Abstract: An electronic control apparatus to operate an alternating current induction motor protecting same from power line blackouts, brownouts and providing self-adjusting, linearized, non-stepped reduced voltage output coinciding to work load to enhance efficiency, thereby reducing electrical energy used by the motor. This apparatus can be utilized in conjunction with a refrigerator, air conditioner or almost any home appliance to yield a substantial savings in electrical use.

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 method and apparatus to be used with an inverter based motor controller for determining current phase angles for the current on a single phase of a three phase AC motor from an inverter generated high frequency phase voltage sequence. The invention detects turn on delay periods and compares phase voltages during consecutive turn on delay periods to determine phase current zero crossing times which can be used along with phase voltage zero crossing times to derive current phase angle information.

Abstract: An inverter apparatus for driving a three-phase AC motor, having first and second arms each comprising plural parallel-connected transistors and plural parallel-connected diodes, is protected against overheating by detecting the composite current of the transistors and the composite current of the diodes in one of the first and second arms and determining the larger of the currents. The larger current, offering greater accuracy, is used to control the inverter. The apparatus is operative in either the regenerative or driving mode. Alternatively, a single detector can be used but the signal waves are clamped below a reference wave value.

Abstract: A plurality of step time tables consisting of a sequence of step times defining intervals between steps and thus a velocity profile to be executed by a stepper motor are stored in a first memory. A step table defining a plurality of identical sequences of excitation pattern for driving a stepper motor is stored in a second table. Identical DMA channels output the step times to a timer and the plurality of exitation patterns to a buffer. The timer measures the duration of the step times and when each step time expires generates a trigger signal which initiates the transfer of the next step time and next excitation pattern through the respective DMA channels. The buffer includes a control register which selects one excitation pattern from the plurality of excitation patterns output from the step table to be output for control of a selected one of a plurality of motors connected to the buffer.

Abstract: An apparatus for driving an electric motor according to a given control target, including a control circuit which generates a control command signal corresponding to the control target, a chopping signal generator which generates a chopping signal based on the control command signal generated by the control circuit, a full-wave rectifier which rectifies an alternating current supplied from an alternating-current power supply, and supplies a full-wave rectified current to the motor, and a chopper which is connected in series to a series circuit including the motor and the full-wave rectifier and which chops the full-wave rectified current supplied to the motor according to the chopping signal generated by the chopping signal generator.

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: The invention relates to a pulse-controlled converter, and a motor electric controller including such a converter. A first switch is controlled by pulses applied to its gate, these pulses being produced by a digital control unit linked to the gate of the first switch via a transformer. The transformer is linked to the digital control unit via a primary circuit and to the gate of the first switch via a secondary circuit. A second switch is directly controlled by the digital control unit. The secondary circuit includes a Zener diode and a resistor which are connected in series between a first terminal of a secondary winding of the transformer and the gate. The digital control unit generates a specific pulse synchronization sequence to control the converter so that problems of short-circuiting on the different bridge arms are avoided.

Abstract: Device for controlling electric motors of the asynchronous motor type operated by means of three-phase alternating current. For producing the operating current of the motor (5) a voltage-controlled oscillator (2) is foreseen and a generator (4, 6) controlled by the same and conditionally fed from a direct current source (1). The control device (3, 7, 8) is arranged to receive the pulse which arises upon operation of the motor (5) in its feed conductors (10-12) for alternating current and is thereby arranged to detect changes in the pulse shape of the operating voltage which occur due to electromotive forces induced from the motor windings when these are passed by the induced field of the rotor. These changes vary with the size of the slip. On the basis of the level of said deviations, a proportional voltage is induced which is transferred to the oscillator for its frequency control.

