Abstract: A method and apparatus for starting a motor drive into a rotating motor, the method including determining an initial search frequency and search current wherein the current is less than a rated drive current, providing a d-axis flux generating current to the motor at the search frequency and at a magnitude equal to the search current, monitoring a q-axis flux error, decreasing the search frequency until the d-axis flux error is less than a threshold value, thereafter increasing the search current to the rated drive current and, after a flux-up period, providing both q-axis torque producing current and d-axis flux producing current to the motor.

Abstract: A circuit arrangement is provided for controlling an electric motor (2), in particular a three-phase, three-strand motor, which is coupled to an intermediate circuit voltage (4) via a DC/AC converter (3) having three DC/AC converter branches (7,8,9). A measuring signal (i.sub.b1,i.sub.b2,i.sub.b3) which is proportional to the branch current is derived from each of the DC/AC converter branches (7,8,9), and a control signal (I.sub.pn), which is substantially proportional to the total value of the strand currents (i.sub.1,i.sub.2,i.sub.3) of the motor, is derived from these measuring signals (i.sub.b1,i.sub.b2,i.sub.b3).

Abstract: An induction motor drive uses direct vector control for zero speed start up. According to the invention, a speed sensorless induction motor is controlled at all speeds, including zero or substantially zero speed, using direct vector control. In order to utilize direct vector control at all speeds, it is necessary to derive accurate stator flux vectors at all speeds. This is accomplished in the present invention by calculating two sets of stator flux vectors in diverse manners. A first set of flux vectors is derived from measured stator terminal voltage quantities, and a second set of flux vectors is derived from measured stator current quantities. The first set of flux vectors is valid at non-zero speed and the second set of flux vectors is valid at substantially zero speed. The direct vector control utilizes one of the two sets of flux vectors in accordance with predetermined criteria indicative of zero and non-zero speed conditions.

Abstract: An inverter is operated to eliminate hiss in the control of the speed of an induction motor using an inverter of variable frequency. The voltage is matched to the selected frequency to avoid such hiss and control of the voltage is effected by regulating spacing between the pulses outputted by the pilot unit to the gates of the MOSFETs or IGBTs forming the arms of the inverter.

Abstract: In a motor control system and method controlled by a d-axis current command value i.sub.ds and a q-axis current command value i.sub.qs, a d-axis voltage command value V.sub.d * and a q-axis voltage command value v.sub.q * are computed on the basis of d-axis current deviation .DELTA.i.sub.d of d-axis current value i.sub.d from the d-axis current command value i.sub.ds and q-axis current deviation .DELTA.i.sub.q of q-axis current value i.sub.q from the q-axis current command value i.sub.qs and on the basis of q-axis inductance value L.sub.q and d-axis inductance value L.sub.d wherein the inductance values L.sub.q and L.sub.d are tuned or adjusted so that the d-axis current deviation .DELTA.i.sub.d and q-axis current deviation .DELTA.i.sub.q approach zero.

Abstract: A d-phase current in the direction of a magnetic flux generated by a field system and a q-phase current in a direction perpendicular thereto are obtained from a driving current and a rotor phase of an AC servomotor by d-q conversion. DC-mode current control is carried out with this d-phase current adjusted to zero and using the q-phase current as a current command. In this DC-mode current control, the influence of magnetic saturation is restrained to lessen torque reduction by advancing the phase of the q-phase current command, which is effective component of the current command, in case of magnetic saturation.

Abstract: An excitation circuit is disclosed for balancing the phase voltages in a two phase motor. The excitation circuit includes a first and second switch and a port for receiving a signal to drive the switches. The excitation circuit also includes additional electrical circuitry which can be designed to adjust the speed and timing of the first and second switches and balance the phase voltages in the two phase motor.

