Abstract: A rotary electric machine includes: a stator; and a rotor that face the stator and that rotates together with a rotation shaft, the rotor including: a rotor core including rotor salient poles and a slot formed between adjacent rotor salient poles, and a rotor coil wound around each of the rotor salient poles via an insulating member through the slot. Further, the rotor coil includes: a slot coil portion; and a coil end portion protruding from an end surface of the rotor core in an axial direction, the insulating member includes: a slot insulating portion; and an end insulating portion, and the slot insulating portion and the end insulating portion are integrated.

Abstract: A stator for a rotary electric machine includes a stator core and a stator winding. The stator core includes a core inner-peripheral portion including slots. The stator winding includes a phase winding including segment conductors. The phase winding includes parallel conductors connected in series. Each parallel conductor includes ones of the segment conductors connected in parallel. The segment conductors include weld end portions protruding from the slots, bent in circumferential directions of the stator core, and welded to one another to constitute conductor joint portions. The weld end portions include weld end portions which protrude from each of the slots and which include first and second weld end portions. The first and second weld end portions are bent in the circumferential directions. The second weld end portions are smaller in number than the first weld end portions.

Abstract: A system for cooling an electric machine having two components, one of the two components rotor and the other a stator, the two components enclosing a central axis of the electric machine coaxially, The rotor during operation of the electric machine rotates relative to the stator, wherein at least one axially oriented channel passes through at least one component. A fan is arranged at a first end of the at least one channel, wherein a turbine is arranged at a second end of the at least one channel. The fan is designed to enable air to flow, flowing from the first end through the at least one axially oriented channel to the second end.

Abstract: The stator is used for realization of drives and for generation electric energy in various fields of engineering. It provides reduction of basic and added electric losses in the stator winding at increased power. The stator includes a cylindrical stator pack (1) with a plurality of uniformly distributed slots (2) with an opening on the inner surface of the stator. In the slots (2) are laid double-layer winding composed of one or more than one double-arm sections (4) of wires having a rectangular cross-section, comprising an arm (5) adjacent to opening and an arm (6) to bottom of the slot (2), laid in two slots (2) distant from each other in step Y. The slot (2) is rectangular in one or two stages. The size (b1) in the radial direction of the cross-section of the wire, building at least one elementary double-arm section of the arm (5) near to an opening is at most equal to the size (b) in a radial direction of other wires in the slot (2).

Abstract: One embodiment is a unique Vernier machine comprising a rotor and a stator. The rotor comprises a back portion and a plurality of permanent magnets. The stator comprises a plurality of ferromagnetic arm structures, a plurality of ferromagnetic pole structures extending from each of the ferromagnetic arm structures in a direction toward the permanent magnets, and a plurality of conductive windings disposed about respective ones of the plurality of ferromagnetic arm structures. The ferromagnetic pole structures are structured to collect magnetic flux from the permanent magnets. The ferromagnetic pole structures of each of said ferromagnetic arm structures are spaced apart from one another according to a non-uniform pattern such that the ferromagnetic pole structures of a given ferromagnetic arm structure have substantially the same angular position relative to the permanent magnets radially opposite from the ferromagnetic pole structures of the given ferromagnetic arm structure.

Abstract: A singly-excited flux-switching electrical machine, that includes field coils and phase windings, is provided. The field coils and the phase windings are accommodated respectively in the unevenly shaped notches of a stator, such that the field coils and phase windings are radially offset.

Abstract: A vehicle system is provided and includes a 12 volt alternator and a 24 volt wound rotor configured for acceptance in the 12 volt alternator.

Abstract: A seat belt presenter for moving a tongue plate of a seat belt system to a desired position includes a transmission mechanism for moving the tongue plate and an electric motor for driving the transmission mechanism. The motor includes a stator and a rotor rotatably mounted to the stator. The rotor includes a motor shaft, a commutator fixed to the motor shaft, a rotor core fixed to the motor shaft and rotor windings wound about teeth of the rotor core and electrically connected to segments of the commutator, the rotor windings comprises a plurality of winding units. Each winding unit includes at least two coils, the coils of each winding unit being wound about the same teeth and electrically connected to a same pair of segments, in parallel.