Abstract: An apparatus and method for controlling driving of a apparatus such as a motor. A signal representing the position and/or velocity of the motor is received by a drive control unit. A microprocessor in the drive control unit provides a division ratio signal and a rotation judging signal to a clock pulse divider and two-phase pulse generator, respectively, and also calculates the velocity of the apparatus in accordance with the condition data. The clock pulse divider divides a clock pulse signal in accordance with the division ratio signal and outputs a divided clock pulse signal. The two-phase pulse generator generates two-phase pulses having a 90-degree phase shift of a given polarity with respect to one another in accordance with the divided pulse signal, and reverses the polarity of the phase shift in accordance with the rotation judging signal. The microprocessor further outputs a control signal to control driving of the apparatus in accordance with the calculated velocity and the two-phase pulses.

Abstract: Digital device to regulate the speed of an electric motor having a commutating element mounted in series with the motor at the terminals of an A.C. distribution network. A duration of an on-state of the commutating element defines values corresponding to desired reference speeds. The digital device includes a tachometer sensor connected with the motor which emits pulses indicative of the speed of the motor, a microcontroller having an oscillator, a first counter whose count is tied to at least one period of the pulses to calculate an actual speed of the motor, a memory containing desired reference speed values, a comparator to compare the desired reference speed with the actual speed of the motor, and an interface to control the on-state of the commutating element.

Abstract: In an AC drive, a method for stator flux oriented control of a waveform generator providing switching signals to an inverter supplying pulse width modulated current to a three-phase, variable frequency induction motor is provided. The method includes generating a quadrature axis stator voltage signal, a direct axis stator voltage signal, and a stator frequency signal to which switching signals from the waveform generator to the inverter are responsive.

Abstract: An electric waveform generator for a brushless motor includes a triangular wave generator including a Voltage Controlled Oscillator (VCO), a shift register, an inverting circuit, an analog switch group, and a synthesizer. The shift register generates specified timing signals synchronized with the oscillating cycle of the triangular wave from the triangular wave generator. The inverting circuit inverts the triangular wave from the triangular wave generator. The analog switch group selects the triangular wave and the inverted triangular wave based on the timing signals from the shift register. The synthesizer outputs trapezoidal waves based on the operation of the analog switch.

Abstract: A brushless DC motor detects a positional relationship between the rotor and the stator windings in a short period of time when starting the motor and immediately switches the mode from a phase coincidence mode at the time of starting to a normal position detecting mode performed by counting output pulses in response to the rotational speed of the rotor. The motor detects a position of the rotor at an extremely high accuracy independently of the magnitude of the load even when the motor has already been subjected to the application of such a load at the time of starting. The motor is always driven at a high efficiency by applying a phase correction process so as to cause the phase of each of the voltages respectively induced in the stator windings to coincide with the corresponding one of the driving currents respectively outputted to the stator windings when the motor is being rotated normally.

Abstract: Power from a DC power source, such as a 12 volt RV or boat battery, is boosted and converted to provide an AC signal suitable for operating an induction motor such as a refrigerator compressor motor. The converter provides voltage pulses having a substantially constant width. The converted voltage signal frequency is initiated at a low frequency and ramps up to 60 Hz. A start winding control circuit is provided for activating the start winding for a limited initial period. A thermostat for controlling the activation of the compressor motor is connected in series with the motor load such that shutting off the compressor disconnects the motor from the circuit. Control circuitry monitors under voltage, over voltage, overcurrent, AC switching, and adequate delay before restart and controls the circuitry accordingly.

Abstract: A circuit arrangement for commutating a reluctance motor including a current generator which produces first and second cyclic sequences of current pulses. In response to the first cyclic sequence applied to the stator windings of the motor, a rotor travels a predetermined distance along a motion coordinate path. Application of the second sequence to the stator windings results in the rotor traveling at least twice the predetermined distance along the motion coordinate path. The second sequence, which is applied when rotor speed exceeds a predetermined level, is formed by omitting predetermined current pulses from the first cyclic sequence.