Abstract: For achieving an air conditioner being applicable to various a-c source voltages in common and operative with high power factor by suppressing generation of high harmonics, an a-c source voltage from an a-c electric power source 1 is rectified in full-wave by a rectifier 2, and a d-c source voltage Ed of an inverter 13 is obtained by being charged in a condenser 5. Here, there are a-c source voltages of 100 V and 200 V, and a divided voltage Ed1 of the d-c voltage of the condenser 5 is selected when the a-c source voltage is 100 V, a divided voltage Ed2 (here, Ed1>Ed1) of the d-c voltage of the condenser 5 is selected when the a-c source voltage is 200 V, respectively by an exchange switch 18, and is used as a d-c voltage Ed' for controlling on and off of a switch element 6.

Abstract: A method for generating electrical frequencies of a alternating current motor is disclosed wherein a torque current command signal, a d-axis voltage command signal and a d-axis voltage feedback signal are combined to generate the stator electrical frequency in the synchronous reference frame. The method also provides an estimate of the rotor electrical frequency as well as of the motor speed. The frequency generator is preferably incorporated in a variable frequency motor controller for driving a motor at desired speeds independent of changing load conditions. The generator permits the controller to maintain field oriented control without the need for speed sensing and feedback.

Abstract: A circuit for operating an electric motor includes a feedback arrangement which generates a control variable signal that is supplied to a drive stage for the motor. The circuit also includes a monitoring arrangement to ascertain whether the motor is overloaded. The monitoring arrangement emits an overload signal if it detects an overload state, and the control variable signal is then reduced. In one embodiment, the monitoring arrangement detects an overload state by comparing a motor voltage signal to a motor voltage limit value which is a function of the motor current, and emits the overload signal if the motor voltage signal is smaller than the motor voltage limit value.

Abstract: The invention relates to a method and an apparatus for braking a synchronous motor (2) magnetized with permanent magnets. According to the invention, there is connected to the input connectors (38,40,42) of the synchronous motor a non-linear braking resistor (60) by means of which the stator windings of the synchronous motor (2) are closed.

Abstract: An electric current compensation circuit for use with a multiple-phase burshless motor to reduce ripples in the output torque is disclosed. It contains a plurality of electric current compensation loops each for a respective phase winding and each of the electric compensation loops contains: (a) a first input for receiving a line current from the driver; (b) a second input for receiving the compensation current from the motor sensor; (c) a forward rectifying circuit for forwardly rectifying the line current and the compensation current; (d) a reverse rectifying circuit for reversely rectifying the line current and the compensation current; and (e) a summation circuit for summing the forwardly rectified compensation current and the reversely rectified compensation current and outputting a synthetic current to a phase winding of the motor.

Abstract: A commutation control strategy for eliminating torque ripple and noise from a brushless motor which has a plurality of motor phases connected in a bridge, each phase having a top switching device provided between a phase winding and a positive voltage supply and a bottom switching device provided between the phase winding and a less positive voltage supply in which following commutations of the motor, when the current flowing in a first phase is decaying towards zero and the current in a second phase is rising from zero, the switching devices are operative between a state in which the current flowing in the first phase is caused to decay at a first rate, and another state in which the current flowing in the first phase is caused to decay at a second rate which is lower than the first rate so that the rate of decay of the current in the first phase substantially matches the rate of rise of the current in the second phase.

Abstract: The invention concerns an improved system for windshield wipers in vehicles. An induction motor is used, in which speed is accurately controlled by controlling frequency of power supplied to the motor. The induction motor may be of the consequent-pole type, which ordinarily does not produce sufficient torque. Addition of (a) auxiliary tooth slotting and (b) skew has raised the torque produced to acceptable levels.The invention includes a control system, which senses excess load on the motor, which occurs as the windshield dries, and reduces motor speed, subject to a minimum, in response.

Abstract: A speed sensorless hybrid vector control starts from zero speed by using indirect vector control with stator frequency equal to slip frequency. As soon as the rotor begins to rotate, the drive is converted to direct vector control for normal operation. The direct vector control uses several low pass filters. The first is a harmonic reducing filter for the sensed motor phase current and voltage signals. The others comprise integration apparatus used in the calculation of motor flux quantities from the motor phase current and voltage signals.

