Abstract: An electric motor including a rotor configured to rotate about a rotational axis and a stator extending along the rotational axis. The stator may include a stator yoke, a first tooth, and a second tooth, each provided with a shaft extending away from the stator yolk towards the rotational axis to a base. Adjacent sides of the of the first tooth and the base of the second tooth may form a groove slot. A reinforcement element may be inserted into the groove slot.

Abstract: A wound rotor (1) has a structure defining a circumferential alternation of teeth and grooves. The teeth respectively receives longitudinal windings. The rotor (1) has longitudinal ends (17, 17?) and the windings defining, at the longitudinal ends of the rotor (1), protruding coil heads (40). A collar (10, 10?) for mechanically holding the windings is installed at one of the longitudinal ends (17, 17?) of the rotor (1) so as to define a central opening (101, 101?). A nozzle (21, 21?) projects a liquid coolant through the central opening (101, 101?) onto the coil head (40). The collar (10, 10?) has an escape duct (11, 11?) allowing escape of the liquid coolant projected onto the coil heads (40) to an outside of the collar (10, 10?). A longitudinal end of the collar (10, 10?) has a constant reduction in an outer diameter.

Abstract: A rotating electric machine includes a rotating shaft, a rotor fixed on the rotating shaft, a stator, a housing, a liquid coolant and a flow direction regulating member. The stator is arranged so that a radially inner peripheral surface of the stator radially faces a radially outer peripheral surface of the rotor through an annular gap formed therebetween. The housing covers both axial ends of the stator and rotatably supports the rotating shaft. The liquid coolant is provided in an internal space formed in the housing to flow into at least part of the annular gap formed between the radially inner peripheral surface of the stator and the radially outer peripheral surface of the rotor. The flow direction regulating member axially faces an axial end face of the rotor through an axial gap formed therebetween and regulates the flow direction of the coolant by means of the axial gap.

Abstract: There are described methods and systems for synchronizing at least two generators for an engine. A first generator is mechanically coupled to the engine. A power source is connected in parallel to the first generator and to a second generator, the second generator mechanically uncoupled from the engine, the power source connected across a same respective phase of a stator in the first generator and the second generator. Power from the power source is applied to the first generator and the second generator to align a respective rotor to the respective phase in each generator and cause the first generator and the second generator to be in-phase. The second generator is then mechanically coupled to the engine.

Abstract: An energy storage system including a solid steel flywheel rotor, journals, and separate stub shafts for connecting to the journals has improved material properties offers improved energy storage at reduced cost.

Abstract: A solid steel flywheel rotor having improved material properties offers improved energy storage at reduced cost. A process for manufacturing the rotor is also provided.

Abstract: A flywheel energy storage system incorporates various embodiments in design and processing to achieve a very high ratio of energy stored per unit cost. The system uses a high-strength steel rotor rotating in a vacuum envelope. The rotor has a geometry that ensures high yield strength throughout its cross-section using various low-cost quenched and tempered alloy steels. Low-cost is also achieved by forging the rotor in a single piece with integral shafts. A high energy density is achieved with adequate safety margins through a pre-conditioning treatment. The bearing and suspension system utilizes an electromagnet that off-loads the rotor allowing for the use of low-cost, conventional rolling contact bearings over an operating lifetime of several years.

Abstract: An electromechanical flywheel machine includes a flywheel mass and a motor-generator having a rotor rotatable about a stationery inner stator having stator windings.

Abstract: A connection device includes a body having a first and a second end, a first connector set at the first end, and a pin type connector set at the second end. The first connector set includes a first strip element and a second strip element, which form an electrical interface of the connection device. The pin type connector set includes a first element and a second element, and thus forms another electrical interface of the connection device, different from the electrical interface formed by the first connector set. The pin type connector may be projecting pins or hollows that receive pins. The first connector set is electrically connected to the pin type connector set. Thus, the connection device is adapted for electrically connecting a generator with an exciter having incompatible electrical interfaces.

Abstract: A hybrid excitation machine comprising a rotor having first and second rotor cores with an axial gap between; a stator placed radially outward of the rotor; and an exciting coil fixed to the stator placed in an air gap between the stator and rotor to protrude radially inward from the stator. In an axial direction, an axial end of a radially outer end of the first rotor core located on the second rotor core side and the second rotor core are positioned on opposite sides of an axial end of the exciting coil located on the first rotor core side, and an axial end of a radially outer end of the second rotor core located on the first rotor core side and the first rotor core are positioned on opposite sides of the axial end of the exciting coil located on the second rotor core side.