Abstract: A vacuum actuator includes a vacuum partition wall, the interior of which can be evacuated to a vacuum, a rotor supported by the vacuum partition wall to be free to rotate, a permanent magnet provided on the outer peripheral surface of the rotor, a coil opposed to the permanent magnet, and a stator provided with the coil. The stator and the vacuum partition wall are formed integrally with each other.

Abstract: It is described a clamping system (30) of special conductors (S1, S2, S3) for a stator or rotor bar winding (U1, S1, S2, S3) for an electric machine, such as connection terminals (S1), jumpers (S2), neutrals or star points (S3), etc. The system (30) allows the special conductors (S1, S2, S3) to be clamped during a twisting step and/or a step of picking up such conductors from a twisting device (250). The system comprises a system axis (T-T), a plurality of grippers (10) aligned or able to be aligned along a circumference lying on a plane substantially perpendicular to the system axis (T-T) and actuation elements (50, 60, 70, 80, 90) of the grippers (10). Each gripper includes a pair of jaws (32, 33) mounted so as to be mobile in a plane transversal to said system axis (T-T).

Abstract: The present invention relates an electrical machine comprising a plurality of stator segments;each segment has a plurality of electrical phase windings embedded in stator slots in a phase sequence, wherein the phase of the first slot of a segment is different from the phase of the first slot of an adjacent segment.

Abstract: A stator includes: a stator core with N pieces of slots ranging along an axial direction, which are formed side-by-side along a circumferential direction; and a stator winding installed in the slots at the stator winding. The stator winding includes a plurality of winding groups, each made up with N pieces of lap-wound coils each formed by winding a conductor wire a plurality of times. The winding groups are disposed in a plurality of layers set side-by-side along a radial direction at the stator core. One coil side at each of the lap-wound coils is inserted in a specific slot on an inner side along the radial direction in a specific layer and another coil side of the lap-wound coil is inserted in another slot on an outer side along the radial direction in the specific layer.

Abstract: A small PMDC motor has a wound salient pole armature. The armature 22 has a winding guide 38 disposed within each winding tunnel 36 formed between adjacent salient poles of the armature. The winding guide 38 is arranged to separate the radially inner portion of the respective winding tunnel whereby windings 30 wound about the adjacent salient poles of the armature are restrained from entering into the opposite radially inner portion of the winding tunnel 36.

Abstract: Stator winding (10) for an electric machine, in particular for a generator of a motor vehicle, the stator winding (10) being embodied as an ordered stator winding (10), and the stator winding (10) being embodied in at least two axially spaced-apart levels (22, 24) in a winding head (13). The invention also relates to an electric machine and a method for manufacturing a stator winding (10) of an electric machine.

Abstract: The invention relates to a stator for an electric motor comprising several poles (P) that are directed inwards towards the motor axis (2) and that surround a rotor (1), each pole (P) being provided with one winding (L) and the coils of the windings (L) being wound around the poles (P) one after the other without interruption. The stator (20) contains at least three pole groups (n), having at least three poles (P) and each group having the same number of poles (P). The windings (L) run out from the end face at least at the respective beginning and end of a pole group and are contacted there in such a way that the windings (L) associated with each pole group contain their own connection pair (U-U?, V-V?, W-W?) and one connection (U?, V?, W?) of each of these connection pairs is connected to a star point (Y) on the end face of the stator (20).

Abstract: A stator includes a stator core and a stator coil formed of electric conductor segments. Each of the electric conductor segments has a pair of in-slot portions, a first end portion, and a pair of second end portions. The in-slot portions are respectively received in corresponding two slots of the stator core. The first end portion extends, on one axial side of the stator core, to connect the in-slot portions. The second end portions extend respectively from the in-slot portions on the other axial side of the stator core. Each of the second end portions includes an oblique part and a distal part. The oblique part extends obliquely with respect to an axial end face of the stator core. Corresponding pairs of the distal parts of the electric conductor segments are joined by welding. The oblique parts of the electric conductor segments have a higher hardness than the in-slot portions.

Abstract: A rotor for an electric machine having a number of poles includes a shaft that extends along a portion of an axis and defines an outer surface. A first core portion is formed as a single inseparable component and includes a first portion that extends from the outer surface to a first outside diameter to define a first thickness, and a second portion spaced axially from the first portion that includes a reduced back portion that extends from an inside diameter to the first outside diameter to define a second thickness that is less than the first thickness. A second core portion is connected to the first core portion and includes a second outside diameter that is substantially the same as the first outside diameter.

