Abstract: A method for monitoring the speed of a synchronous motor, the synchronous motor having a permanent magnet rotor (3) and coils (1, 2), sinusoidal currents being applied to the coils (1, 2). Also a device for monitoring the speed of such a motor, wherein in at least one of the coils (1, 2) the power supply is disconnected and one or more voltage characteristics (U1, U2) are evaluated which are induced by the permanent magnet rotor (3) in one or more of the coils (1, 2) disconnected from the power supply, the minimum duration of the interruption of the power supply of the coils (1, 2) and the evaluation of the voltage characteristic (U1, U2) being equal to the temporal spacing between two consecutive zero crossings of the respectively induced voltage characteristics (U1, U2).

Abstract: A method to operate an electronically commutated DC motor driving a centrifugal pump and comprising a stator fitted with at least one winding and a rotor fitted with permanent magnets, said method including a monitored stepping operation within which one full revolution of the rotor is constituted by a sequence of distinct individual steps, the rotor being accelerated by applying a stator field and being decelerated to a stop before the stator field is commutated.

Abstract: There is provided a control method capable of stably rotating a synchronous motor synchronously with an output frequency even when a phase error between a real rotary axis and a control rotary axis is large. In a phase error operating unit, from the magnitude of the motor current, the magnitude of the motor voltage, the phase difference between the motor current and the motor voltage, and the motor constants, the phase difference between the motor current and the real rotary axis is determined as the first phase difference, and the phase difference between the motor current and the virtual rotary axis is determined as the second phase difference. The difference between the first and second phase differences is defined as the phase error, and the estimation position is so modified as to make the phase error zero.

Abstract: In a method of accurately estimating the rotor position of a synchronous motor having saliency from observable quantities, a control system for adjusting an output frequency of an inverter on the basis of a value of axis shift of the synchronous motor to operate the motor synchronously with the output frequency is provided with an induced voltage estimating/axis shift operating unit. Currents resulting from conversion of detection currents on a control axis, voltage commands to be inputted to an inverse converter and a speed command are inputted to the operating unit to estimate an induced voltage of the motor 2 and determine the axis shift from a phase of the estimated induced voltage. By using an electrical constant Lq of inductance, a voltage drop across the inductance is determined by the product of a motor speed command and magnitude of motor current. The voltage drop is a virtual quantity that does not depend on the motor rotor position.

Abstract: A method and apparatus for deriving characteristics of a utility signal for synchronizing the output of a motor drive with the utility for a transfer or capture operation. With the drive in idle, the voltage and phase angle of an input to the drive are detected by instrumentation of the drive. The voltage and phase angle of a signal from a utility are detected by instrumentation of the drive at the output of the drive. A phase angle difference and scaling factor are determined to correlate the input signal to the motor drive with the signal at the output of the motor drive. The phase angle difference and scaling factor are stored and subsequently used to derive the signal at the motor due to the utility at the time of the transfer or capture procedure.

Abstract: A pulse current having such a short duration as the rotor does not react is passed through field coils of respective phases of a brushless motor in first and second, mutually opposite, directions sequentially, voltages induced, by the pulse currents in two directions at each of the field coils of the non-conducting phase are combined, the polarity of a combined voltage is detected, and a field coil pair where a current is to be passed to start the motor is determined based on the result of detection for each of field coil of the non-conducting phase.

Abstract: A pulse current having such a short duration as the rotor does not react is passed through field coils of respective phases of a brushless motor in first and second, mutually opposite, directions sequentially, voltages induced, by the pulse currents in two directions at each of the field coils of the non-conducting phase are combined, the polarity of a combined voltage is detected, and a field coil pair where a current is to be passed to start the motor is determined based on the result of detection for each of field coil of the non-conducting phase.

Abstract: The present invention concerns a device (20) for controlling an electric motor (1) including a rotor (6) and at least three stator coils (2, 3, 4) connected between three connection terminals, means (5) for providing three control signals (Ua, Ub, Uc) to said connection terminals, and means (22) for dectecting said rotor angular postion. Said dectecting means include measuring means (24) designed to be connected to the motor, such that the means form with said coils at least two oscillating circuits supplying two respective signals (U1, U2) at two measurement frequencies respectively which are themselves periodic functions of said rotor angular position, and means (26) for calculating a single value corresponding to the two measurement frequencies, this value being the desired angular position.