Abstract: A high-efficiency magnetic inductor rotary machine in which eddy current loss is reduced even if driven at super-high-speed rotation, and a fluid transfer apparatus that uses the same. In the magnetic inductor rotary machines, first and second stator cores are disposed coaxially such that circumferential positions of teeth are aligned, and first and second rotor cores are fixed coaxially to a rotating shaft such that salient poles are offset by a pitch of half a salient pole circumferentially, and are disposed on an inner peripheral side of the first and second stator cores. A salient pole width of the salient poles of the first and second rotor cores is configured so as to be greater than an opening width of slots of a stator.

Abstract: In a rotary electric motor a first stator core and a second stator core are disposed coaxially so as to be separated by a predetermined distance axially and such that circumferential positions of teeth are aligned, and a first rotor core and a second rotor core on which salient poles are disposed at a uniform angular pitch circumferentially are fixed coaxially to a rotating shaft so as to be positioned on inner peripheral sides of the first stator core and the second stator core, respectively, and so as to be offset circumferentially by a pitch of half a salient pole from each other. A first permanent magnet that is magnetically oriented such that a direction of magnetization is radially inward is disposed on an outer peripheral surface of a core back of the first stator core, and an outer peripheral surface of the first permanent magnet and the outer peripheral surface of the core back of the second stator core are linked by a frame that is made of a magnetic material.

Abstract: The invention relates to an electronically commutated electric machine (2) comprising: a rotor (21); an exciting winding (6) that is located at the rotor (21) in order to generate or alter a direct magnetic field in the rotor (21); a stator (22) comprising a three- or multi-phase stator winding (23) with phases that can be controlled via phase lines (8). The exciting winding (6) is connected to the stator winding (23).

Abstract: A rotary electric machine system includes: a stator that has multi-phase stator coils and that generates stator magnetomotive forces based on respective stator currents having different phases supplied to the multi-phase stator coils; a rotor on which rotor coils are wound such that magnetic poles are formed by rotor currents generated in response to the stator magnetomotive forces generated by the stator; a regulating unit that regulates a flow direction of each of the rotor currents to one direction to thereby regulate a polarity of each of the magnetic poles; and a control unit that controls currents supplied to the stator coils on the basis of a target torque. The control unit superimposes a pulse on the stator currents to adjust the ratio of each of the stator currents and each of the rotor currents so as to minimize a copper loss in the stator and the rotor.

Abstract: A permanent magnet-less, brushless synchronous system includes a stator that generates a magnetic rotating field when sourced by an alternating current. An uncluttered rotor disposed within the magnetic rotating field is spaced apart from the stator to form an air gap relative to an axis of rotation. A stationary excitation core spaced apart from the uncluttered rotor by an axial air gap and a radial air gap substantially encloses the stationary excitation core. Some permanent magnet-less, brushless synchronous systems include stator core gaps to reduce axial flux flow. Some permanent magnet-less, brushless synchronous systems include an uncluttered rotor coupled to outer laminations. The quadrature-axis inductance may be increased in some synchronous systems. Some synchronous systems convert energy such as mechanical energy into electrical energy (e.g., a generator); other synchronous systems may convert any form of energy into mechanical energy (e.g., a motor).

Abstract: A rotating electrical machine includes a stator and a rotor arranged to rotate inside the stator. The rotor includes a plurality of permanent magnets arranged to produce a radial magnetic flux in an airgap between the rotor and the stator. The machine also includes a stationary excitation coil. The rotor also includes a plurality of low reluctance elements. A current through the stationary excitation coil causes a magnetic flux to be established in a magnetic flux path which passes into the rotor through a first low reluctance element and out of the rotor through a second low reluctance element, which magnetic flux combines with the radial magnetic flux produced by the permanent magnets in the airgap. This arrangement can allow control of the field within a permanent magnet radial flux machine.

Abstract: In a separately excited electrical synchronous machine, and a method for operating a synchronous machine, coil windings, in particular in the form of excitation coils, are disposed on the rotor, the electrical supply of the coil windings being achieved with the aid of an inductive rotation transmitter, whose secondary winding is connected to the rotor and whose primary winding, which is inductively coupled to the secondary winding, is stationary, especially connected to the stator of the synchronous machine.