Abstract: A digital current regulator for controlling the operation of an inductance device such as an AC motor. A plurality of independently controllable insulated gate bipolar transistors are selectively enabled to vary the instantaneous phase and magnitude of current applied to an AC motor. To minimize induced back EMFs during current switching operations, a number of safeguards are utilized. Switching between adjacent states only is provided to minimize the magnitude of instantaneous current changes. A "ready blocking" function limits the maximum switching frequency to avoid significantly derating the switching device capabilities, while a "time out" feature assures system operation above at least a minimum switching frequency to further minimize the magnitude of instantaneous current changes. A time hysteresis function is provided to avoid switching device response to false feedback control signals.

Abstract: Inverter control method and apparatus which are immune to the influence of load disturbance and detection noise and permit stable minimization control of motor current, in order to attain high efficiency of an AC motor and of an inverter adapted to drive the same. A memory group is provided having a plurality of sets of memories for storage of data pieces representative of exciting current commands standing for manipulated variables and data pieces representative of motor currents standing for controlled variables. An upper limit value (IDUP) and a lower limit value (IDLW) defining a fluctuation region of the exciting current command are determined so that an exciting current command data piece corresponding to a motor current data piece which is the smallest of all the current data pieces in the memory group falls within the fluctuation region. The fluctuation region is determined so as to minimize the motor current, the exciting current command being fluctuated within the fluctuation region.

Abstract: An arrangement for supplying energy to a load having a low-pass frequency characteristic. A binary signal having a low-frequency component and a strong high-frequency component having a predetermined frequency is applied to a rejection filter adjusted to suppress the predetermined frequency. The rejection filter is of a type producing a ternary output signal.The load is supplied by means of a control circuit in such a way that, in response to the signal level at the output of the rejection filter, the load is supplied with a positive polarity, with a negative polarity, or the energy supply to the load is interrupted. In this manner a ternary energy supply is obtained having low power dissipation in the control circuit and in the load.

Abstract: The invention is carried out by providing an adjustable frequency power supply connected to an alternating current induction motor which is rotated at speeds in excess of 60 hertz. A plurality of sequential frequency ranges are selected which, together, comprise a total frequency range from a maximum frequency range in excess of 60 hertz to 60 hertz which is applied to the motor. For each frequency range, a maximum breakdown torque of the motor is determined. When it is desired to decrease the speed of the motor, it is decelerated sequentially through each frequency range at a different deceleration rate for each range such that the maximum breakdown torque of the motor within each frequency range is not exceeded. Each different deceleration rate for each frequency range is determined by selecting the minimum period of time, for each frequency range, during which the motor may be decelerated without exceeding the maximum breakdown torque of the motor within that frequency range.

Abstract: Method and apparatus for driving an alternating-current motor. A sinusoidal supply AC voltage is rectified into a pulsating, unsmoothed DC voltage, with sinusoidal half waves and from this DC voltage an alternating-current motor voltage is produced by means of controllable polarity reversal. The pulse width of this alternating-voltage of the motor can be modulated. The polarity reversal takes place in accordance with the supply frequency in such a way that the AC voltage of the motor is essentially composed of the sinusoidal half waves of the pulsating DC voltage. For this purpose, the motor speed can be altered by changing the AC voltage of the motor with a constant timing frequency, lying outside the range of audibility, into pulse-width modulatable voltage pulses.

Abstract: An improved induction motor control system utilizes an inverter supplying a variable frequency AC voltage to drive the induction motor, and volt/frequency (V/F) control section controlling the inverter to produce a suitable voltage and frequency in a predetermined relationship therebetween. A power factor detecting section is included to detect a power factor phase angle between the motor current and the inverter output voltage as indicative of an amount of load imposed on the motor. The detected power factor phase angle is compared with a predetermined phase angle which is a frequency dependent angle indicative of a standard load at a given frequency, in order to provide a control output in response to which the V/F control section alters the inverter output voltage out of the predetermined relationship with the frequency for improving motor efficiency. Thus, the detected load (i.e.

