets arranged in two rows along an axial direction. The permanent magnets in one row are skewed from those in the other row in a circumferential direction by a row-to-row skew angle (electrical angle) ?e. A stator having a tubular stator core in which the rotor disposed includes stator coils for producing a rotating magnetic field for rotating the rotor. A lower limit of the row-to-row skew angle ?e larger than 30 degrees (electrical angle). A ratio of cogging torque occurring in the absence of skew to cogging torque occurring when the permanent magnets are skewed, at a row-to-row skew angle of 30 degrees is calculated based on the cogging torque ratio, the row-to-row skew angle ?e, and B-H curve properties of the stator core.

Abstract: The disclosure describes a DC motor including a rotor unit arranged within the motor body and has a cylindrical field magnet fixed to an outer surface of a holder. The holder has a rotating shaft press-fitted through the center, and the cylindrical field magnet has the S and the N poles alternately around a circumference. There is a stator unit which is circumferentially arranged around the rotor unit, that is made of a plurality of stator yokes that are arranged so that they oppose the field magnet through a small gap. Each of the stator yokes is formed by circumferentially stacking a large number of thin plates, each consisting of a salient pole, and a number of coil units, each formed by winding a magnet wire on a bobbin, and mounting the bobbins on the stator yokes. In the described arrangement, each of the S and N poles has a plurality of stages formed in an axial direction and shifted from each other in the circumferential direction by a predetermined shift amount with respect to the field magnet.

Abstract: A permanent magnet rotating machine includes a rotor with a permanent magnet having circumferential magnetic poles with a skew at boundaries between magnetic poles of the permanent magnet, and a stator having a stator iron core in an almost cylindrical shape and convex poles protruding inwardly, the rotor being disposed within the stator. A skew angle of the skew is smaller than a theoretical angle ?s (electrical angle) and larger than one-half the theoretical angle ?s, wherein the theoretical angle ?s is defined as, ?s=180×(number of magnetic poles in the rotor)/smallest integer of which both the number of magnetic poles in the rotor and the number of magnetic poles in the stator are factors) [deg.].

Abstract: An electric motor, particularly an electronically commutated direct current motor, has a stator and a rotor. The stator and the rotor are arranged coaxially to a longitudinal axis of the electric motor. The stator features a plurality of electrical stator poles and a plurality of phase windings. The rotor features a permanent magnet with a least one magnetic pole pair which is dedicated to the phase windings. The phase windings and/or the permanent magnet are divided into several axial sections in the direction of the longitudinal axis of the electric motor and these sections are staggered around the longitudinal axis of the electric motor with respect to each other. Angular positions of the individual phases are offset with respect to each other is in such a way that torque ripple can be reduced and torque gaps can be prevented.

Abstract: A magnetic motor includes rotors having permanent magnets and rotatably disposed around a rotating axis, a magnetic sensor disposed at a periphery of the rotors and a plurality of electro-magnetic coils, and control means which controls electric current to the coils based on detection of magnetism from the magnets by means of the sensor. The rotor is equidistantly divided in a circumferential direction into the same number of regions as that of the coils. Each region includes a portion wherein a plurality of magnets are disposed in a circumferential direction and a portion wherein no magnets are disposed. Each magnet is disposed inclined against a radial line extending outwardly from the rotating axis. The control means switches the direction of electric current to the coils based on the signal from the sensor and supplies current after a lapse of predetermined time from the detection of magnetism by the sensor.

Abstract: A magneto generator for self-powered apparatuses; the magneto generator comprises a stator provided with an electric winding, and a permanent magnet rotor coaxially arranged to the stator. The stator and the rotor have a first, and respectively a second pole system which together with the electric winding define a multiphase electromagnetic system connected to a bridge rectifier, secured to the stator. The poles of the stator and the poles of the rotor have opposite polar surfaces in which the axis of each polar surface of the rotor, is slanted with respect to a reference line parallel to the longitudinal axes of the polar surfaces of the stator.