Abstract: Apparatus and methods provide for a high specific power electro-dynamo device that utilizes high-temperature superconductors, a dysprosium core, and superconducting coils to provide power. According to various embodiments, a rotor includes a number of rotor arms with a high-temperature superconductor attached to each arm. A stator includes a number of stator arms with stator coils wrapped around each arm. The stator coils may include superconducting wires for providing a charge to the high-temperature superconductors and non-superconducting wires for inducing a voltage from the trapped flux provided by the superconductors during operation in generator mode. The dysprosium core maximizes the magnetic flux saturated by the core while providing additional safety measures during operation. A backup power wheel or permanent magnets positioned in series with the high-temperature superconductors may provide emergency power at non-cryogenic temperatures.

Abstract: An electric motor (10) which includes an armature (11) with at least two armature phase pair windings (12) and salient pole rotor arrangement (15) having field windings (17) terminating in a selective electrical switch which determines the electrical continuity of said field windings (17). Also included is control means which is configured to regulate the magnetizing of the field winding (17) so that, at any given moment, one armature phase pair is usable for magnetizing the field winding whilst the other pair is responsible for torque production.

Abstract: The invention relates to an electrical machine (1, 110), which is in particular a synchronous machine, which has a primary part (3, 130) and a secondary part (5, 120), wherein the primary part (3, 130) has a) a first means (9) for producing a first magnetic field and b) a further means (17, 27, 29) for producing a further magnetic field, which in particular is an exciter field, and wherein the first means (9) has at least one winding, and the further means (17, 27, 29) is arranged in the region of an active air gap (21) of the electrical machine between the primary part and the secondary part and has magnetic poles, each having at least one permanent magnet (17).

Abstract: A self-magnetized motor includes a stator adapted to rotate by electromagnetic interaction with a rotator, a plurality of slot teeth formed on and surrounding a through-hole of the stator, and an excitation pole adjacent at least one slot tooth having fewer projections than remaining ones of the slot teeth. The projections are formed on ends of the slot teeth facing the through-hole of the stator. According to one non-limiting embodiment, the excitation pole may be formed between two slot teeth having fewer projections.

Abstract: The present invention relates to electrically magnetized synchronous machine comprising an electrically magnetized rotor, and electrically supplied sator windings, whereby it further comprises non-linear means, optionally controllable, such as rectifying means in a series with three sator phase windings, whereby a rotor field winding is arranged to be fed from said non-linear means.

Abstract: A single coil, direct current permanent magnet brushless motor including a stator including six alternately-wound coils connected into a single coil having first and second ends, the oppositely-wound coils forming stator poles, and six magnets of alternating polarity coupled to a rotor and rotatably journaled in the stator. A sensor, such as a dual output Hall sensor, is used for sensing rotation of the rotor. A drive circuit, such as an H-bridge circuit, is coupled to the first and second ends of the single coil to drive the motor. The H-bridge circuit includes two high-side switches for alternately receiving signals from the Hall sensor, and two low-side switches alternately receiving signals from the Hall sensor. A high-side switching signal can be controlled by an inverted low-side switching signal. A voltage boost circuit is also provided, having capacitors to provide a boosted voltage to alternately turn on the high-side switches of the H-bridge.

Abstract: A magnetic bearing control device that can operate a motor with low noise, has a simple system construction and is compact and inexpensive comprises: at least a pair of opposed electromagnets for supporting a suspended unit without contact; a motor M for rotating the suspended unit; and a controller for driving and controlling them. A DC/DC converter 13 supplies a driving power to an inverter 14 for driving the motor M. The inverter 14 for driving the motor M uses both PWM and PAM control schemes to drive and rotate the motor M.

Abstract: In a brushless direct-current drive with a synchronous motor (10), which has a stator (12) that supports a multi-phase stator winding (15) and a rotor (13) equipped with permanent magnet poles (20), and with a switch unit (11), which precedes the stator winding (15), for commutating the stator winding (15), in order to produce a fail-silent behavior, a field excitation winding (21) is disposed in the rotor (13), which winding can be supplied with current in the event of a malfunction so that it generates a magnetic flux oriented in the opposite direction from the magnetic flux of the permanent magnet poles (20).