Abstract: A method for controlling a frequency converter having multi-phase output is disclosed and a frequency converter for applying the method. In order to achieve a good waveform the currents of the frequency converter are controlled via modulation in such manner that the current modulation periods of each phase are interlaced with the modulation periods of the other phases.

Abstract: Disclosed is an unusually light-weight, compact, self-contained, self-powered ball thrower adapted to be carried and transported in the trunk of a passenger vehicle. All rotary components are driven by miniature DC motors having permanent magnet stators to maximize lightness without sacrificing performance. The low power requirements of these motors is readily provided by an onboard AC to DC power converter or by a rechargeable storage battery. The housing is power-oscillated to vary lateral ball trajectory and the throwing wheels are tiltable to vary the vertical delivery trajectory. An ample capacity ball hopper collapses compactly when not in use and a special control circuit assures uniform ball velocity during closely spaced successive ball throwing cycles.

Abstract: A control apparatus for controlling the main circuit for driving an AC electric motor consisting of a diode converter and a pulse width modulation (PWM) power converting device, in which it is arranged that the DC current as the output of the diode converter is detected by a current detector, the AC component of this DC current is filtered through a high-pass filter, and a pulse-width-modulation control is exercised by a control circuit in response to the output of the high-pass filter so that the DC current as the output of the diode converter may be smoothed out in the main circuit by the PWM power converting device. By such arrangement, this control apparatus of an electric motor is made smaller in size and simplified in structure and enabled to control the power factor of the power source of the diode converter to close to 1.0.

Abstract: An induction motor system, including a housing, a stator supported by the housing and having a plurality of stator winding conductors positioned about an axis of rotation, and a rotor mounted in the housing for rotation about the axis of rotation, is provided with an integral electronic controller for dynamically and programmably controlling the currents supplied to individual conductors of the stator winding. The stator winding conductors are connected in common at one end and are individually connected to a switching circuit at the other end. The switching circuit supplies positive or negative current pulses through selected conductors. Pulse width modulated signals generated by the controller simulate sine wave energizing signals to provide various operating configurations. By programmed variation of the fundamental frequency, pole configuration, phasing and power level, the rotating speed, starting, acceleration, torque, reversing, dynamic braking and efficiency are dynamically controlled.

Abstract: An electric drive system uses a multiphase alternating current motor and inverter to convert power from a battery source to provide propulsion. The phase sets defined by the motor stator winding are excited by a corresponding plurality of inverters. Time harmonic currents in the windings are effectively suppressed by providing the drive motor in a configuration having high leakage inductance in the stator winding. The windings are arranged in sets of multiples of three-phase windings. In the illustrated embodiment, the inverters are arranged to define three-phase inverters for exciting m sets, where m.gtoreq.2, of three-phase windings of the motor stator. The number of multiphase winding sets is determined in a manner that eliminates the need for paralleling of inverter switching devices.

Abstract: An arrangement of interconnected timers is provided for operation with a microprocessor programmed to determine time delay counts that are fed out to these timers such that the timers can take care of the actual task of firing GTO inverter switches or not firing GTO inverter switches coupled with an AC traction motor for a vehicle. It is necessary to have correct transitions between the minus GTO switch and the plus GTO switch being ON for providing the desired motor voltage conditions with minimum electromagnetic interference in relation to the power supply. In addition the use of timer queues in complicated synthesis modes like the PWM and the quasi six-step operates to give the microprocessor adequate operating time for reasonable control signal time duration calculations. The timers are synchronized in hardware by a single crystal frequency, and they are synchronized in software such that the three phase independent waveforms stay 120.degree. apart.

Abstract: In a static DC/AC converter sequentially fired in relation to the frequency of the AC power supply, gating is provided by down counters which are instantly advanced, or delayed, in accordance with a change in the reference frequency, thereby to provide instantaneous firing angle adjustment.