Abstract: A method and device for controlling a synchronous permanent magnet motor with at least one phase, a coil and a rotor, wherein the method and device controls the powering of each motor phase, simultaneously measures the voltage of each motor phase, determines the rotor speed and the motor load from the measured voltage; determines a variable frequency from the speed and the load, samples at the variable frequency output signals from the voltage measurement of each phase; determines the rotor position from the sampled signals; and controls the powering of each motor phase as a function of the rotor position. The device is powered from an electric power source and comprises a power bridge powering the motor coil, a unit for controlling the powering of the coil, a circuit for measuring the voltage of each motor phase and means for sampling, at a variable frequency, signals from the measuring circuit.

Abstract: An object of the present invention is realizing a highly accurate synchronous control device which does not cause time lag by detecting the rotational frequency and phase simultaneously perpetually by same signal in the synchronous control of plural electric motors. The synchronous control device synchronizes accurately rotational frequency and rotation phase of an electric motor or a machine axis driven by the electric motor. A master section outputs phase signals or frequency signals based on rotational frequency reference.

Abstract: A power control system for a turbogenerator which provides electrical power to pump-jack oil well. When the induction motor of a pump-jack is powered by three-phase utility power, the speed of the shaft varies only slightly over the pumping cycle but the utility power requirements can vary by four times the average pumping power. This variation makes it impractical to power a pump-jack oil well with a stand-alone turbogenerator controlled by a conventional power control system. This control system comprises a turbogenerator inverter, a load inverter, and a central processing unit which controls the frequency and voltage/current of each inverter. Throughout the pumping cycle, the processing unit increases or decreases the frequency of the load inverter in order to axially accelerate and decelerate the masses of the down hole pump rods and oil, and to rotationally accelerate and decelerate the motor rotors and counter balance weights.

Abstract: In an a.c. motor control method and apparatus, operations are carried out at a current controller and a voltage setting using interrupt signals generated in synchronism with maximum and minimum values of a carrier wave at a control device for controlling an inverter for driving an alternating current motor. In operations at the voltage setting part carried out using one of the interrupt signals, a carrier wave is corrected in such a manner that phases of voltage command values gradually come into synchronism with a carrier wave. An integral multiple of the period of the carrier wave becomes the period of the a.c. voltage and current control operation timing is carried out in synchronism with the carrier wave.

Abstract: A device which detects the angle of rotation of a rotor with respect to a stator of a brushless multi-phase d.c. motor. The rotor comprises a permanent magnet and the stator comprises a plurality of electrical windings. Electric drive signals are applied to the windings in order to drive the rotor. The device includes a drive circuit for applying pulse-shaped electric test signals to the windings while the rotor does not rotate. A measurement circuit detects flyback pulses generated by the motor in response to the test signals. A processing unit processes the durations of the detected flyback pulses in combination in order to determine the angle of rotation. On the basis of the angle of rotation thus determined, the motor can be started such that the rotor is set into rotation in a predetermined direction of rotation.

Abstract: A method for restarting a three-phase synchronous permanent magnet motor in which the rotor is still rotating and in which the motor is connected to a drive unit having a DC-stage with voltage measuring means, a variable voltage and frequency output stage including power switching devices, and a means for determining the current in two of the output phases from the drive unit, wherein the motor with the output stage is momentarily short-circuited, the current magnitudes generated by the motor in the two output phases are measured during the short-circuiting moment, the phase angle generated by the motor during the short-circuiting moment is calculated, the rotor speed is determined, and the drive unit is synchronized with the rotor to enable restarting of the motor.

Abstract: In order to estimate a magnetic pole position of a permanent magnet type brushless motor, the following steps are conducted. A given &ggr; axis and a given &dgr; axis in an advanced from the &ggr; axis by an electrical angle of 90° are set. A closed-loop electric current control system in the &ggr; axis direction is formed while forming an open-loop electric current control system in the &dgr; axis direction. It is calculated an interference current generating in the &dgr; axis direction when a current command in the &ggr; axis direction is given as a stepwise alternating current command. The &ggr; axis is finely advanced by an angle of &Dgr;&thgr; when a sign of a product of an integral value of the interference current and a value of the current command in the &ggr; axis direction is positive. Alternatively, the &ggr; axis is finely delayed by an angle of &Dgr;&thgr; when the sign is negative.