Abstract: An electrical machine comprises a stator and a rotor. The rotor includes a plurality of stator teeth and a winding with compact coils disposed on the teeth. The winding has (m) phases and (p) poles; where (m) is an integer and is greater than or equal to two; where (p) is an integer, is greater than or equal to two, and is an even number. The rotor has a magnetization pattern including a magnetization skew. In some constructions, each stator includes one or more channels along a surface adjacent to the rotor. The channels can be of various shapes including a trapezoidal shape or a curvilinear shape.

Abstract: Rotor assembly for an electrical machine, wherein a body of generally cylindrical shape having an inner opening for coaxially mounting the body on a shaft, permanent magnets embedded in said body, wherein at least one of the permanent magnets is split in at least two magnet sections which extend from about the inner opening towards the outer periphery of the body and are inclined towards a plane, which extends in a radial direction of the body.

Abstract: A brushless DC permanent magnet motor having a step skewed rotor including a rotor shaft having a portion having a substantially uniform cross sectional configuration defined by N planar sides of substantially equal length and width wherein N is equal to the number of poles of the motor, first and second annular sets of N number of substantially identically shaped bread loaf magnets one of which is attached to each of the N planar sides of the rotor shaft wherein the magnets of the first set have their orientation reversed with respect to the magnets of the second set and the magnets of the first set are offset or skewed by a predetermined skew angle from the magnets of the second set of magnets to form a stepped skewed rotor.

Abstract: A permanent magnet motor having a rotor with permanent magnets disposed on the outer circumferential face at a predetermined interval in a peripheral direction, and a stator with magnetic pole pieces arranged at a predetermined spacing in the peripheral direction, the magnetic pole pieces being opposed to the permanent magnets, the stator surrounding the rotor, wherein auxiliary grooves are provided on a face of each magnetic pole piece of the stator opposed to the permanent magnets of the rotor, and a skew having an electric angle in a range of 61° to 84° is provided relatively between the rotor and the stator.

Abstract: Several embodiments of rotating electrical machines where cogging torque is reduced as well as the distortion of the back emf and improve torque characteristic with reduced torque ripples by dividing either the permanent magnets and/or the poles of the coil windings in axially separated portions that are circumferentially shifted relative to each other.

Abstract: To provide a motor which can suppress vibration and noise during an operation of a concentrated winding motor and can achieve low vibration and low noise with high efficiency. Skew is formed on at least one of a stator (10) provided with concentrated windings and a rotor (20), and the windings (13—13) of different phases in a groove (19) for windings are brought into contact with each other directly or via an insulating material.

Abstract: An electrical machine having a machine output rating. The electrical machine including a shaft rotatable about an electrical machine axis, a rotor coupled to the shaft and rotating with the shaft, and a stator including a stator core. The rotor is configurable to include a first rotor portion having a relation to a first output rating and a second rotor portion having a relation to a second output rating. The stator core is configurable to be disposed adjacent to the first rotor portion relative to the machine axis when the machine output rating corresponds to the first output rating and adjacent to the second rotor portion when the machine output rating corresponds to the second output rating.

Abstract: A permanent magnet motor to reduce torque ripple includes a rotor having at least three segments. Each of the three segments is formed sequentially adjacent and aligned along an axis of the rotor. Each segment has at least one pair of permanent magnets disposed at a substantially equal interval in a peripheral direction of the rotor. First and second segments are skewed relative to each other by a first angular displacement, and the first and third segments are skewed relative to each other by a second angular displacement. The first and second angular displacements are selected to cause a net sum of torque ripple produced by each of the segments to be substantially equal to zero during an operation of the motor.

Abstract: A motor providing unidirectional rotational motive power is provided. The motor has a generally circular stator with a stator axis, an outer surface, and a circumferential line of demarcation at about a midpoint of the outer surface. The motor also includes one or more stator magnets attached to the outer surface of the stator. The stator magnets are arranged in a generally circular arrangement about the stator axis and generate a first magnetic field. An armature is attached to the stator for rotation therewith, the armature having an axis parallel to the stator axis. One or more rotors, are spaced from the armature and coupled thereto by an axle for rotation about an axis of each rotor, each rotor rotating in a plane generally aligned with the armature axis. Each rotor includes one or more rotor magnets, with each rotor magnet generating a second magnetic field.