Abstract: The drive circuit has a pair of windings associated with each phase of the motor, with the windings of each pair being connected in antiphase. The circuit comprises a d.c. supply, respective semiconductor switches in series with each motor winding for supplying current from the supply to the associated winding in only one direction, and frequency control circuitry for switching the switches on and off so as to cause the windings of each winding pair to conduct current alternately and in opposite directions at a frequency which may be varied so as to vary the speed of the motor. In this arrangement there is no possibility of a short circuit path occurring which does not incorporate one of the motor windings, so that the rate of rise of fault current is finite and over-current detection circuitry can be used to turn off the switches or operate a crowbar.

Abstract: In a pulse-width modulated unrestricted frequency changer (UFC) the harmonic contents of the input current are minimized by splitting the active time intervals within the fundamental time frame into at least two pulses which are located within such time frame and controlled in width as if individual PWM single-pulse UFC's were controlled having a phase shift between each other so as to eliminate or reduce undesired frequency components. Such elimination or minimization of selected frequency components is used to reduce the size of the lowpass filter at the input of the UFC, namely by allowing a higher cut-off resonance limit.

Abstract: In a static frequency changer controlled by adjusting the time of conduction of the bilateral switching units forming static converters, the time of conduction is split into n time intervals of respective subdurations adding up to be equivalent to the effective time of conduction of the controlled switching unit, and such subdurations are spread and distributed throughout the time period of control of the switching unit both within the original switching pattern of each converter and between the effective times of conduction of the respective converters, thereby to minimize harmonic distortion of the input supply current of the frequency changer.

Abstract: An apparatus for controlling an A-C powered elevator in which A-C electric power is converted into D-C electric power through a rectifier, the D-C electric power thus converted is converted into a A-C electric power of a variable frequency via an inverter, an A-C electric motor is driven by the thus converted A-C electric power, the A-C motor being controlled by a controller which is connected to a D-C control source, a cage is driven by the thus controlled electric motor, said motor producing regenerated electric power depending upon the operation condition of said cage, wherein provision is made of a regenerated electric power controlling device which is connected between the D-C side of the inverter and the controller in order to supply the regenerated electric power to the controller. When the voltage on the D-C side of the inverter becomes greater than a predetermined reference value, a switching element is rendered conductive, and the regenerated electric power is supplied to the controller.

Abstract: A motor operated valve, typically a butterfly valve driven by a synchronous electric motor (16), is provided with a torque sensing arrangement wherein an cyclic electrical signal representative of the rotational speed of the motor is produced by magnets (22) on disc driven by the motor and Hall effect switches (23,24). The frequency of this signal is compared in a circuit (43) with the frequency of current supplied to the motor to provide an indication of motor torque. Switches (46,47) define preset torque limits for the valve. If the limits are exceeded, a signal is fed to control logic (41) which operates switches (18) to control the supply current to the motor. The speed signal from the Hall effect switches is also fed to a counter (31) to develop a count representative of movement of the valve. The output of counter (31) is compared with preset valves defined by switch circuits (37,38) to define limits of travel for the valve.

Abstract: A method for controlling a plurality of electronic switches employed to connect an alternating current voltage source with a motor. The method comprises the steps of generating a signal, directing the signal to each of a series of output lines in sequence, regularly repeating the directing step, conducting the signal from the output lines to the electronic switches to actuate the electronic switches, and continuously resynchronizing the directing of the signal with the voltage cycle of the voltage source.

Abstract: In a static frequency changer controlled by adjusting the time of conduction of the bilateral switching units forming static converters, the time of conduction is split into n time intervals of conduction of respective subdurations adding-up to be equivalent to the effective time of conduction of the controlled switching unit, and such subdurations are spread and distributed throughout the time period of control of the switching unit within the original switching pattern of the converters, thereby to improve the quality of the output and input currents.