Abstract: A commutation circuit for a sensorless three-phase BLDC motor enables soft switching in the commutation process without the need for a complex delay circuit and generates signals separate from the back EMF signals of the stator to start the rotation of the motor rotor. The commutation circuit includes a starting circuit adapted to generate a starting clock signal to forcibly start the motor without information associated with the position of the motor rotor and generates first, second and third reference clock signals that are used to drive the motor in constant velocity operation.

Abstract: A motor control system or electronic motor starter is optimized to replace electromechanical motor starters. Heat dissipation requirements are reduced by utilizing a by-pass contactor when the motor is in a run mode. The electronic motor starter derives power from an AC motor control signal conventionally utilized to power the coritactor coil associated with a conventional electromechanical starter.

Abstract: In an a.c. motor control method and apparatus, operations are carried out at a current controller and a voltage setting using interrupt signals generated in synchronism with maximum and minimum values of a carrier wave at a control device for controlling an inverter for driving an alternating current motor. In operations at the voltage setting part carried out using one of the interrupt signals, a carrier wave is corrected in such a manner that phases of voltage command values gradually come into synchronism with a carrier wave. An integral multiple of the period of the carrier wave becomes the period of the a.c. voltage and current control operation timing is carried out in synchronism with the carrier wave.

Abstract: A method and apparatus for cranking of an internal combustion engine in an AC electric traction motor propelled vehicle using inverters normally coupled to supply power to each of a plurality of AC motors. The inverters have DC input terminals connected between a relatively positive DC bus and a relatively negative DC bus and the DC buses are connected to DC output terminals of a rectifier. The rectifier has AC input terminals connected to stator terminals of a synchronous generator. The generator includes a field winding and a rotor connected in driving relationship to a crank shaft of the engine.

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: An electrical drive control system includes a controlled drive, an auxiliary generator, a control unit, and a power unit. The rotors of the controlled drive and of the auxiliary generator are connected so that rotation of controlled drive causes a corresponding rotation of the auxiliary generator. The control unit receives a first reference signal having a first frequency. The auxiliary generator receives a second reference signal having a second frequency. The control unit may generate the second reference signal. In response to the second reference signal, the auxiliary generator generates a primary information signal having a phase shift that is indicative of the rotational position of a rotor of the auxiliary generator and the controlled drive. The control unit receives a user selected position command indicative of a selected position of the rotor.

Abstract: A permanent magnet synchronous motor having multiple-phase armature windings and a rotor is subjected to sensor-less control. Phase voltages are generated in response to voltage command values. The generated phase voltages are applied to the armature windings. Phase currents through the armature windings are detected. The detected phase currents depend on the voltage command values. An angular position and an angular velocity of the rotor are calculated from the detected phase currents. The voltage command values are adjusted in response to the calculated angular position and the calculated angular velocity of the rotor to implement feedback control of the motor. An angular velocity of the rotor is estimated from a time-domain variation in the calculated angular position of the rotor. A determination is made as to whether or not the calculated angular velocity of the rotor and the estimated angular velocity of the rotor are substantially equal to each other.

Abstract: A sensor-less control apparatus is designed for a permanent magnet synchronous motor having multiple-phase armature windings and a rotor. The sensor-less control apparatus includes a first device for calculating a rotational angle and an angular velocity of the rotor from phase currents and phase voltages of the armature windings. A second device is operative for controlling energizations of the armature windings in response to the rotational angle and the angular velocity calculated by the first device. A third device is operative for correcting the rotational angle calculated by the first device into a correction-resultant rotational angle and informing the second device of the correction-resultant rotational angle, and for feeding back information of the correction-resultant rotational angle to the first device.

Abstract: The present invention employs digital circuitry to compensate for variations in DC link voltage transmitted to a switched reluctance machine. The digital voltage compensation system of the present invention periodically samples the DC link voltage and actual rotor speed, then supplies the samples in digital form to a microcontroller that derives a compensated speed signal to compensate for changes in DC link voltage.

