Abstract: A method for setting parameters of an ECM motor, the method including: 1) energizing the motor and measuring the AC input voltage Vac; 2) allowing the motor to run according to recorded rotational direction data and rotational speed data when Vac>Vset1; 3) enabling the motor to enter a programming state of rotational direction data and rotational speed data when Vac<Vset2; 4) conducting the programming state including operating the motor in a rotational speed state, a rotational direction state, or a combined state thereof, with each state lasting for a time of T, respectively; and 5) determining that the programming state is proper when the user turns off the power; and storing the programming state in operation at the moment when the power is turned off as normal operating parameter of the motor.

Abstract: An inverter for a permanent magnet brushless dc machine, having a permanent magnet rotor and a set of stator windings, applies the full dc voltage provided to the inverter to each phase of the machine.

Abstract: A motor drive apparatus includes an AC/DC converter which converts AC power supplied from a power supply to DC power, a DC/AC converter which converts DC power to AC power and vice versa, a DC link unit which connects the DC side of the AC/DC converter to the DC side of the DC/AC converter and delivers the DC power from one to the other and vice versa, an energy storage unit which includes at least one capacitor storage unit and at least one flywheel storage unit each of which is connected to the DC link unit and stores or supplies the DC power, and an energy control unit which performs control so that the energy storage unit stores or supplies the DC power.

Abstract: A power supply circuit has an input terminal for electrically connecting to an active wire of an AC power supply, an earth terminal for electrically connecting to a neutral or ground wire of the AC power supply, and a voltage decreasing unit. The voltage decreasing unit has an adjustable capacitor unit with adjustable capacitance for decreasing an AC voltage applied to the input terminal and an output terminal for outputting the decreased AC voltage. An electric motor is combined with the power supply circuit to form a motor device.

Abstract: An anti-pinching device (18) for a pivotable actuating element (6) of a motor vehicle (2) is specified. Said device comprises a capacitive sensor (8) which is intended to contactlessly detect an obstacle in the path of the actuating element (6) and has an electrode (14) for generating an external electric field opposite a counterelectrode (16), wherein the electrode (14) extends in a radial direction (R) of the pivoting movement of the actuating element (6), and a control unit (10) which is set up to interpret a change in a measurement capacitance (CM), which is formed between the electrode (14) and the counterelectrode (16), as pinching when the changed measurement capacitance (CM) exceeds a triggering threshold (A) which is predefined on the basis of an opening angle (?) of the pivotable actuating element (6) and to track the triggering threshold (A).

Abstract: A motor, namely, a motor with minimum loss and improved efficiency is disclosed. More specifically, a motor having enhanced starting torque performance and increased normal operation efficiency is disclosed. In the motor in which a rotor is started using induction torque generated as power is supplied to a coil of a stator, the rotor includes a rotor core, conductive bars arranged, along a circumferential direction, in an outer rim region of the rotor core, to generate an induction current, flux barriers formed in the rotor core, to interrupt flow of a magnetic flux, for generation of reluctance torque, and magnets provided in the rotor core, to generate a magnetic flux, for generation of magnetic torque.

Abstract: The actuator (ACT) is intended to be linked to phase (AC-H) and neutral (AC-N) conductors. It comprises a motor (MOT) provided with windings (W1, W1), a capacitor (CM) disposed between two ends of the windings and the terminals of which form a first (P1) and a second (P2) phase terminal. It includes a switch (TR) controlled by an electronic unit (CPU) to link the common end of the windings to the neutral conductor, at least one pair of diodes (D1, D2; D3, D4), the diodes of one and the same pair being connected by an electrode of the same type to a resistive circuit (RA, RB, RC, DZ1, DZ2) connected to the neutral conductor, the other electrode of each diode being respectively linked to the first and second phase terminals and means (CS1, CS2) of detecting the state of conduction of the diodes.

Abstract: A low cost switching system for an electrical motor, which is speed sensitive, direction of rotation insensitive, load insensitive and voltage fluctuation insensitive. The switch contains a power supply, a control circuit, a zero cross detector circuit, a triggering circuit and an electronic switch to provide the switching action. A time delay hysteresis inducement circuit is provided in the switching system to energized and deenergized the capacitor at a predetermined synchronous speed of the motor. The switching system first checks the speed of the motor before reenergizing the start capacitor, which increases the life of the motor. The switching system operates in high temperature range and regardless the value of the capacitor used.