Abstract: A disk drive including firmware for overcoming stiction and breaking free the heads of a disk drive which may adhere to the disk surface when the disk is at rest. Upon start-up of the disk drive, if stiction at the head/disk interface occurs, the voltage to the spindle motor and/or actuator motor may be rapidly fluctuated so as to cause a pulsing of the spindle motor and/or actuator motor. Pulsing both the spindle motor and actuator motor creates forces in a plurality of radial directions to allow the head(s) to break free from the disk(s) in the direction of least resistance. Moreover, as the resonant frequency of the spindle motor varies depending on the number of heads that are stuck, the firmware pulses over a range of frequencies including the various resonant frequencies of the spindle motor corresponding to various numbers of heads stuck.

Abstract: An inverter control system for operating an induction motor calculates the primary magnetic flux vector and instantaneous torque value from the primary terminal voltage and primary current of the motor and produces a voltage vector to be delivered to the PWM inverter depending on the deviations of primary flux vector and instantaneous torque value from their command values and the phase angle of primary flux vector, with the switching of voltage vector being controlled so that the PWM inverter operates in a prescribed range of switching frequency irrespective of the period of calculation of the primary flux vector and instantaneous torque value. Setting the upper limit of switching frequency reduces the heat generation of the PWM inverter, allowing it to suffice with a smaller cooling device, and setting the lower limit of switching frequency reduces the magnetic noise and torque fluctuation of the motor.

Abstract: In a motor drive circuit, the collector-emitter paths of two npn-type transistors are connected in series between a power line and ground, and the junction between the two transistors is connected to a motor coil. A control circuit feeds a control current to the base of the transistor connected to the power line so that this transistor supplies a drive current to the motor coil. A current mirror circuit is provided which is constituted of two pnp-type transistors whose emitters are connected to the power line, and the base and collector of the input-side transistor is connected to the control circuit through a diode. The base of another pnp-type transistor is connected to the cathode of the diode, and the emitter of this transistor is connected to the collector of the output-side transistor of the current mirror circuit and to the base of the transistor connected to the power line.

Abstract: To improve operation when there are dynamic load requirements with a direct a.c. converter with a load connected to it in open circuit, the direct a.c. converter is controlled briefly such that the voltage vector resulting from the geometric sum of the phase voltages is increased while the phase relation remains the same.

Abstract: A driving apparatus of an induction motor applied for drive of a fan of an air conditioner has a voltage limiter unit for limiting an upper limit of an output voltage of an inverter circuit, a voltage slow-up unit for converting an output signal of an output voltage commanding unit into a signal which increases gradually when that output signal rises, a voltage slow-down unit for converting the output signal of the output voltage commanding unit into a signal which decreases gradually when that output signal falls, and a feed interruption processing unit for setting the output signal value of the output voltage commanding unit to 0 when interrupting feeding and delivering a feed interruption signal at the termination of the lapse of a predetermined time.

Abstract: A control system (100) for a five-phase brushless DC motor (102) including a stator having five windings and a rotor (116) mounted for rotation relative to the windings (114). The windings (114) are adapted to be electronically commutated in response to the rotary position of the rotor (116). The control system (100) includes a sensing circuit (106) to sense the rotary position of the rotor (116) using an optical or magnetic sensor or the back electromotive force voltages in the windings (114). Electronic switches (112) control the flow of current through the windings (114) in response to control signals generated by a control circuit (110) in response to the rotary position of the rotor (116). The control circuit (110) includes start-up logic to start the motor (102).

Abstract: An induction motor control system for electric vehicles having a DC power supply, an inverter, and an induction motor, includes a current control mechanism having a flux controller. The flux controller reduces the stator flux to improve the torque output of a motor at the limit of the voltage supply from the inverter. The reduction in flux is adjustable as the actual limit of voltage available to power the motor varies. A flux reference .lambda..sub.so generated according to efficiency control requirements can be adjusted by a flux weakening quantity generated by the controller in the constant power range of operation. The DC bus voltage, the rotor speed and stator flux reference values are input to the flux controller so that the motor can be operated to achieve improved torque output approaching the theoretical maximum torque output or to maximize efficiency as needed.