Abstract: An alternating current generator, comprising: a disc shaped rotor and first and second ring shaped stationary cores, coaxially located with the rotor, the rotor further comprising a non-magnetic disc attached to a shaft, with a plurality of low permeability magnetic blocks fastened to the rim of the disc; the first stationary core being an electromagnet shaped so as to present magnetic poles to the rotor blocks; and, the second stationary core being an armature, further comprising: a low permeability magnetic core wound with a conductive coil, shaped so as to present poles which can be magnetically polarized to the rotor blocks.

Abstract: A superconducting rotating machine includes a direct current field excitation source and an alternating current armature winding mounted on a stationary support member, at least one of which includes a superconducting material, a core member formed of a magnetic permeable material and rotatable around the static support member, and a refrigerator unit which cryogenically cools at least one of the field excitation source and the armature winding. The superconducting rotating machine may have a construction for providing polyphase (e.g., three-phase) power.

Abstract: A controller for a switched reluctance machine utilizing a feedforward neural network in combination with either a fuzzy logic controller or a proportional-integral controller to provide output control signals (e.g., turn-ON angle, turn-OFF angle and peak current) for controlling the energization of a switched reluctance machine. In an alternate embodiment, a fuzzy logic controller is utilized by itself to control a switched reluctance machine.

Abstract: A brushless synchronous electrical machine includes a rotor rotating about a rotor axis, and a stator that includes at least one set of magnetically active stator cores projecting radially outward from the axis, and that also includes magnetically interactive crossbars on the radially outward ends of the stator cores. The rotor includes one or more magnetically active projections that sweep past the radially inward facing surfaces of the crossbars as the rotor rotates. Preferably, there are two sets of stator cores, displaced axially and staggered azimuthally with respect to each other. Stator windings are wound toroidally about the stator cores. The rotor is provided with a magnetic field, preferably by electrical current in one or more axial windings wound toroidally with respect to the rotor axis.

Abstract: A brushless permanent magnet machine that includes a combination of a fractional stator slot/rotor pole and a winding configuration to reduce cogging during operation of the machine. The stator has a series of teeth (preferably eighteen) which are surrounded by a series of coils. The coils are wound around the teeth and connected to a three-phase power supply in a manner that reduces cogging. The rotor has a series of slots (preferably sixteen). In the first embodiment, the coils are wound around every tooth, and the teeth are divided into sections of three, wherein each section of three teeth is connected to one phase of the power supply. In this embodiment, the fractional stator slot/rotor pole ratio is 18/16. In a second embodiment, the coils are wound around every other tooth, which provides for more space for winding the coils. In this embodiment, the fractional stator slot/rotor pole ratio is 9/16.

Abstract: A reluctance machine including a plurality of phase windings where each phase winding comprises a plurality of fractional-pitched coils. The reluctance machine may be coupled to a drive that can energize one, two or more of the phase windings to provide output torque that is derived from: (i) the self-inductances of the phase windings; (ii) a combination of the self-inductances of the phase windings and the mutual inductances between the phase windings; or (iii) the mutual inductances between the phase windings.

Abstract: A multiple phase heteropolar inductor electrical machine utilizing relatively movable stators and rotors wherein the rotors include electrical winding for producing electricity. The stators and rotors are spaced as to produce an electrical balancing among the machine phases. Preferably, a balance is achieved in the energy conversion process as measured over any given one-half electrical cycle within that phase. The machine substantially achieves equal and balanced peak torque per amp performance within a half cycle of operation of any given phase through the spacing between the stator and elements.

Abstract: A superconducting rotating machine includes a direct current field excitation source and an alternating current armature winding mounted on a stationary support member, at least one of which includes a superconducting material, a core member formed of a magnetic permeable material and rotatable around the static support member, and a refrigerator unit which cryogenically cools at least one of the field excitation source and the armature winding. The superconducting rotating machine may have a construction for providing polyphase (e.g., three-phase) power.

Abstract: A bearing system for positioning and supporting a rotor having a vertical shaft (20) coincident with a main rotation axis included in a flywheel (10) used for energy storage and high surge power in vehicular applications. The bearing system includes upper and lower radial force generators (110, 210) containing only electromagnets, and upper and lower axial force generators (120, 220) including an electromagnet and a permanent magnet. According to one aspect of the bearing system, each of the bearings includes control circuitry having simple and complex lead networks so as to permit the force generators to rapidly respond to vehicular transients while maintaining a preferred bearing stiffness. The bearing system also includes upper and lower touchdown ball bearings (130, 230) which are engaged only when the radial force generators are unable to maintain the rotor in a predetermined cylindrical volume within the flywheel (10).