Abstract: A method and circuit arrangement for controlling the position of a rotor of rotary motor or a linear motor, e.g. a stepper motor, synchronous motor or the like, has at least two stator windings and a rotor with salient poles, wherein an actual value of the rotor position, e.g. the angle of rotation or the displacement of the rotor, is determined and compared to a desired value of the rotor position, with the exciting current that flows through the stator windings to move the rotor being modified in dependence on a determination of the inductance of the stator winding. The inductance is determined by superimposing the exciting current with a periodic measuring current that has a higher frequency than the operating frequency of the motor so as to prevent the measuring current from influencing the excitation of the stator winding, and by measuring the reactive voltage drop caused by the measuring current across the stator winding.

Abstract: A control device for a salient pole type permanent magnet motor. A magnetic flux of a magnet is detected by an arithmetic operation or actual measurement, and a demagnetization rate is calculated in accordance with the thus detected magnetic flux. A target of controlling the phase is calculated with reference to a demagnetization rate obtained by the calculation. The phase of a motor current is controlled depending on the target of control obtained by the calculation. Thus, a torque is prevented from lowering due to demagnetization of the magnet.

Abstract: A control system for a permanent magnet synchronous motor includes a position estimator means having for cross correlating the back EMF of the unenergized winding with a reference waveform to determine the estimated position of the rotor for determining rotor angle position error; an error compensator, responsive to the rotor angle position error, for determining the angular speed of the field; an angle generator, responsive to the angular speed of the field, for generating the field angle position; and a waveform generator, responsive to the rotor angle position, for generating a periodic signal corresponding to each winding and designating a segment of that signal for driving that winding to adjust the field speed to the rotor 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: A synchronous generator usable in both a starting mode of operation and a generating mode of operation includes a permanent magnet generator having a permanent magnet and an armature winding rotatable with respect to the permanent magnet, an exciter portion having an exciter armature winding and an exciter field winding rotatable with respect to the exciter armature winding, and a main generator portion having a main generator armature winding and a main generator field winding rotatable with respect to the main generator armature winding. An inverter is coupled to supply power to the main generator portion armature winding via a DC link during the starting mode of operation, and a controller is coupled to the DC link for controlling the magnitude of the DC link current provided to the inverter during the starting mode of operation.

Abstract: A variable speed pumping up generator includes a first speed control unit for outputting a rotating speed command signal for controlling a pump turbine in accordance with a power output command and outputting an excitation control signal to an AC excitation unit of the generator, and a second speed control unit for controlling, in a generation mode, an amount of AC excitation from an AC excitation unit when a rotating speed of a rotary shaft departs from a lower limit setting or an upper limit setting. The setting is set in accordance with the rotating speed generated during a normal operation.

Abstract: A method and apparatus is provided for operating a permanently excited single-phase alternating current machine, otherwise known as a transverse flux machine, which allows optimal exploitation of the machine and economical design of the converter. A terminal voltage is applied to the machine, the shape of which is defined by the characteristics of the machine. The waveform of the terminal voltage converts from a sinusoid to a square wave, with a maximum voltage equal to the maximum available voltage, at defined switch-over times. Based on the switch over times, the resulting terminal voltage wave can be square, completely sinusoidal, or a combination of both.

Abstract: In a controlling apparatus of a motor, an address generating device generates digital address signals corresponding to a position of a rotor of the motor on the basis of the Z-phase, A-phase, and B-phase signals outputted from an encoder installed in the motor. A sine wave data for driving the motor is readout based on the digital address signal from a waveform memory device to drive the motor in accordance with the sine wave data by a PWM inverter. An abnormality detecting circuit detects agreement/disagreement of a timing level of an output signal of the waveform memory device which is binarized with using zero as a threshold and shifted a predetermined amount from a leading edge or trailing edge thereof and a level of the CS signal. A motor stopping device stops the motor in response to a disagreement detecting signal of the abnormality detecting circuit.

Abstract: A start assisting device for a high speed reluctance motor, capable of starting the motor at a specific start disabling position where a static torque with a very small angle is present due to a phase advance. When the motor can not be started at a specific position, clock signals are supplied as gate drive signals, in place of drive signals based on a motor position detection. After starting the motor, the drive signals based on the position detection is supplied as gate drive signals, so as to drive normally the motor. Otherwise, when the motor can not be started, the drive signals based on the position detection is supplied as gate drive signals for different phases, so as to start the motor. After starting the motor, the drive signals based on the position detection are supplied as gate drive signals for corresponding phases, so as to drive normally the motor.