Abstract: A magnetizing motor having a permanent magnet body covering an outer circumferential surface of a rotor body, includes a speed detecting unit that detects a speed of the magnetizing motor; and a controlling unit that compares the speed detected by the speed detecting unit with a reference speed, and outputs a magnetizing control signal based on the result of the comparison.

Abstract: In an electric car control apparatus for driving an induction motor, detection accuracy of a DC voltage is improved. A DC power supply device is provided which has a maximum potential terminal A, an intermediate potential terminal B, a minimum potential terminal C, an upstream side capacitor 6 between the maximum potential terminal A and the intermediate potential terminal B, and a downstream side capacitor 7 between the intermediate potential terminal B and the minimum potential terminal C. Also, an overvoltage suppression part is provided which includes a resistor 8 and a thyristor 9 between the maximum potential terminal A and the minimum potential terminal C.

Abstract: A method and system for managing the voltage of a DC bus of a speed controller for an AC electric motor linked to a current distribution network. The method includes comparing a value of the voltage measured on the DC bus with a determined limit value, when the value of the voltage measured on the DC bus becomes greater than the limit value, forcing the slope of an internal ramp to a zero value so as to confer a constant frequency on the stator, and when the value of the voltage measured on the DC bus again becomes less than the limit value, progressively increasing the value of the slope of the internal ramp.

Abstract: A motor drive inverter control apparatus includes a rectifier circuit for rectifying an AC power supply, an inverter circuit driven by an output from the rectifier circuit, a motor driven by an output from the inverter circuit, a first capacitor coupled in parallel to the output of the rectifier circuit, and a second capacitor coupled in parallel to the first capacitor via a diode. The second capacitor has capacitance not less than three times that of the first capacitor. Although the second capacitor shows a ripple content not less than 90% during practical use, it well absorbs regenerative energy produced by the motor. As a result, elements of the apparatus can be prevented from degrading caused by an over-voltage, and the apparatus can be downsized and reduced its cost.

Abstract: A PWM motor drive circuit includes a drive IC member, a Hall IC member, a PWM converter circuit and a capacitor. The drive IC member electrically connects with the Hall IC member, the drive IC member further includes a pin electrically connected with the PWM converter circuit. The capacitor connects in parallel between the pin of the drive IC member and the PWM converter circuit, and further connects with a power source to supply a voltage to the pin of the drive IC member. When the motor is started, the capacitor can prevent occurring zero volts at the pin of the drive IC member so that the drive IC member cannot unexpectedly enter a high-speed mode.

Abstract: A motor control system for use in heating, ventilation and air conditioning applications including a blower and a motor coupled to drive the blower, an inverter coupled to provide energization to the motor, a relay capable of coupling the motor to the output of the inverter or to line power, and a controller providing signals to control the output of the inverter, where, upon startup and transfer of the motor from the line to the inverter, the output of the inverter is controlled by the inverter to provide for an enhanced startup or transfer.

Abstract: An inverter controller for driving a motor includes a rectifier having a reactor, an inverter, a capacitor, a generator which generates a voltage command value for each phase of the motor, a detector which detects a DC voltage between the DC buses of the inverter, a first corrector which calculates a voltage correction coefficient by comparing the DC voltage with a predetermined DC reference voltage, a second corrector which corrects the voltage command value by multiplying the voltage command value and the voltage correction coefficient, a selector which selects either two-phase modulation or three-phase modulation as a modulation type, a computer that computes a carrier frequency, and a pulse width modulation controller which controls a pulse width modulation so that a value of a voltage to be applied to the motor equals to the corrected voltage command value, by using the selected modulation type and the selected carrier frequency.

Abstract: A method and apparatus for monitoring voltage input to an appliance, such as a dryer, sensing when power input to the appliance is lost. In addition, a controller in the appliance pulses relay coils controlling motors and/or heating devices within the appliance to conserve energy on a backup capacitor that supplies the control circuit of the appliance in the event of power loss. Further, a voltage sense circuit outputting a square wave effects monitoring of the input voltage to the appliance by outputting the square wave signal whose cycle period is monitored to determine power outage. The controller stores current operation settings at the time of power outage in a memory device and ensures proper storage through the extra energy conserved from the capacitor by the pulsing of the relay coils.