Abstract: A method of manufacturing a coil assembly unit comprises steps of coil forming, weaving, compressing steps. In the forming step, each coil wire is formed which provides linear portions and turn portions each connecting linear portions, during which bent portions are formed at both ends of each linear portion, the bent portions being bent so that mutually adjacent linear portions are deviated from each other. In the weaving step, the coil wires are mutually woven in turn, in which the turn portions intersect in turn. All the coil wires are subjected to the weaving step in turn to produce a woven coil assembly. In the compressing step, the woven coil assembly is compressed by compressing the woven coil so that each bent portion is deformed to be linear to allow the mutually adjacent linear portions to come closer to each other, thus producing the coil assembly unit.

Abstract: An electrical motor includes: a rotor; a stator including a stator core that is formed with a plurality of first slot units and a plurality of second slot units which are alternately disposed with the first slot units, each of the first slot units including at least two first slots, each of the second slot units including at least two second slots, the stator core being further formed with a plurality of first poles each disposed between the first slots of a respective one of the first slot units, and a plurality of second poles each disposed between the second slots of a respective one of the second slot units, the depth of each first slot being deeper than that of each second slot; a first winding that is wound on the first poles; and a second winding that is wound on the second poles.

Abstract: A reduced stress rotor tip fillet that may be utilized in generators and motors as well as other types of rotating equipment is disclosed herein. The rotor tip fillet may reduce stress via an inventive fillet configuration positioned between intersecting rotor faces.

Abstract: A manufacturing method of a winding assembly of a rotating electrical machine using a rotation block and a fixed block and a manufacturing apparatus used for the same. The rotation block includes a rotation surface rotatable around a rotation axis, and the fixed block includes a first surface and a second surface opposite to each other and a shaping surface. The shaping surface is formed between end parts of the first and the second surfaces, is made to have an almost semicircular shape with the rotation axis as the center, and extends along the rotation axis. Plural wire rods are simultaneously fed from the first surface of the fixed block to the rotation surface of the rotation block, and the wire rods positioned on the rotation surface are bent by rotation of the rotation block.

Abstract: A motor having a structure configured to reduce magnetic resistance between a rotor and a stator, a method for manufacturing the motor, and a washing machine using the motor are disclosed. The motor includes a rotor, and a stator co-operating with the rotor. The stator includes a main core and an auxiliary core. The main core includes a base and a plurality of teeth protruding from the base. The auxiliary core is structured to prevent the occurrence of magnetic resistance from being generated from spaces, defined between adjacent teeth, when the stator co-operates with the rotor.

Abstract: In a stator of an electric rotating machine such as a motor, there is provided with laminated 24 yoke pieces that form a yoke of circular shape when assembled and the yoke pieces are made rotatable relative to each other. Similarly laminated 24 teeth are each connected to each of the yoke pieces and a winding is wound on the teeth. In the stator, the teeth radially protrude inward in the yoke when the yoke pieces are assembled as the yoke such that some gap between adjacent teeth can be widened than others.

Abstract: To provide an aircraft propulsion system which can secure the optimum thrust and thrust vector for flight conditions, as well as the optimum sectional area for the engine, and which is highly compatible with the environment. An electrical generator is coupled to a turbofan engine, the electrical generator is driven by output power of the turbofan engine to output electric power, and an electromagnetic driving fan is driven by the electric power. On the other hand, after bringing each of coils in the electromagnetic driving fan to a superconductive state, liquid hydrogen is introduced to a heat exchanger, collects the energy of exhaust as heat, is then vaporized, and thereafter supplied to a combustor and to a fuel cell. Further, the electromagnetic driving fan is changed in its rotational phase by a rotating mechanism portion, is made movable in a width direction of a wing and a wing chord direction by a slide mechanism portion, and can be stored inside or outside the wing by a storage mechanism portion.

Abstract: In a rotary electrical machine, the stator is subject to eddy currents, causing losses. These losses are reduced by extending the path of the eddy currents whilst avoiding causing saturation. The invention therefore proposes to form recessed zones or slots (2) in the teeth (1) of the stator whose depth does not exceed one-half of the height of the tooth (1).