Abstract: A device for controlling a three-phase induction motor that is driven by an inverter connection. The inverter is furnished to be fed with full-wave rectified grid alternating voltage (U) and supply the motor's various phases (R, S, T) with the drive voltages phase-displaced in the normal way and which consist of mainly square, in relation to a virtual zero reference level, positive and negative half-periods which alternate at a fixed or adjustable drive frequency corresponding to the required speed. The full-wave rectified grid alternating voltage (U) supplied to the inverter is arranged to be supplied to respective motor phase (R, S, T) via an electronic switch connection (TR.sub.1H, TR.sub.1L ; TR.sub.2H, TR.sub.2L ; TR.sub.3H, TR.sub.3L) whose respective on and off periods are determined by the drive frequency which is generated by an oscillator device (15; 25). The last mentioned is arranged to be supplied with a voltage (U.sub.

Abstract: A method and an apparatus for direct torque control are specified for a three-phase machine fed via a harmonic filter, which method manages as far as possible without any major adaptation to already known DTC methods and DTC apparatuses. In addition, the oscillations caused by the filter are intended to be damped effectively. This is achieved in that a current flowing through the filter and/or a filter output voltage are/is measured, and the reference flux value and the reference torque value are corrected on the basis of the measured voltage and/or of the measured current. The correction comprises a transformation of the filter output voltage into a first component at right angles to a stator flux and into a second component parallel to the stator flux, as well as a reduction in the reference torque and flux values in proportion to the oscillating part of the filter output voltage.

Abstract: A control unit for a motor and a control method for it, which are adapted for conducting control at a high speed so that efficiency of the motor by inverter operation of an induction motor is maximum at all times. This unit comprises means (3) for detecting effective power delivered to a motor (14), calculation means (1, 2, 4, 5, 6, 7, 8 16, S.sub.1, S.sub.2, S.sub.3) for calculating, from the detected effective power and frequency (f) of an A.C. voltage delivered to motor (14), supply voltage (V.sub.1) to motor (14) where efficiency of motor (14) becomes maximum, and means (9, 10, 11, 12) for delivering the calculated supply voltage (V.sub.1) to motor (14).

Abstract: An electronic fast-starting system for a textile loom in which an asynchronous driving motor, whose phase windings are triangularly connected, is mechanically connected to the main crank shaft of the loom and is controlled by an inverter/controller receiving not only the set speed value but also the outlet signal of a speed detector situated on the main crank shaft.

Abstract: A method and apparatus for the control of an AC-machine is set forth with a special winding for the combined generation of a torque and of a transverse force in the machine. In this arrangement, the magnitude and direction of a transverse force acting on the rotor of an AC-machine is controlled via the current of a control winding of the machine. For this purpose, the magnitude and direction of a flux of the machine generated by a drive winding and also the torque-forming component of the drive current is detected. From these parameters, the desired value of the control current vector can be precisely calculated via a decoupling equation in a coordinate system which is rotating with the machine flux. Through vector rotation, through the flux angle and a constant angle, which takes into account of the position of the winding axes of the drive and control windings, the desired value of the control current vector can be transformed into the stator coordinate system of the control winding.

Abstract: A driver for an induction motor includes a voltage limiter which limits an upper limit value of an output voltage from an invertor circuit in accordance with an output frequency command, a lowest frequency limiter which limits a lower limit of an output frequency from the invertor circuit, a forward rotation limiter which outputs a first power supply interruption signal when the output frequency from the invertor circuit reaches the upper limit, a reverse rotation limiter which outputs a second power supply interruption signal when a reverse rotational speed of the motor reaches a reverse rotation limit level, and a low-speed overload detector which outputs a third power supply interruption signal when a state in which the second power supply interruption signal is not output continues in a low speed abnormality state.

Abstract: A control system for an induction motor of the present invention independently commands the torque current component and the exciting current component of a stator current group supplied to the stator of an induction motor so as to feed-back control the amplitude and phase of the stator current group. The torque current component is commanded to control the output torque of the induction motor in correspondence with the output of a steering force sensor for detecting the steering force. According to an electric power steering apparatus using an induction motor controlled by the control system, a permanent magnet is not used for the motor so additional equipment such as a clutch is not required. Consequently, the structure can be simplified and the size of the unit can be reduced. Further, manual steering operation can be performed in the case of failure.