Abstract: A permanent split capacitor motor operable in a full mode and in a modulated mode for improving efficiency. The motor includes a stator and a rotor in rotational relationship with the stator. The motor also includes a single set of windings wound on the stator. The windings are in a magnetically coupled relationship with each other such that one of the windings is a main motor winding while the other is an auxiliary motor winding. The windings define a plurality of A-ratios as a function of turns in the main motor winding compared to turns in the auxiliary motor winding. A switching circuit selectively energizes the first and second windings in a full mode configuration and in a modulated mode configuration based on motor load conditions. In the full mode configuration, the A-ratio of the windings is greater than in the modulated mode configuration.

Abstract: A capacitively powered motor having a power switching circuit adapted to be connected between a power source and its winding for selectively energizing the winding to generate a magnetic field which causes a rotating assembly to rotate. A position sensing circuit provides a position signal representative of the position of the rotating assembly and a commutating circuit controls the power switching circuit to commutate the power switching circuit at a commutating angle and at a substantially constant duty cycle to achieve a desired rotating speed of the rotating assembly. The commutating circuit varies the commutating angle in response to the position signal to maintain the substantially constant rotating speed of the rotating assembly. As result, the efficiency of the motor is varied to maintain the substantially constant rotating speed.

Abstract: A winding circuit for use with different input signals includes a first main winding, a second main winding, and an auxiliary branch having an auxiliary winding permanently and serially connected to a capacitor. The windings and auxiliary branch are alternatively configurable in one of a first configuration or a second configuration for use with respective first and second input voltages. When in the first configuration, the first main winding, the second main winding, and the auxiliary branch are connected in parallel. The input voltage signal then may be applied across the first main winding. When in the second configuration, the first and second main windings are serially connected, and the auxiliary branch is connected in parallel with one of the first and second main windings. The input voltage signal then may be applied across the first main winding and the second main winding.

Abstract: A retrofit power accessory for a turret mill provides a motor drive for changing machine tool speed, replacing a handwheel. A frame is attached to the mill by a pair of adjustable brackets which accommodate various models of mills. The frame carries a spider coupling which attaches to the rotatable machine shaft formerly holding the hand wheel. The spider coupling is driven by a gear motor on the frame through a timing belt and timing gears to positively drive the machine shaft. A manual switch controls the motor in either direction to effect the desired machine tool speed change. A rotary knob is also coupled to the spider coupling to allow manual intervention.

Abstract: An induction motor speed control apparatus and method wherein various capacitors are switched in series with the auxiliary winding of an induction motor and, during such switching, the power source is disconnected from the main and auxiliary windings and the in-use capacitors are momentarily connected to the main winding to form a closed-loop discharge path through the main and auxiliary windings.

Abstract: An electronic control for a motor which eliminates the motor centrifugal switch and more particularly a control for a domestic refuse compactor which permits the user to control the approximate full trash bag weight and obtain more compaction from a split phase induction drive motor. A ferrite core sensor on the main winding of the drive motor samples the lagging phase angle of the motor main winding current during a compaction stroke. A low force cycle is achieved by terminating the stroke as soon as phase samples fall below a threshold defined at the start of each cycle by a locked motor main winding phase sample acquired prior to starting the motor. A medium force cycle terminates the stroke when compaction forces exceed the main winding breakdown torque.

Abstract: A variable speed control system for a single phase AC induction motor wherein a controllable switch is in series with the main winding of the motor, while the auxiliary winding of the motor, which is in series with a capacitor, is continuously energized. The switch is opened whenever the current through the main winding passes through zero. While the switch is open, the back e.m.f. in the main winding is sensed to provide a measure of the speed of the motor. This is compared with a desired speed signal and the comparison is utilized to control closure of the switch. The speed of the motor then remains constant at the desired speed, even with a varying load.

Abstract: A polyphase alternating current motor has in addition to a main winding that can be connected to a voltage source, a auxiliary winding arranged in the stator, such that at least one condenser is connected to both windings per phase. A decrease in condenser size while at the same time improving the degree of effectiveness is possible by virtue of the fact that the main and auxiliary windings are arranged in such a way as to yield an increase and phase leading of the voltage adjacent to the condenser. The condensers are connected to the windings in such a way that only capacitative leakage current flows in the auxiliary winding and the geometrical total of active and leakage current flow in the main current.