Abstract: A method and apparatus for accurately controlling a hysteresis synchronous motor velocity eliminate low frequency hunting, which is characteristic of the motor. A nominal input phase current is modified by providing feedback information, thereby enabling a microprocessor control system to modify the phase of quadrature input current signal to the motor and thereby eliminating hunting of the motor. Accordingly, in a high resolution scanning application, speed variations which could cause disturbing artifacts to appear in an output image are eliminated.

Abstract: A current control apparatus is provided for PWM-control of motor current using a microprocessor. Since motor current enters a control processor as a discrete value, a delay in control always arises. In prior art, it is not possible to accurately predict the actual current value needed for PWM control; as a result, the gain of the current control loop cannot be made large enough. Accordingly, a change pattern of A/D-converted motor current is utilized to estimate what the motor current will be at the present point in time, and current control is carried out based on this motor current. As a result, the delay is made equivalently small and the gain of the current control loop can be freely set, thus improving the response of the current control loop.

Abstract: A control system for an AC excited synchronous machine for use in an electricity generator/motor system. The AC excited synchronous machine can be driven not only in a variable-speed operation based on 2-axis current control but also in a constant exciting frequency operation based on only direct-axis current component control. A phase signal is switched to drive stably the AC excited synchronoius machine in a self-excited operation or in a rotary phase modifying operation. Further, when it is desired to start pumping-up water, a synchronizing power is provided to keep constant the rotational speed of the machine at the time of establishing a desired water pressure. Because of the switching arrangement of the phase signal, the AC excited synchronous machine can be operated as an ordinary synchronous machine exhibiting ordinary synchronous characteristics, that is, self-excited operation characteristics, rotary phase modifying operation characteristics and pumping-up start characteristics.

Abstract: A multiphased permanent magnet generator (PMG) driven by a rotating shaft, generates a multiphase output which is integrated and applied as the input to a high resolution phase locked loop having a binary counter with an output phase locked to the PMG multiphase output and representing shaft position. As applied to a high performance synchronous drive in which the PMG is driven by the synchronous machine, the digital shaft position signal is used to generate a multiphase current reference signal which is tracked by stator currents generated for the synchronous machine by a power current source. The multiphase current reference signal can be generated by a selected set of multiphase digital sine waveforms stored in a ROM which is part of the phase locked loop or is a separate waveform synthesizer.

Abstract: A low noise, high bandwidth, sensorless vector control for a brushless DC motor includes a phase locked loop control having a digital counter and ROM look-up table which is responsive to a VCO to generate digital signals representing the sine and cosine of the instantaneous phase angle of the VCO. These signals are modulated by a current command and applied to a two-phase to three-phase converter. A flux sensor senses the air gap flux in the three motor coils and converts this signal to quadrature components which are compared with the output of the look-up table to derive a phase error signal that drives the VCO. Another feature of the invention is a timed self-starting network that cause the VCO frequency to ramp upwards then automatically switch to loop control without any abrupt change in the frequency of the VCO.

Abstract: A method and apparatus for preventing a current collapse in a phase not participating in the commutation, of a three-phase block current supplied synchronous machine, while the phase currents of the other two phases are being commutated. A control voltage controlling the synchronous machine is acted upon during the commutation of two phase currents by an additional control voltage such that the average of current drop in the down-commutating phase is equal to the average of the negative current rise in the up-commutating phase. Thus, a method and a circuit arrangement for carrying out this method are obtained with which the torque oscillations of a three-phase-feed drive can be reduced substantially.

Abstract: A gate-controlled electric drive comprises a synchronous motor (2) having m windings (2) and provided with a shaft position transducer whose output is connected to an address input of a permanent memory. The outputs for setting a pulse width code of said permanent memory are connected to inputs of pulse-width modulators, while outputs for setting a polarity code of said permanent memory are connected to inputs of a reverser. The outputs of the pulse-width modulators are connected to control inputs of corresponding control units, whereas inputs for setting polarity of the control units are connected to outputs of the reverser. The outputs of each control unit are connected to inputs of a respective switching unit based on bidirectional switches connected in a bridge circuit, a switching unit being connected to the respective winding of the synchronous motor.