Abstract: A motor torque control system has an inverter for converting a DC voltage from a battery into an AC voltage to energize an AC motor based on a command amplitude value. An input electric power calculating unit calculates an input electric power supplied from the battery based on a current and a voltage from the battery. A target electric power calculating unit calculates a target electric power to be supplied to the AC motor based on the rotational speed of the AC motor and a command torque value indicative of a torque to be produced by the AC motor. A PI control unit produces a control signal from the difference between the input electric power and the target electric power, and a PWM control unit controls the command amplitude value based on the control signal.

Abstract: A control system for an induction motor of the present invention independently commands the torque current component and the exciting current component of a stator current group supplied to the stator of an induction motor so as to feed-back control the amplitude and phase of the stator current group. The torque current component is commanded to control the output torque of the induction motor in correspondence with the output of a steering force sensor for detecting the steering force. According to an electric power steering apparatus using an induction motor controlled by the control system, a permanent magnet is not used for the motor so additional equipment such as a clutch is not required. Consequently, the structure can be simplified and the size of the unit can be reduced. Further, manual steering operation can be performed in the case of failure.

Abstract: A controller for a motor having at least one stator phase and a method for controlling the motor, the controller including a drive signal generator for producing an electrical drive signal in the stator phase, the drive signal resulting in a current flow in the stator phase such that the current flow varies in response to varying load conditions for the motor, a current sensor for monitoring the current flow in the stator phase, an error detector for producing an error signal related to changes in the current flow, and a manipulation circuit electrically connected to the error detector and to the drive signal generator for changing the electrical stimulus in response to the error detector.

Abstract: An inverter control apparatus for controlling a command frequency and a command voltage which are supplied to an inverter which then supplies AC power of a desired frequency, accordingly, to an induction motor. The inverter control apparatus receives a requested rotational speed of the motor and an actual rotational speed of the motor is obtained by detecting a frequency of a fluctuation component of a drive current supplied from the inverter to the induction motor. The difference between the requested rotational speed and the actual rotational speed represents a slip amount, which is added to the requested rotational speed to produce a command frequency. The command voltage is set to a voltage acquired when the monitored drive current is at a minimum value.

Abstract: An asynchronous motor is supplied with power from an AC line voltage via a variable speed drive including a rectifier bridge connected to the AC line voltage, a DC voltage intermediate circuit including a capacitor and an inverter including switches and connected to the phase windings of the motor. A system for controlling the power supply to the motor includes a device for controlled resumption of motor speed after supply of power to the motor is interrupted.

Abstract: A control unit for an induction motor which detects a primary current in an induction motor, obtains an error current which becomes zero when an actual value of the primary magnetic flux coincides with a set value provided as a product of I.sub.1d * and a primary self inductance L.sub.1, executes correction of the primary resistance, primary self-inductance, and leak factor according to the error current. Furthermore, the control unit has a correcting section control circuit in which a set error most influential for effecting coincidence between the primary magnetic flux in the induction motor with the primary magnetic flux is preferentially corrected.

Abstract: While an electric vehicle is traveling in a DC section, a ripple component detecting unit detects a ripple component appearing on a filter capacitor voltage and adds the ripple component onto an inverter frequency reference in such manner as to cancel an influence in a motor current caused by the ripple component. On the other hand, while in an AC section, a damping control component detecting unit detects a magnitude of fluctuation of a DC power supplied from a DC power line as a damping control component and adds the component, like the ripple component in the AC section, onto the inverter frequency reference in such manner as to cancel an influence in the motor current caused by the damping control component. Consequently, an output current from the inverter which is to be supplied to the induction drive motor becomes very steady of ripple-free and it improves comfort for passengers on the electric vehicle.