Abstract: An induction motor operating system having a pulse width modulation operating system and a time domain signal generating system.The induction motor is operated from the time domain system to provide extremely large motor starting forces compared to the nominal motor force. Opposite ends of each of first, second and third motor windings are connected across a D.C. power supply and individual power supply. Waveforms are supplied to said respective motor windings during a predetermined brief interval. The first waveform, supplied to a first winding, is configured such that current initially flows through the first winding to establish a first magnetic field in the motor. The second and third waveforms are configured so that current is supplied to the second and third windings after establishment of the first magnetic field to establish second and third magnetic fields reacting with the first magnetic field to create a motive force acting on the moving element of the motor.

Abstract: A motor drive system which utilizes the relatively poor storage time or turn-off time of Darlington pair power transistors which have typically been used as the driver elements in inverter motor driver applications. It primarily finds use in multiphase systems, such as the six step three phase inverter. The relatively long turn-off time of the power Darlington provides relatively constant collector current to the motor without the need for additional circuitry to provide constant base drive load. An additional circuit automatically and dynamically tailors the motor torque to the load requirements to minimize unnecessary use of electrial energy.

Abstract: A motor control system for AC motors utilizing an inverter which is switched to provide pulsewidth modulated DC voltage to be applied to the motor in phase sequence. The pulsewidth modulation is a function of an input reference signal, a signal dependent on motor current and a boost signal operative at low speeds. The motor voltage is continuously regulated as a function of load to provide the necessary power to drive the load.

Abstract: A controller for an induction motor used as a servo positioner comprises a position control module including a microprocessor with memory for generating a plurality of pulse width modulated waveforms. The module includes an analog to digital converter for converting one of four analog signals into digital signals readable by the microprocessor. The analog signals correspond to a gain signal, a feedback signal, a set point signal and a dead band signal. The module also receives digital signals for programming purposes. The microprocessor is programmed to initialize conditions and convert the analog signals.The module is included in a three phase drive controller which has drivers connected to the module for receiving the waveforms and generating corresponding AC inputs to the three phase motor. An overcurrent detector is provided for sensing overcurrents in the AC signals and for generating an interrupt signal which is applied to the module for interrupting the function thereof.

Abstract: A power control circuit for a three phase induction motor wherein power factors for the three phases are summed to provide a control signal, and this control signal is particularly filtered and then employed to control the duty cycle of each phase of input power to the motor.

Abstract: A motor control system controls to be constant a reactive power consumed by a motor load equipment having a motor to be driven by power supplied from an AC power source and a couple of thyristor converters for regulating the power supplied to the motor. To this end, the motor control system is comprised of a reactor power detector for detecting the reactive power of the motor load equipment, a command circuit for issuing a command to specify the rated reactive power consumed in the rated load running of the motor load equipment, and a reactive power control unit which receives an output signal from the command circuit and an output signal from the reactive power detector to produce a firing phase command signal depending on a difference between them. The firing phase command signal from the reactive power control unit is applied to an automatic pulse phase shifter to control the firing phase of the thyristor converters.

Abstract: A system for driving an inductor type synchronous motor for minute control thereof which includes an inductor type synchronous motor having a circuit for driving m phases of driving windings and first magnetic teeth. A second group of magnetic teeth is provided facing the first group of magnetic teeth. Apparatus is provided for feeding electric current from a DC power source to the driving windings of the respective phases. The driving winding for one phase intersects the flux of a partial set of first magnetic teeth or at least two magnetic teeth to provide a flux-interlink. A group of solid state switches are interposed between the source for producing the electric current and the driving windings of the respective phases. A distribution pattern generator generates patterns in response to a command signal and controls the on-off states of the solid-state switches with the noted patterns to thereby form the electric current into trigonometric-functional-patterns.