Abstract: The present invention minimizes variations in torque due to cogging in a permanent magnet brushless electric motor and, among other things, specifies a topology of a rotor and a stator in relation to one another. According to one embodiment, a permanent magnetic motor includes a housing surrounding a stator that in turn surrounds a rotor rotatably mounted to the housing. The stator has a stator cross section including a plurality of uniformly distributed and spaced apart stator poles separated by slots. The stator poles extend radially inward from the inner surface and terminate at an end defined by an inner pole face. Each end is separated from an adjacent end by a distance defined as a stator slot width W. The rotor cross section includes a plurality of spaced apart permanent magnets carried by the shaft and angularly and uniformly distributed about the shaft.

Abstract: A permanent magnet motor having a rotor with permanent magnets disposed on the outer circumferential face at a predetermined interval in a peripheral direction, and a stator with magnetic pole pieces arranged at a predetermined spacing in the peripheral direction, the magnetic pole pieces being opposed to the permanent magnets, the stator surrounding the rotor, wherein the auxiliary grooves are provided on a face of each magnetic pole piece of the stator opposed to the permanent magnets of the rotor, and a skew having an electric angle of 72° is provided relatively between the rotor and the stator.

Abstract: A magneto generator for self-powered apparatuses; the magneto generator comprises a stator provided with an electric winding, and a permanent magnet rotor coaxially arranged to the stator. The stator and the rotor have a first, and respectively a second pole system which together with the electric winding define a multiphase electromagnetic system connected to a bridge rectifier, secured to the stator. The poles of the stator and the poles of the rotor have opposite polar surfaces in which the axis of each polar surface of the rotor, is slanted with respect to a reference line parallel to the longitudinal axes of the polar surfaces of the stator.

Abstract: A permanent magnet motor to reduce torque ripple includes a rotor having at least three segments. Each of the three segments is formed sequentially adjacent and aligned along an axis of the rotor. Each segment has at least one pair of permanent magnets disposed at a substantially equal interval in a peripheral direction of the rotor. First and second segments are skewed relative to each other by a first angular displacement, and the first and third segments are skewed relative to each other by a second angular displacement. The first and second angular displacements are selected to cause a net sum of torque ripple produced by each of the segments to be substantially equal to zero during an operation of the motor.

Abstract: A capstan motor for a magnetic recording and reproducing apparatus includes a stator having a coil disposed on outer peripheral direction thereof, and a rotor having a magnet to correspond to coil and rotated by an electromagnetic interaction between the coil and the magnet. A capstan shaft is rotated integrally with the rotor, is fixed on the rotor and installed so that one side of the capstan shaft is cohered with a pinch roller taking a tape therebetween to drive the tape with the pinch roller. The magnet has a predetermined shape and is provided to apply magnetic force of the magnet eccentrically for an electromagnetic force generated on the coil so that a predetermined thrust can be applied to the capstan shaft toward one direction between upper and lower directions of the shaft direction.

Abstract: An electric motor, particularly an electronically commutated direct current motor, has a stator and a rotor. The stator and the rotor are arranged coaxially to a longitudinal axis of the electric motor. The stator features a plurality of electrical stator poles and a plurality of phase windings. The rotor features a permanent magnet with a least one magnetic pole pair which is dedicated to the phase windings. The phase windings and/or the permanent magnet are divided into several axial sections in the direction of the longitudinal axis of the electric motor and these sections are staggered around the longitudinal axis of the electric motor with respect to each other. Angular positions of the individual phases are offset with respect to each other is in such a way that torque ripple can be reduced and torque gaps can be prevented.

Abstract: A brushless DC permanent magnet motor having a step skewed rotor including a rotor shaft having a portion having a substantially uniform cross sectional configuration defined by N planar sides of substantially equal length and width wherein N is equal to the number of poles of the motor, first and second annular sets of N number of substantially identically shaped bread loaf magnets one of which is attached to each of the N planar sides of the rotor shaft wherein the magnets of the first set have their orientation reversed with respect to the magnets of the second set and the magnets of the first set are offset or skewed by a predetermined skew angle from the magnets of the second set of magnets to form a stepped skewed rotor.