Abstract: A two-phase switched reluctance motor in an embodiment includes a plurality of salient rotor poles that each have asymmetric reluctances about a central radial axis of the respective rotor pole. Each of the rotor poles has the same width, and the rotor poles are operable to provide preferential torque generation in one direction of rotation for all rotor positions. Such preferential torque generation occurs under the influence of an electromagnetic flux, which is provided by a plurality of salient stator poles having substantially the same width as the rotor poles.

Abstract: A reluctance machine includes a stator having a stator core. The stator core includes a central bore and a plurality of stator poles extending inwardly from the stator core. Each of the stator poles includes a stator pole face. The reluctance machine further includes a rotor having a plurality of rotor poles. Each of the rotor poles includes a rotor pole face. Each of the rotor pole faces includes a first portion, a second portion that is radially inwardly stepped with respect to the first portion to create a non-uniform air gap between the rotor pole face and a corresponding stator pole face, and a protrusion located at an edge of the second portion of the rotor pole face.

Abstract: An electric motor for reducing torque ripple includes a rotor, a plurality of magnets positioned about the rotor, and a stator including a plurality of stator teeth configured to form at least two slot openings each having a slot opening width wo and a slot opening height ho. One or more of the stator teeth include a dummy channel having a channel height wn and a channel width wb. At least one of the slot opening width wo, the slot opening height ho, the channel height wn, and the channel width wb, are selected so as to minimize or reduce cogging torque.

Abstract: The invention includes an electric alternator/motor having a rotor, stator and at least one winding in the stator adapted to conduct a current, the machine also having and first and second magnetic circuits, one of which includes a saturable portion in which saturation may be controlled to permit control of the machine.

Abstract: A stepping motor includes: a magnet; a coil arranged concentrically with the magnet and to be opposed to a magnet, a predetermined clearance being provided between the magnet and the coil; and a magnetic member that surrounds the coil and includes a magnetic pole interposed between the magnet and the coil.

Abstract: An electrical machine including a rotor rotatable about an axis and a stator adapted to magnetically interact with the rotor. The stator including (t) teeth and one or more windings with compact coils disposed around the teeth. The one or more windings having (m) phases and (p) poles, where (t) is an integer and is greater than or equal to two, 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, and where (t/p=m/2) or (t/p=m/4).

Abstract: A stator of a wire connection structure is capable of producing an unlimited number of non-integer turns. This stator is made by turning back first to sixth conductors on the outside of an end face of a stator iron core, and by mounting them in slots at a predetermined slot pitch in each of U, V and W phases. The sixth conductor is divided into two 0.5 turns coils. Connecting in parallel 1.5 turns of each coil, in which the second conductor and a first of the coils are connected, and 1.5 turns of a coil in which the fourth conductor and a second of the coils are connected, forms a 1.5 turns coil. Connecting in series the 1.5 turns coil, and 3 turns of a coil formed by connecting in series the first conductor, the third conductor, and the fifth conductor forms a 4.5 turns coil.

Abstract: An iron core for an electric motor or an electric generator includes a core section, and at least two magnetic pole pieces formed at the core section. Each magnetic pole piece has at least two slits with difference depths extending from a surface thereof to be asymmetric with respect to a center line thereof so as to divide the magnetic pole surface.

Abstract: Rotary permanent magnet motors have salient stator poles with nonuniform pole thickness in the radial direction for compensating effects of cogging torque. Pole base portions terminate at pole shoes at the radial air gap. The pole shoes extend in the circumferential direction from the bulkier base portions. Variation of the thickness of the pole shoe changes the concentration of the effective flux at the point of coupling between the stator poles and the permanent magnet pole shoes. As there is no change in the active interfacing area of the pole shoes a uniform air gap is maintained. The torque signature for each stator pole/rotor permanent magnet interface can be selectively changed to smooth motor operation by configuring the stator pole shoe thickness to vary along its circumferential extent as appropriate. Pole shoes may have tapered leading or trailing edges with respect to a pole base to change the effective flux density in the air gap at a specific pitch of rotation.

Abstract: A method of manufacturing a piezoelectric thin film resonator forms, after forming a piezoelectric film on a substrate so as to cover a lower electrode formed on the substrate, a resist layer so as to cover the piezoelectric film, forms a mask composed of the resist layer on the piezoelectric film by forming, in the resist layer, an exposure hole for exposing a formation part of an upper electrode on the piezoelectric film, forms an electrode material layer for forming the upper electrode on the piezoelectric film exposed via the exposure hole and on the mask, and then forms the upper electrode by removing the electrode material layer on the mask by removing the mask.