Abstract: A control for an automatic washing machine with a reversing permanent split capacitor (PSC) drive motor. Separate ferrite core sensors surround each of two PSC motor windings. A sense winding is threaded through both sensors. A brief output voltage is generated whenever the alternating current in either PSC motor winding passes through a zero-crossing and when the sense winding is wound with proper mutual polarity, an output voltage is generated in response to zero-crossings of a brief, residual alternating current which flows in both PSC motor windings and the capacitor when the rotating PSC motor is cycled OFF. The circuitry, in combination with the sensors, samples the leading or lagging phase angle of the PSC motor auxiliary or main winding, respectively, at a sample rate of two-times the line frequency when the PSC motor is ON. The raw PSC motor phase data is used in microcomputer programs to compute motor start time or load torque dither.

Abstract: A motor drive system for driving a single-phase PSC motor, in which the two motor windings are conductively isolated from each other, from a two phase power source. In one embodiment, the PSC motor is supplied from a two phase inverter circuit. The PSC motor is also connectable through a four-pole double-throw switch to either a single phase source including a run capacitor or the two phase inverter circuit.

Abstract: A control for an automatic washing machine with a reversing permanent split capacitor (PSC) drive motor. Separate ferrite core sensors surround each of two PSC motor windings. A sense winding is threaded through both sensors. A brief output voltage is generated whenever the alternating current in either PSC motor winding passes through a zero-crossing and when the sense winding is wound with proper mutual polarity, an output voltage is generated in response to zero-crossings of a brief, residual alternating current which flows in both PSC motor windings and the capacitor when the rotating PSC motor is cycled OFF.

Abstract: To control the speed of an alternating-current drive capacitor motor of a centrifuge, the motor is connected to the bridge arm of a single-phase inverter. The bridge arm is connected at each of its ends to the midpoints of a series circuit of two capacitors and two field-effect transistors, these series circuits being connected in parallel with one another and connected to the output of a rectifier operated by the a.c. voltage supply. During operation, the capacitors are discharged by means of triggering the field-effect transistors alternately via the capacitor motor, the triggering being performed via a microprocessor serving as a pulse generator.

Abstract: An electronic circuit for starting a single phase induction motor operating from a source of alternating current, the motor having a cage type rotor, a coiled stator having at least a main winding and a starting winding, and a permanent capacitor connected in series with the starting winding. The permanent capacitor and the starting winding are connected in parallel to the alternating current source and the main winding in series. A TRIAC has a first terminal connected to one side of the alternating current source and a second terminal connected to the starting winding and to the permanent capacitor. A TRIAC trigger circuit is connected between the TRIAC second terminal and its GATE terminal and a bilateral swtich is connected to the TRIAC GATE terminal.

Abstract: An electronic control for a motor which eliminates the motor centrifugal switch and more particularly a control for a domestic refuse compactor which permits the user to control the approximate full trash bag weight and obtain more compaction from a split phase induction drive motor. A ferrite core sensor on the main winding of the drive motor samples the lagging phase angle of the motor main winding current during a compaction stroke. A low force cycle is achieved by terminating the stroke as soon as phase samples fall below a threshold defined at the start of each cycle by a locked motor main winding phase sample acquired prior to starting the motor. A medium force cycle terminates the stroke when compaction forces exceed the main winding breakdown torque.

Abstract: A capacitor-start capacitor-run single phase AC induction motor control starting circuit is provided which minimizes first cycle current spiking magnitude, and also minimizes cycle to cycle current spiking magnitude, without a choke or inductor in the loop containing the run capacitor, start capacitor and start switch. The first cycle current spiking problem is solved by controlling when the start switch may be turned on at initiation of the starting mode in relation to the AC cycle, to permit turn-on of the start switch only within a known or predictable range of voltage differential between the run and start capacitors. The cycle to cycle current spiking problem is solved by proper phasing of gate current, and supplying gate current to the start switch in phase with the voltage across the run capacitor and out of phase with the current through the series connected start switch and start capacitor.

Abstract: A motor control circuit for operating a permanent split capacitor motor from an ac source. The motor control circuit causes the motor to accelerate and decelerate according to a velocity profile. A driver circuit connects the motor to the ac source. The driver circuit receives a pulse signal at a predetermined time point after a zero crossing of the ac source and connects the ac line current to the motor at the predetermined time point, then the driver circuit disconnects the ac source from the motor at the next zero crossing of the ac source. A ramp wave signal is generated, each ramp thereof beginning at a zero crossing of the ac source and a dc voltage representative of the speed of the motor is also generated. A velocity profile having a predetermined period is provided on an output of a velocity profile generator. A first comparator circuit has a first input for receiving the dc voltage and a second input for receiving the velocity profile. An error signal is provided on an output thereof.