Abstract: A reluctance machine system including a reluctance machine having a stator including at least one phase winding and a rotor defining rotor poles and inter-pole gaps, where permanent magnet inserts are positioned within the inter-pole gaps to interact with the currents in the phase windings to provide permanent magnet torque and to improve the machine's performance.

Abstract: A brushless synchronous rotary electrical machine comprises stationary stator and "inner" windings. Only the rotor moves. The inner windings are stationary helical windings, concentric with the rotor shaft and attached to the stator armature. Variation in time of the magnetic field associated with the rotor is provided by two magnetically interactive (ferromagnetic or ferrimagnetic) rotor projections that sweep past the sides of the inner windings as the shaft rotates, each projection including a certain number of lobes. The stator includes a magnetically active hub, within which the rotor rotates, from which project magnetically active stator cores. The stator windings are wound helically around the stator cores. Because all windings are stationary, brushes and rings are not needed. With three times as many stator cores as lobes in each projection, the machine functions as a three-phase generator.

Abstract: A reluctance machine system including a reluctance machine having a rotor and a stator including at least one phase winding and a full pitch auxiliary field winding where constant currents are established in the auxiliary field winding to assist in the establishment of a magnetic field in the machine so as to improve the machine's performance. A novel power converter uses residual energy remaining in the phase windings at the time the phase winding is de-energized (turned-off) to provide the constant energy for the auxiliary field winding.

Abstract: A reluctance machine including a plurality of phase windings where each phase winding comprises a plurality of fractional-pitched coils. The reluctance machine may be coupled to a drive that can energize one, two or more of the phase windings to provide output torque that is derived from: (i) the self-inductances of the phase windings; (ii) a combination of the self inductances of the phase windings and the mutual inductances between the phase windings; or (iii) the mutual inductances between the phase windings.

Abstract: A reluctance machine including a stator defining a plurality of stator poles and a plurality of stator slots, a rotor positioned to rotate with respect to the stator, and a plurality of phase windings, where each phase winding comprises a plurality of coils, where each coil is wound about more than one stator pole, where each coil comprises two coils sides, and where only one coil side is positioned in each stator slot, wherein the self-inductance of each phase winding varies as a function of the angular position of the rotor with respect to the stator. Also a reluctance machine similar to that described above where each of the phase windings is magnetic uni-polar.

Abstract: A brushless synchronous rotary electrical machine comprises stationary stator and "rotor" windings. Only the rotor moves. The rotor winding is a stationary helical winding, concentric with the rotor shaft and attached to the stator armature. Variation in time of the magnetic field associated with the rotor is provided by one or more magnetically interactive (ferromagnetic or ferrimagnetic) projections from the rotor that sweep past the sides of the rotor winding as the shaft rotates. Because all windings are stationary, brushes and rings are not needed. The geometries of the rotor, of the stator windings, and of the magnetically interactive part of the stator armature are arranged so that the entire length of the wire in the windings participates in the generation of AC current (in a generator) or torque (in a motor), and so that loss of power to eddy currents is minimized.

Abstract: A hybrid excitation type permanent magnet synchronous motor is provided with an armature and a rotor core arranged to be rotated relative to the armature. Permanent magnets are installed on the rotor core and generate magnetic flux which passes through the armature through a gap between the rotor and armature. Salient pole portions are integral with the rotor core and are not covered with the permanent magnets. The salient pole portions are arranged opposite to the armature through a gap such that the magnetic flux generated by the permanent magnets is effected by the magnetic flux passing through the salient pole portions. A direct current excitation coil generates the magnetic flux passing through the salient pole portions. Therefore, an operable speed area of the motor is increased without using demagnetization control and without degrading the efficiency.

Abstract: Difficulties in cooling the rotor (28) of a dynamoelectric machine carrying a rotating rectifier (54) are avoided by providing a coolant inlet 68 extending to the interior of a rectifier housing 50 through which the coolant may flow to emerge from a port 66 in the housing 50 and flow via an annulus 52 within the rotor shaft 30 to conduits 98 to cool the rotor windings 48. The coolant is returned to the interior of the rotor shaft 30 and ultimately to a coolant outlet 84.