Abstract: An invention is a new type of motor, a multi-circular flux motor. The invention has simple structure and comprises of a salient pole rotor and the silent pole stator. The stator pole is subdivided into plural teeth with the individual winding. A group of windings of each stator pole is connected in either series or parallel and is driven by one excitation phase. The movement of the invention uses multi-circular flux loops to produce reluctance torque to make the rotor moves. The multi-circular flux loops comprise of a series of flux loops that every flux loop is inversely rotation direction to each other adjacent. The invention can apply in a linear and rotating machine. By having plural winding poles and phases, the invention can be a poly-phase machine. The invention can be designed to be any number of poles and phases because all flux loops are separated. The invention is applied in both AC and DC machine and both linear and rotating machine.

Abstract: A vacuum cleaner assembly includes a motor having a rotor and a stator for providing motive power to the assembly. The rotor and stator each include armatures having tips. In one aspect, the widths of the rotor and stator tips are different. In another aspect, the rotor armatures have a non-constant width. Another aspect discloses the motor being a two-phase brushless motor having an even number (N) of stator armatures and N+2 rotor armatures. In another aspect, a rotor armature includes an aperture. In another aspect, each rotor armature includes a plurality of layers laminated together, with one layer being dimensionally different than the other layers. In another embodiment of the present invention, a control circuit energizes the windings of the stator so as to toggle the rotor in a first direction before alternately energizing the windings to drive the rotor in a second direction.

Abstract: An electric machine with a stator which comprises several grooves arranged adjacent to one another and forming winding chambers for accommodating at least one stator winding. Each stator winding is constructed of conductor bars with an essentially rectangular cross-section in the winding chambers and conductor portions forming winding overhangs. The conductor bars are electrically connected in an integral manner at their ends with the conductor portions in that each of the conductor portion comprises an essentially U-shaped end section with two opposite legs whose inner sides facing towards each other are joined with corresponding side faces of a end section of one of the conductor bars.

Abstract: A sequentially joined-segment coil for a rotary electric machine such an electric motor is provided. The coil has an end portion which is made up of heads of conductor segments and projects from an end of a core. The heads of conductor segments have turns or bulges. The bulges are lapped over one another in various forms or shifted in location in an axis direction of the core, thereby permitting the core to be decreased in diameter, which provides for decreases in size and weight of the rotary electrical machine.

Abstract: A reluctance-type motor include a stator having a plurality of salient stator-poles, a rotor having a plurality of salient rotor-poles, a multi-phase coils mounted in the stator, and a driver circuit for driving said multi-phase coil. The driver circuit starts to supply drive current to the multi-phase coils when the salient rotor-poles and the salient stator-poles come across each other. In other words, the drive current is supplied to the multi-phase coils when the inductance thereof is zero.

Abstract: A rotary electrical machine, comprising a stator (100) having at least one armature winding (140) mounted in slots which define stator poles, and a rotor (200) mounted for rotation inside the stator, the rotor having at its outer periphery magnetic poles comprising, firstly, North-South magnets (210N-210S), and secondly, magnetic reluctance pieces (215-215′), wherein the North-South magnets of two consecutive n, n+1 poles are grouped side by side, and in that the magnetic reluctance pieces of two consecutive n+1, n+2 poles are also side by side.

Abstract: A permanent magnet generator is so thin as to be incorporated in a 3.5″ diskette. The generator having so low cogging torque that can be rotated smoothly even by a low torque driving source as a 3.5″ FDD to generate stable output is disclosed. It has stator magnetic poles facing via a magnetic gap an outer circumferential surface of the stator permanent magnet having a plurality of magnetic poles on it. One to six of the stator magnetic poles are removed and instead of the removed magnetic poles provided is a soft magnetic piece to face the rotor magnetic poles. Grooves are preferably provided on the soft magnetic piece, facing the rotor magnetic poles. A notch is provided on the permanent magnet generator to avoid interference with an input/output terminal and/or a card contact terminal of the diskette for inserting a memory card.