Abstract: In an induction motor rotor windings are connected together in a squirrel cage or a wound rotor .DELTA. configuration and stator windings are connected in series across a source. A capacitor is connected in parallel with one of the stator windings and this combination is connected in series with the other stator winding and is sized to form a quasi-double-resonant circuit. Both a single-phase and a polyphase motor can be configured as a quasi-double-resonant circuit with respect to each input power phase. A switching circuit employing compactors allows changing the rotation direction of the motor in a polyphase motor. A further polyphase motor is also described with primary stator windings connected to each power phase input and interleaved secondary stator winding, magnetically coupled to the primary stator windings but not directly connected to the power inputs. The secondary stator windings have capacitors coupled in parallel thereto to form parallel floating resonant circuits.

Abstract: A capacitor motor and method is disclosed which utilizes one or more tap points within the auxiliary winding of the motor which can be selectively connectd to a source of AC power via a selector switch for multi-speed operation of the motor.

Abstract: A speed-changing device for electric ceiling fans includes a run coil for electrical connection to a motor of a ceiling fan, and a starting and speed changing coil, together with a starting capacitor, parallel-connected to the coil. The starting and speed-changing coil includes a set of medium-speed taps and a set of low-speed taps, forming three speed-changing coils, in which speed-changing connections can be switched without producing any noise from the motor, by maintaining the same current direction after switching.

Abstract: A capacitive breaking circuit for a single phase induction motor using a double throw power switch which in the off position, connects a series string, consisting of a charging rectifier diode, a current limiting resistor, a centrifugal switch and a braking capacitor, to the two power input terminals of a small single phase induction motor. With this circuit, while the motor is running, when the power switch of the motor is turned ON, DC current also charges the braking capacitor. When the power switch of the motor is turned to OFF, the braking capacitor discharges through the motor winding via the power switch to produce the braking function.

Abstract: An induction motor includes a stator having at least one pair of stator windings and a rotor with rotor windings which are magnetically coupled to the stator windings via a circumferential air gap. The rotor windings are connected together in a squirrel cage or a wound rotor configuration. The stator windings are connected in series across the source. A capacitor is connected in parallel with one of the stator windings and this combination is connected in series with the other stator winding and is sized to form a quasi-double-resonant circuit, i.e., a quasi-parallel resonant circuit with the one winding and a quasi-series resonant circuit with the other winding. The stator windings are then grouped to form definite polar areas in the stator and a balanced rotating magnetic field is produced by all the windings throughout the entire load range when the motor is connected to a power source.

Abstract: An improved electric motor is operated from a single phase alternating current power source and employs a start winding and a run winding connected in series. A capacitor is connected in parallel with the start winding; and the inductance of the start winding and the capacitance of the capacitor are selected to form an LC resonant circuit at the operating frequency, thereby displacing the phase of the alternating current in the motor winding by 90.degree..

Abstract: An induction machine having a stator carrying phase coils divided into at least two independently fed sets of coils, with a rotor or armature carrying one or more loop members, each of which is a short-circuited, continuous isolated loop conductor member having elements thereof positioned and received within the slots of the armature in a generally serpentine configuration forming at least two open loop portions, each loop portion being in a spatially related position to a corresponding coil of the stator structure, with each conductor element within a slot phasing or linking the fluxes of one stator pole. The machine may be single phase or polyphase. At least one stator phase coil of a set includes a controllable device in circuit relation therewith to enable control of one stator coil relative to the other, either in current magnitude or in current phase shift, the controllable device being either a silicon controlled rectifier or a triac.

Abstract: This invention relates to motor speed control circuits employing capacitors. Two windings of a motor are connected in parallel to a neutral phase of an alternating current source. Each coil of the motor may be connected to the live phase of the source whereby the rotation direction of the motor may be altered. Three socket terminals are connected to each winding. A capacitor pack has three pins with two capacitors connected between a common pin and the two remaining pins. The pins of the capacitor pack can be inserted into the sockets in three different ways whereby either capacitor or the two capacitors in parallel can be connected across the windings to vary thereby the speed and performance characteristics of the motor.