Abstract: An apparatus and method controls the speed of an AC induction motor by varying the frequency and current to the motor from an inverter power supply. A Counter EMF regulator receives a reference signal corresponding to the desired speed, and a signal proportional to CEMF for feedback. The output of the CEMF regulator is provided to the power supply to control the current to the motor. The CEMF feedback signal is also utilized to vary the output frequency of the power supply in accordance with the magnitude of the CEMF. This maintains the magnetizing component of stator winding current at a constant value for all operating frequencies of the motor. A signal corresponding to the load current component of the stator winding adds to the speed reference signal to the CEMF regulator to increase CEMF and frequency with increasing load, thereby to compensate for increased slip and maintain constant speed.

Abstract: An apparatus for driving an AC motor at variable speeds facilitates arbitrary setting or adjustment of equivalent primary resistance of an AC motor. In one embodiment of the present invention, a reference AC voltage generator outputs reference AC voltage values for each phase of the AC motor, and signals derived from the reference voltage values are in turn used by a power converter to supply the AC motor with variable voltage and frequency. In this embodiment, two or more phase currents are fed back to, and subtracted from, the reference voltage values via a regulator. In another embodiment, an angular-frequency/biaxial-reference-voltage value generator generates a reference primary angular frequency value and biaxial reference voltage values of the AC motor in a rotating orthogonal coordinate system. In this embodiment, two or more of the AC motor's phase currents are fed back to, and subtracted from, the biaxial reference voltage values via a vector transformer and a regulator.

Abstract: Apparatus for determining an estimate for the stator flux of an asynchronous machine when the supply frequency .omega..sub.s, stator inductance L.sub.s, at least one of stator resistance R.sub.s and an estimate R.sub.se therefor, and short-circuit inductance .sigma.L.sub.s are known, is carried out by structure for measuring the stator current 1.sub.s and stator voltage u.sub.s, calculating a difference voltage by subtracting at least one of the product of the stator resistance and the estimate thereof and the stator current from the stator voltage, integrating the difference voltage in relation to time to give a stator flux estimate .psi..sub.se, subtracting, prior to integrating a correction term based on the feedback stator flux estimate .psi..sub.se and being proportional to the product of the difference variable and the direction vector C given therefor, from the difference voltage, determining the difference variable from the equation:(.psi..sub.se -L.sub.s 1.sub.s).multidot.(.psi..sub.se -.sigma.L.sub.

Abstract: The problem of maintaining precision control of a synchronous motor is solved in a motor start control which utilizes an estimate of the amplitude of the fundamental wave component as a feedback value. The motor receives power from a main inverter and an excitation inverter. The inverters are controlled by a control unit which includes a pulse width modulation generator which is responsive to a voltage command and a commutation command to develop switching signals for controlling the switches in the main inverter. At speeds above a preselected minimum speed, the voltage command is developed in a closed loop manner responsive to a feedback signal representing an estimate of the fundamental output of the main inverter.

Abstract: A pump control system has a pump unit composed of a turbo pump, a motor for operating the turbo pump, and a frequency/voltage converter for generating a frequency and a voltage to energize the motor. The rotational speed of the turbo pump is varied in order to equalize the current of the motor to a constant current irrespective of the head of the pump. The pump can be operated to take fully advantage of the current capacity of the motor.

Abstract: Power is provided to the stator windings of an AC induction machine which includes a component at the fundamental drive frequency for the machine and a superimposed signal component which is at a substantially higher frequency than the drive power. The fundamental drive power is provided at a level which results in saturation in the stator which follows the magnetic flux vector. The stator response at the signal frequency is then detected to provide a correlation between the response at the signal frequency and the magnetic flux vector position. The detection of the response at the signal frequency is preferably carried out by a heterodyne detection process, by mixing signals at the signal frequency with the measured stator currents, and filtering the mixed signals to isolate the signal indicative of the flux vector position.

Abstract: The invention relates to a method of determining rotational speed, size and instantaneous direction of a residual flux of an inverter-supplied squirrel cage induction machine, to be used for starting the squirrel cage induction machine when there is a rotating residual flux (.PSI..sub.s) in the machine (1) and a total leakage inductance (.sigma.L.sub.s) of the machine is known. According to the invention measures are taken, comprising steps of short-circuiting stator windings; measuring a first stator current vector (i.sub.s1) and switching off the stator circuit at the end of a first time period (T.sub.1); short-circuiting the stator windings once more after a second time period (T.sub.2) from the end of the first time period (T.sub.1); measuring a second stator current vector (i.sub.s2) and switching off the stator circuit after a time identical with the first time period (T.sub.1) from the second short-circuiting; determining the frequency (.PSI..sub.s) of the residual flux (.omega..sub.