Abstract: Several embodiments of rotating electrical machines where cogging torque is reduced as well as the distortion of the back emf and improve torque characteristic with reduced torque ripples by dividing either the permanent magnets and/or the poles of the coil windings in axially separated portions that are circumferentially shifted relative to each other.

Abstract: A motor for reducing torque ripple includes a shaft having a shaft axis, a rotor positioned about the shaft, a first magnet ring positioned on the rotor, the first magnet ring having magnets each occupying a magnet angle &egr; on the rotor, and a second magnet ring positioned on the rotor, the second magnet ring having magnets each occupying a magnet angle &egr; on the rotor, wherein the second magnet ring is shifted a non-zero number of degrees relative to the first magnet ring and wherein ends of each magnet within the second magnet ring are located at different angular positions than ends of each magnet within the first magnet ring relative to the shaft axis of the shaft. The magnet angle &egr; is preferably an optimal magnet angle for minimizing cogging torque and line to line back emf harmonics.

Abstract: A permanent-magnet rotating machine includes a rotor having a rotor core carrying on its curved outer surface multiple permanent magnets arranged in two rows along an axial direction in such a manner that the permanent magnets in one row are skewed from those in the other row in a circumferential direction by a row-to-row skew angle (electrical angle) &thgr;e, and a stator having a cylindrical stator core in which the rotor is disposed, the stator core being provided with stator coils for producing a rotating magnetic field for rotating the rotor. A lower limit of the row-to-row skew angle &thgr;e is set at a value larger than 30 degrees (electrical angle).

Abstract: A rotary electromechanical device includes a first motor including a first stator and a first rotor, a second motor including a second stator and a second rotor, and variable power supplies for driving the respective motors independently of each other, The motors are arranged in series along the axial direction of a rotary shaft. Magnetic poles of the same polarity of the rotors are located at uniform angular positions around the rotary shaft while magnetic poles of the stator of the motor and magnetic poles of the stator of the second motor are displaced from each other in the circumferential direction of the rotary shaft.

Abstract: A motor having a stator and a rotor and wherein the stator has a plurality of stator poles is disclosed. Each of the plurality of stator poles is separated by a stator pole pitch. The rotor is concentrically disposed within the stator and at least one pair of magnets is mounted to the rotor. The at least one pair of magnets has at least one skewed side. Further, the rotor has a uniform variable air gap between an adjacent magnet. The magnet has inner and outer arcuate surfaces. The center of a circle describing the outside diameter of the magnet is off-centered from a circle describing an inside diameter of the magnet. Further, the at least one pair of magnets is skewed by at least one half of stator slot pitch.

Abstract: A rotary electric motor has a stator with a plurality of separate and ferromagnetically isolated electromagnet core segments disposed coaxially about an axis of rotation. Core materials such as a soft magnetically permeable medium that is amenable to formation of a variety of particularized shapes. The core segments are supported by a non-ferromagnetic structure. The rotor comprises a plurality of permanent magnets with surfaces that face an air gap separation from the stator, the surfaces having a common geometric configuration. The stator pole surface geometric configuration and the rotor magnet surface geometric configuration are skewed with respect to each other. The effect of this skewing arrangement is to dampen the rate of change of the magnitude of the cogging torque that is produced by the interaction between a rotor magnet and a pole of a non-energized stator electromagnet as the permanent magnet traverses its rotational path.

Abstract: A permanent magnet design includes a magnetic field that is skewed relative to a center line of the magnet body. One surface of the magnet is adapted to be mounted or supported on a motor assembly component such as the rotor. The other side of the magnet body includes at least one surface that is not aligned with the center line of the magnet body. When the magnet is supported on a motor component so that the magnet center line is aligned with the axis of rotation of the motor rotor, the magnetic field of the magnet is not aligned with the rotor axis.