Abstract: An apparatus for starting and running a plurality of three-phase motors from a single-phase power source is described. Two of the main coils of a three-phase motor are used to run the motor as a single-phase induction motor. The third coil of a three-phase motor is used as a starting coil and is selectively powered through a switch and a capacitor. The capacitor provides the necessary difference in the phase angle of the current in the starting coil and the main coils to provide starting torque for the operation of the motor.

Abstract: A capacitor motor and method is disclosed which utilizes one or more tap points within the auxiliary winding of the motor which can be selectively connected to a source of AC power via a selector switch for multi-speed operation of the motor.

Abstract: A motor starting control circuit is provided with an auxiliary switch (100), including a triac (102) and series resistor (114), connected across the start capacitor (5) for quickly discharging the start capacitor (5) upon disconnection of the start capacitor (5) from the AC source (4). This enables a lower rated start switch (6) by eliminating extra voltage thereacross caused by an otherwise charged start capacitor (5).

Abstract: Quieting circuits for synchronous electric motors bypass their phase shifting coils with a minor percentage of the total motor watts input.

Abstract: A circuit arrangement in which an a.c. load is connected in series with a capacitor unit suitable for a.c. connection. In such a circuit arrangement, the use of capacitors suitable for d.c. operation is made possible by the fact the capacitor unit is made up of two polar capacitors which are connected in series with the load in such a way that the capacitors are interconnected with matching poles, either directly or by way of the load with matching poles, as well as by the fact that a rectifier diode is connected to each capacitor, with the cathode of the rectifier diode being connected to the positive pole of the respective capacitor and the anode being connected to the negative pole of the respective capacitor.

Abstract: A circuit arrangement is disclosed in which a capacitive unit suitable for a.c. operation is connected in series with an a.c. load. An extension of the life of the capacitors can be achieved by having the capacitor unit consist of two capacitors connected in series either on the same side of the consumer or on opposite sides of the consumer, and that a separate rectifier diode is connected in parallel with each capacitor. Both rectifier diodes are connected with its forward direction opposite with relation to each other. This prevents reverse polarity voltage and charge, as well as reduces the duty cycle by fifty percent, thereby polarizing electrolytic capacitor life.

Abstract: A permanent split-phase capacitor induction motor having a capacitor (7) connected in series with an auxiliary winding (5) via an electronic switch (9) which is operated by a control circuit (11, 13) so as to obtain a higher starting torque than if the switch were permanently closed.The control circuit suitably comprises an integrating (21 to 31) responsive to the voltage appearing across the switch (9) and trigger circuit (19) which closes the switch when the output of the integrating circuit exceeds a threshold value, the integrating circuit resetting when the switch closes, and the switch reopening at the next current zero.

Abstract: Means for selectively reversing the direction of rotation of a permanent split capacitor (PSC) motor is disclosed. This means comprises an "add-on" or retrofittable kit electrically connected to the motor windings externally of the motor. In an overhead ceiling fan application, the kit comprises a reversing switch installable in the fan housing stationarily mounted around the fan motor. The reversing switch is a two position switch serially connected to the normal fan on/off and speed control switch which is typically located in a switch housing stationarily mounted below the fan blades such that when the reversing switch is one position, the fan will rotate in one direction (e.g., clockwise), and when the reversing switch is in its other position, the fan will rotate in the opposite direction. With the reversing switch in either position, speed control and energization/de-energization of the fan motor may be effected by actuation of the on/off and speed control switch in the normal manner.

Abstract: A three-phase delta-wound motor adapted for operation from a source of single-phase current, which motor includes first and second terminals adapted to be connected to the single-phase current source and substantially identical first, second, and third phase windings. A capacitor and the first and second phase windings are series-connected one with the other across the first and second terminals, the polarity of the first winding with respect to the second winding being opposite that of a normal delta-wound motor. The third phase winding is connected directly across the first and second terminals in parallel with the serially-connected capacitor and first and second phase windings.

Abstract: A permanent split capacitor single phase electric motor achieves balanced operation at more than one operating point by adjusting the voltage supplied to the main and auxiliary windings and adjusting the capacitance in the auxiliary winding circuit. An intermediate voltage tap on an autotransformer supplies voltage to the main winding for low speed operation while a capacitive voltage divider is used to adjust the voltage supplied to the auxiliary winding for low speed operation.