Abstract: An AC machine system, in which the machine has an auxiliary rotating magnetic field, in addition to the main rotating field, with different speeds of rotation. The auxiliary field serves to induce AC voltages in the rotor windings, even when the machine is rotating at the synchronous speed of the main field. The induced AC is rectified, by having a rectifier circuit on the rotor, and provides DC excitation, to create fixed magnetic poles on the rotor. Thereby the machine functions at the synchronous speed of the main field, without the need for a DC exciting source, external to the rotor circuit. The presence of AC current components in the rotor coils, enable torque production at non-synchronous speeds also. The combination of main and auxiliary rotating fields can be implemented in several ways, such as a stator supply having more than one frequency components, or components of opposite sequence. It can also be done by appropriate design of the stator circuit.

Abstract: Cooling means are provided for directly cooling the bore bus bars which connect a direct current exciter such as a bore pack exciter to the field of an electric power generator. Two bore bus bars are separated by an insulating sheet have a circular cross section, and are surrounded by an insulating cylinder. The bore bus bars include an axially extending slot adjacent the insulation to form passageways through which cooling gas flows to directly cool the bus bars and pass through the generator to the cooling unit.

Abstract: Generator rotor for a turbo-generator in which the rotor winding is fed via two feeding conductors, which are each arranged in a bored channel in the rotor body. The two channels diverge in relation to one another and each channel is bored in part in an axial shaft portion of the rotor body and in part in the slotted rotor portion of the rotor body.

Abstract: When operating a synchronous machine as a synchronous generator, a suppression resistor is required across the main generator field. However when operating the synchronous machine as an induction motor, a current is induced in the main generator field which is typically greater than the current carrying capability of the suppression resistor.In order to overcome the foregoing problem, the present invention provides a centrifugally activated switch for mounting on a rotor and which provides an alternate current path for the induced current.

Abstract: A multi-phase electrical transformer includes a rotor-stator structure that provides varying-reluctance magnetic-field paths in which the magnetic fields pass through plural stator cores on which phased primary and secondary windings are mounted and through a rotor that includes two annular poles attached to cylindrical pole-connecting means. At least one of the annular poles includes at least one field concentrator member. An optional stationary field winding surrounds the pole-connecting means in the region between said pole-connecting means and the stator cores, and permits adjustment of power factor in primary or secondary windings. The structure permits separation of stator core and pre-formed windings for repair and permits the core and windings to operate at cooler temperatures without additional cooling apparatus. The device of this invention is capable of simultaneous operation as a transformer and a synchronous machine.

Abstract: An oil-cooled generator (10) is provided having a housing (20) with a gas-filled interior and rotor (46,56) therein. A stator (44,58) associated with the rotor (46,56) is secured to a surrounding sleeve (70',70) by an interference fit and pins (72',72). A bolt (84',84) is secured in an opening (82',82) in the housing (20) to fix the sleeve (70',70) thereto, the housing opening (82',82) being open only to the housing interior. The housing (20) is provided with grooves (76) therein and a ring (78) is secured to the inner diameter of the housing (20) to secure those grooves (76) to define oil passages (74) therein.

Abstract: The pole members of each phase of a synchro have quadrifilar windings wherein each conductor is wound over six poles associated with a given phase. A voltage signal from an alternating current source is impressed across one conductor from each phase connected in series. The remaining conductors are connected to produce resolver-based Rsin.theta. and Rcos.theta. signals directly from the synchro without conversion from the normal three 120.degree. out-of-phase signals.

Abstract: The present invention is a one-phase stepping motor having a predetermined direction of rotation. The motor comprises a rotor having 2p permanently magnetized poles on its outer surface. The rotor is surrounded by a coil, which when energized forms the main stator poles. Auxiliary pole arms extend into the space between the coil and the rotor.The rotor and coil are stored in a two-part housing which magnetically isolates the motor. The auxiliary pole arms extend inward from the top and bottom surfaces of the housing and are formed integrally therewith.The arrangement of the auxiliary pole arms serves to determine the direction of rotation of the rotor. Illustratively, the auxiliary pole arms are divided into groups. Within each group, the auxiliary pole arms are at a distance from the rotor that decreases gradually or in stages in the direction of rotation of the rotor.This one-phase stepping motor is especially suitable for driving counting mechanisms in electricity meters.