Abstract: A permanent magnet electric machine with reduced cogging torque includes a plurality of axial rotor sections that are defined on a radially outer surface of a rotor. The axial rotor sections include a set of permanent magnets that are in an unmagnetized state and that have opposite edges that are aligned with an axis of the rotor. The axial rotor sections are rotationally offset such that the edges of the permanent magnets create stair step interfaces. The n sets of permanent magnets are magnetized using a magnetizing fixture. The permanent magnets have a generally rectangular shape and are preferably arc magnets or breadloaf magnets. The conductors of the magnetizing fixture are aligned with the stair step interfaces. A magnetic field induced in the permanent magnets is substantially reduced along the stair step interfaces.

Abstract: A fault tolerant electric motor for steering actuation is disclosed. In an exemplary embodiment, the motor includes a stator assembly having a first group of stator windings and a second group of stator windings, thereby forming a redundant pair of stator windings. The first and second groups of stator windings are located within opposite hemispheres of the stator assembly. A rotor assembly is rotatingly disposed within the stator assembly, and has a plurality of magnets disposed around the periphery of a rotor core. Each of the plurality of magnets is arranged into a pair of segments, one of which is shifted from the other with respect to an axis of rotation of the rotor assembly.

Abstract: An AC servo motor in which annular polar anisotropic magnets, formed by splitting an anisotropic magnet into two or more portions in an axial line direction, are used in a rotor. The magnetic poles of the split annular polar anisotropic magnets are disposed so as to be shifted by a predetermined angle &thgr;′ which is greater than a skew angle &thgr; determined based on the number of torque ripples per rotation of the rotor determined by the number of magnetic poles and the number of slots in a stator-side iron core. The predetermined angle &thgr;′ is the angle obtained after adding to the skew angle &thgr; a value which takes into consideration magnetic interference between the magnets. The invention provides an AC servomotor which can be controlled with high precision as a result of reducing cogging torque generated between the magnet and the stator-side iron core.

Abstract: To provide a motor which can suppress vibration and noise during an operation of a concentrated winding motor and can achieve low vibration and low noise with high efficiency. Skew is formed on at least one of a stator (10) provided with concentrated windings and a rotor (20), and the windings (13-13) of different phases in a groove (19) for windings are brought into contact with each other directly or via an insulating material.

Abstract: A permanent magnet electric motor for use in an elevator installation includes a stator and a rotor assembly. The rotor assembly has a frame on which are mounted at least two rings with permanent magnets. The rings are removably mounted and are laterally fixed together by a fastener that also radially aligns the rings. The number of similar rings used defines a rotor length in multiple values of the ring length. The rings can be shifted by a suitable magnetic angle to permit the generation of a skewing effect of the magnets which reduces or eliminates a cogging torque of the motor. The rotor assembly can be easily and quickly installed and/or removed in very small spaces, especially in elevator installations.

Abstract: A permanent magnet motor having a rotor with permanent magnets disposed on the outer circumferential face at a predetermined interval in a peripheral direction, and a stator with magnetic pole pieces arranged at a predetermined spacing in the peripheral direction, the magnetic pole pieces being opposed to the permanent magnets, the stator surrounding the rotor, wherein auxiliary grooves are provided on a face of each magnetic pole piece of the stator opposed to the permanent magnets of the rotor, and a skew having an electric angle of 72° is provided relatively between the rotor and the stator.

Abstract: A brushless DC motor including a stator having plural slots; and a rotor which has plural permanent magnets and is divided into three rotor blocks in a rotation axis direction, the three rotor blocks being layered so that the arrangement angles of the rotor blocks differ from each other by an amount of a mechanical angle in a rotary direction that is equivalent to one third of a pulsation period of cogging torque generated by the rotor and stator. A brushless DC motor including a rotor having plural magnetic poles provided at an equal pitch in a circumferential direction by mounting permanent magnets in magnet mounting holes; and a stator having plural slots arranged at an equal pitch in a circumferential direction.

Abstract: The invention concerns a rotating electric machine which includes a stator equipped with armature coils and a rotor mounted rotating inside the stator. The rotor having a series of magnets with alternating polarities juxtaposed with magnetic parts having magnetic resistance, respectively associated with the magnets. Each assembly of one magnet and one associated magnetic part defining a rotor pole wherein some of the poles have alternately, along a generally tangential direction, a magnet followed by its magnetic part and a magnet preceded by its magnetic part. The invention is applicable to motor vehicle alternators and AC starters.