Abstract: A torque angle control system for maintaining a predetermined torque angle in a synchronous motor having a speed command conversion circuit (10) for converting a speed command signal to a synchronous motor control signal, correcting the synchronous motor control signal and generating a fundamental signal related to the corrected synchronous motor control signal, position sensors (26) for sensing the rotational position of a rotor of the synchronous motor (20) and a comparator (30) for comparing the fundamental signal to a rotor position signal and outputting a correction signal to the speed command conversion circuit (10) for correcting the synchronous motor control signal to maintain a predetermined torque angle in the synchronous motor (20).

Abstract: A method for reducing a current break in a leg of a three-phase block current-fed synchronous machine that is not participating in a commutation while the currents in the other two legs are commutating. A triangular high frequency sampling voltage from a pulse frequency generator of a control unit for the converter that feeds the synchronous machine is always shorted at the beginning of the commutation for a predetermined synchronization time. The torque ripple of a three-phase feed drive is reduced using this method and the circuit arrangement for carrying out the method.

Abstract: The problem of excess size and weight resulting from the use of current sensors in a VSCF start system is solved by a motor control system which utilizes a current estimator to develop a current feedback value. The current estimator is coupled to a rotor position detector and an input power detector to develop a signal representing the estimated current drawn by the motor.

Abstract: A control system for a motor is disclosed in which the position of a magnetic pole of the rotor of the motor is detected to produce a position signal, a multi-phase rectangular wave signal is produced by an oscillation circuit, and the frequency of the position signal is multiplied to obtain a multiple frequency signal. A stepwise wave changing stepwisely, with the same frequency as the multiple frequency, is generated. A signal corresponding to the position signal or a phase difference signal representing a phase difference between the multi-phase rectangular wave signal and the position signal is selectively applied as a drive signal to the motor by a drive signal switching circuit. A first signal is produced before the stepwise wave reaches a predetermined level and a second signal is produced when the predetermined level is reached.

Abstract: A controlling device for a permanent magnet synchronous motor wherein a permanent magnet is used as a rotor and which includes three-phase armature windings comprises a detecting means for detecting a rotational position and a rotational angle of said rotor, a comparison means for comparing the rotational speed detected by said cetecting means with a predetermined reference speed and for developing a value of a difference between the rotational speed and the reference speed, a converting means for determining currents to be supplied individually to said armature windings in response to a vector value obtained from the rotational position detected by said detecting means and the value of the difference delivered from said comparison means, and a current controlling means for controlling current flows through said individual armature windings in response to values obtained by said converting means.

Abstract: In apparatus for controlling the rotational speed of a synchronous motor arranged to be driven by an inverter having switches for selectively energizing respective windings of the motor, a current detector is provided to an input of the inverter for detecting input current to the inverter to thereby interrupt energization of the switches by using an output of a first timer circuit when the current exceeds a predetermined value, and a second timer circuit is provided for interrupting energization of the switches on switching between respective phases of the motor. An interrupting time duration by the second timer circuit may be varied in accordance with the rotational speed of the motor and by the plugging state thereof.

Abstract: In speed control apparatus and method for a motor operable to drive a load whose magnitude varies over a predetermined period which use a unit for controlling voltage or current supplied to the motor such that the speed of the motor can coincide with a command speed, n pieces of data indicative of voltages or currents supplied to the motor and corresponding to n divisions of the predetermined period are independently stored in a read/write storage, at least one of the n pieces of data is corrected at the rate of each of the n divisions in accordance with a difference between the command speed and the speed of the motor, and the voltage or current supplied to the motor is controlled in accordance with at least the one of the n pieces of data, so that pulsation and noise occurring especially under low revolutions can be minimized.

Abstract: A system for controlling a polyphase electric motor, particularly at low speeds, using a load commutated inverter includes the generation of half sine wave signals within a range of desired frequencies which are subsequently converted to single phase alternating current power for application to selected windings of the motor. In a single channel polyphase embodiment, motor starting is achieved using zero current commutation and normal phase control. A two channel embodiment results in what amounts to two phase operation of the motor.

Abstract: A control circuit for operating a synchronous motor with a polyphase armature winding in a d-c voltage network comprises a switch device for successively connecting the winding phases with the network, a switch signal generator which produces switch signals for the switch device, a logical stage for logically loading the switch devices with said signals. The circuit also includes a voltage/frequency converter, a starting device and a re-starting device. The converter generates a pulse succession which is increased by the starting member from zero to a predetermined value to re-start the motor when its current exceeds a predetermined value.