Abstract: Method and apparatus for robust integral-pulse control of servodrives of unknown dynamics. According to the current value of the controlled object position, a microprocessor controller presets the current values of pulse duration and pulse amplitude as functions of the position control or velocity control error. The current value of the pulse period is a function of the sum of (difference between) the current values of orthogonality and robustness parameters when the object moves with acceleration (when the object moves with deceleration). The orthogonality parameter is calculated in proportion to the current value of pulse duration under the condition of orthogonality of the adjacent pulses and the Indeterminacy Principle. The robustness parameter is a function of the current object acceleration/deceleration.

Abstract: Driving system and method for an electronically commutated multi-speed motor having a coiled stator and a rotor with at least one permanent magnet and having an electronic circuit that feeds voltage to the coils (1, 2, 3) of the stator according to a relative rotor position as sensed by a sensor mounted to the motor shaft, or by interpreting the voltages induced to the stator coils by the moving rotor. A voltage is supplied to an inverter circuit (10) whose output is applied to motor stator coils (1, 2, 3). The voltage applied to the inverter circuit is varied, making use of a speed switching circuit that can include a voltage multiplier or a voltage divider circuit and the variation of the inverter output voltage varies the motor speed.

Abstract: A control apparatus for compressor with induction motor includes a microcomputer which evaluates an optimum number of rotations at which an operation efficiency of a compressor becomes a maximum when a frequency of an alternating current electric power applied to an induction motor in accordance with a change of a load. An inverter circuit is controlled by the microcomputer, and therefore, a voltage outputted from the inverter circuit is adjusted such that the induction motor becomes the optimum number of rotations.

Abstract: An elevator car door is moved by a variable voltage, variable frequency linear induction motor which is driven open current loop to achieve a desired velocity profile indicated by an incremental linear encoder, with washed out proportional and integral gain. A magnetizing current insufficient to overcome the weight of the door is added in quadrature with the linear force current, and frequency is determined open loop in a predetermined fashion. Pulse width modulation voltage control signals are utilized to apply fixed voltages of correct polarity through a low pass three phase filter to the windings of the motor for correct intervals of time so as to synthesize desired sinusoidal winding currents. A boost of current is provided following each zero crossing of the sinusoidal winding currents to overcome lags therein. A ramp down of voltage avoids dropping the door at the end of door opening and door closing.

Abstract: A three-phase electronic inverter for an electric induction motor can operate the latter silently without the generation of magnetorestriction noise where the voltage of the rectifier outputted to the power transistor bridge is controlled by a TRIAC with regulation of the angle of conduction while the power transistor are pulsed in response to the output of a microprocessor through level adapters constituted by operational amplifiers.

Abstract: The present invention provides a current regulating method and associated apparatus for a voltage-injecting converter, wherein a flux-producing current component and a torque-producing current component of an actual current vector are regulated to corresponding components of a required current vector, whereby a precontrol variable is superimposed on each controller manipulated variable. According to the invention, the torque-producing controller manipulated variable acts on the flux-producing controller manipulated variable with delay as a function of a frequency variable, thereby providing a current regulating method which combines the advantages of two-component current regulation and active current regulation. This dual-action current regulation advantageously operates without requiring a structural switch between the two forms of current regulation.

Abstract: A method for starting an unexcited, multiple phase, alternating current induction motor rotating at an unknown speed is provided. The method includes generating an output signal with an AC drive at a predetermined frequency in order to energize the motor. The output signal has independently adjustable frequency and voltage components. A speed reference is provided which is functionally related to the frequency of the output signal. The voltage of the output signal is ramped at a predetermined rate and the frequency of the output signal is adjusted such that the voltage of the output signal equals the motor's set point and the speed reference is substantially equal to the speed of the motor. The motor then enters the normal operating mode.