Abstract: A rotational electric machine in which a rotor having different-polarity field magnets arranged alternately in a rotational direction is divided axially into two rotor portions so that the axial position of one of the two rotor portions is changed relative to that of the other in accordance with a direction of torque of the rotor or the phase of synthesized magnetic poles of the field magnets is changed relative to that of magnetic poles of the other rotor portion in accordance with a direction of torque of the rotor, and a vehicle loaded with the rotational electric machine.

Abstract: A permanent magnet design includes a magnetic field that is skewed relative to a center line of the magnet body. One surface of the magnet is adapted to be mounted or supported on a motor assembly component such as the rotor. The other side of the magnet body includes at least one surface that is not aligned with the center line of the magnet body. When the magnet is supported on a motor component so that the magnet center line is aligned with the axis of rotation of the motor rotor, the magnetic field of the magnet is not aligned with the rotor axis.

Abstract: A permanent magnet electric machine with reduced cogging torque includes a plurality of axial rotor sections that are defined on a radially outer surface of a rotor. The axial rotor sections include a set of permanent magnets that are in an unmagnetized state and that have opposite edges that are aligned with an axis of the rotor. The axial rotor sections are rotationally offset such that the edges of the permanent magnets create stair step interfaces. The n sets of permanent magnets are magnetized using a magnetizing fixture. The permanent magnets have a generally rectangular shape and are preferably arc magnets or breadloaf magnets. The conductors of the magnetizing fixture are aligned with the stair step interfaces. A magnetic field induced in the permanent magnets is substantially reduced along the stair step interfaces.

Abstract: A permanent magnet synchronous motor system. The system uses a permanent magnet AC synchronous motor having an elongated housing, of the type used in progressive cavity pumping applications. Within the stator, a multi-section rotor is rotatably mounted. The rotor includes a plurality of rotor sections that are angularly offset from each other. The rotor sections are mounted on a drive shaft, and the sum of the offsets is generally comparable to the angular displacement undergone by the drive shaft under a normal operating load.

Abstract: A motor has an armature disposed on one of a rotor and a stator and a permanent magnet disposed on the other of the rotor and the stator. The permanent magnet has skewed magnetic poles being magnetized so that a boundary between each pair of skewed magnetic poles is generally S-shaped and opposed areas of pole surfaces of the permanent magnet and the armature gradually increase when the pole surface of the permanent magnet enters a magnetic field region of the pole surface of the armature or gradually decrease when the pole surface of the permanent magnet leaves a magnetic field region of the pole surface of the armature.

Abstract: An AC servo motor in which annular polar anisotropic magnets, formed by splitting an anisotropic magnet into two or more portions in an axial line direction, are used in a rotor. The magnetic poles of the split annular polar anisotropic magnets are disposed so as to be shifted by a predetermined angle &thgr;′ which is greater than a skew angle &thgr; determined based on the number of torque ripples per rotation of the rotor determined by the number of magnetic poles and the number of slots in a stator-side iron core. The predetermined angle &thgr;′ is the angle obtained after adding to the skew angle &thgr; a value which takes into consideration magnetic interference between the magnets. The invention provides an AC servomotor which can be controlled with high precision as a result of reducing cogging torque generated between the magnet and the stator-side iron core.

Abstract: A permanent magnet motor having a rotor 9 with a plurality of permanent magnets 8 disposed on the outer circumferential face at a predetermined interval in a peripheral direction, and a stator 6 with a plurality of magnetic pole pieces 3 arranged at a predetermined spacing in the peripheral direction, the magnetic pole pieces 3 being opposed to the permanent magnets 8, the stator 6 surrounding the rotor 9, wherein the auxiliary grooves 4 are provided on a face of each magnetic pole piece 3 of the stator 6 opposed to the permanent magnets 8 of the rotor 9, and a skew having an electric angle of 72° is provided relatively between the rotor 9 and the stator 6.