Abstract: A sub-synchronous reluctance electrical machine having a stator provided with a core comprised of an assembly of magnetically uncoupled or weakly coupled sectors of ferromagnetic plates having longitudinal teeth arranged on the face thereof turned towards the rotor and provided with grooves to respectively house a winding. This winding is comprised of a plurality of coils surrounding a respective sector of the ferromagnetic material of stator in a properly distributed manner, so as to generate a magnetic field whenever this winding is energized. The sub-synchronous reluctance electrical machine possesses as an integral part thereof said rotor which in turn is provided with a core of magnetic plates having longitudinal teeth uniformly arranged along the face thereof turned towards the stator, said teeth being in a number different from the number of teeth of the stator.

Abstract: A brushless motor is composed of a stator for generating a rotating magnetic field by supplying three-phase alternating current consisting of U, V and W-phases thereto and a rotor having plural poles and rotatably disposed inside the stator. The rotor is rotated by the rotating magnetic field generated in the stator. The stator includes core teeth on which coils are wound. A tooth-group consisting of a center tooth and two side teeth is allocated to each phase, and excitation current in one phase is simultaneously supplied to three coils wound on the three teeth in the same tooth-group. The center teeth of each phase are positioned with equal intervals therebetween, while the side teeth are positioned so that they substantially coincide with the centers of the rotor poles when a center tooth in the same tooth-group coincides with the center of one of the rotor poles.

Abstract: A three-phase stepping motor comprising: a rotation shaft rotatably supported by a pair of bearings provided in predetermined places of a housing so as to be in opposition to each other; a permanent-magnet rotor formed in a cylindrical shape so as to have south (S) and north (N) poles magnetized alternately in the direction of rotation on an outer circumferential portion of the rotor, or an induced magnetization rotor having S and N poles disposed alternately in the direction of rotation which are formed in a manner so that permanent magnets with the same polarity are fitted or formed so as to be identical in polarity at their surfaces in grooves formed parallelly to each other at a regular pitch in a surface of a magnetic body formed to be cylindrical in parallel to the rotation shaft and the cylindrical magnetic body is subjected to induced magnetization to form the S and N poles alternately in the surface of the cylindrical magnetic body; and a stator disposed so as to be in opposition to a surface of one

Abstract: Salient poles made from soft magnetic steel plates have tip sections of approximately the same length as a rotor magnet. The salient poles are constructed with laminations in the circumferential direction, with axial dimensions adjusted with respect to the circumferential dimensions determined by the constraints of the winding to allow winding sections with a minimum required cross-sectional area so that magnetic saturation does not occur. These winding sections are inserted into coils wound with magnet wire, and press fitted into the stator which makes the magnetic circuit with the salient poles and forms the armature.

Abstract: A stator of motor into which two separate magnetic poles wound by conductive wires are assembled is applied. The stator has a minimized space between the magnetic poles, so that the magnetic leakage is reduced. The work efficiency of the motor is enhanced with lowered power consumption. The material consumption of coil is also reduced, and the assembly procedure is simplified to reduce the manufacturing cost.

Abstract: A variable reluctance electric motor includes a hollow cylindrical stator having a plurality of radially inwardly extending poles. Each of the stator poles is generally rectangular in cross sectional shape and is bifurcated into two stator teeth at its radially innermost end by a central, longitudinally extending slot. The outer circumferential edges of the stator pole teeth are beveled at their respective junctions with the sides of the stator pole. A stator pole gap width is defined between adjacent stator poles. A slot width is defined within each of the stator poles between the adjacent longitudinally extending edges of the slot. The ratio of the stator pole gap width to the stator pole slot width is in the range of from about 1.8 to about 2.3. A cylindrical rotor is co-axially supported within the stator for relative rotational movement. The rotor has a plurality of radially outwardly extending poles formed thereon. Each of the rotor poles is generally rectangular in cross sectional shape.

Abstract: A stator core for an alternator is constructed so as to satisfy the relationships h/hc<0.2, and 1.20<hc/bt<1.30 where h is the depth of recesses formed in the outer circumference of a base opposite teeth, hc is the width of the base, and bt is the width of the teeth.

Abstract: A rotor having permanent magnets for a brushless electromotor includes a yoke formed from a plurality of silicon steel sheets laminated together and provided along its outer periphery with even number of, at least four magnetic poles. The magnetic poles are alternately provided substantially at equal distances from a rotational axis with slots to receive the respective permanent magnets such that the sides of the permanent magnets facing a rotary shaft have the same polarity. As a result, a compact and efficient rotor is obtained, and damage to or flying off of the permanent magnets is prevented.