Abstract: A control unit for a converter has a circuit for the formation of a periodic control signal having a given pulse pattern including a memory in which code words designating the position of the switching pulses (flanks) of the control signals in one period or subperiod of the converter voltage, divided into a number of increments, are stored. Address input of the memory is connected to an addressing unit which generates addresses associated with the pulse pattern of the control signal and with the switching pulses within the pulse pattern. A digital comparator compares the code words at the output of the memory with the count of a counter. Whenever the code word and the count are in agreement, the comparator triggers a pulse stage generator whose output signal represents the control signal and advances the addressing unit to the next address. The invention makes possible the formation of control signals independent of circuit for different converter types and converter circuits is thus made possible.

Abstract: Disclosed is an AC motor drive system having a variable frequency, variable magnitude AC current supplied from a controlled inverter coupled to a variable DC current source in the form of a converter by way of a DC link including an inductor. The AC motor load is controlled so as to have dual modes of operation in order to optimize torque at any speed which can be produced within the voltage and current limitations of the variable frequency power source. The first mode comprises a constant slip or constant angle mode for operating speeds up to the corner point speed which is defined as the speed at which the motor voltage at full torque matches the maximum voltage the variable frequency inverter coupled thereto can provide. Thereafter, the system enters the second mode by automatically shifting to a constant horsepower variable slip or changing angle mode for operating speeds beyond the corner point speed.

Abstract: A power control circuit for an induction motor wherein a servo loop is used to control power input by controlling the power factor of motor operation, and wherein the power factor is measured by summing the voltage and current derived square wave signals.

Abstract: To achieve synchronization of an inverter-synchronous machine drive system, feedback of a phase angle signal, derived in part from stator current drawn by, and voltage supplied to, the synchronous machine, is provided to control the frequency of inverter thyristor conduction. At light or zero synchronous machine load conditions, machine stator current may be of insufficient magnitude to permit derivation of the phase angle feedback signal; therefore, substitute simulated stator current signals, proportional to a preselected combination of inverter thyristor gating pulses, are utilized to derive the phase angle feedback signal, thereby allowing inverter-synchronous machine drive synchronism to be maintained.

Abstract: A circuit and method is disclosed for detecting the presence of charges of appropriate magnitude and polarity on commutating capacitors of an inverter that converts a DC output current to a drive current of variable magnitude and frequency for driving an AC electric motor producing controllable rotation and torque. The presence of charges of appropriate magnitude and polarity is detected by measuring the voltages across the conduction controlled rectifying devices in the inverter. In addition, the existence of conduction controlled rectifying devices in the conducting state is determined by measuring the magnitude of the DC output current. An output signal is generated when the charges of appropriate magnitude and polarity are detected, which output signal is effective to allow the inverter to generate normal drive current.

Abstract: An a-c induction motor powered from an adjustable frequency and adjustable magnitude power source is provided with a feedback control system whose gain is varied as a function of the magnitude of flux developed in the motor in order to normalize system response throughout the motor operating range. The control system is a two-loop system in which one loop adjusts excitation frequency and the other loop adjusts excitation magnitude with the excitation frequency loop being responsive to a torque command signal and a torque feedback signal to generate an error signal which is utilized to adjust the excitation frequency of the power source. System gain is varied by modifying the error signal as a function of the magnitude of flux developed in the motor. Preferably this modification is performed by dividing the error signal by a signal representative of the magnitude of motor flux.

Abstract: A motor operated valve, typically a butterfly valve driven by .[.a synchronous.]. .Iadd.asynchronous .Iaddend.electric motor (16), is provided with a torque sensing arrangement wherein an cyclic electrical signal representative of the rotational speed of the motor is produced by magnets (22) on disc driven by the motor and Hall effect switches (23,24). The frequency of this signal is compared in a circuit (43) with the frequency of current supplied to the motor to provide an indication of motor torque. Switches (46,47) define preset torque limits for the valve. If the limits are exceeded, a signal is fed to control logic (41) which operates switches (18) to control the supply current to the motor. The speed signal from the Hall effect switches is also fed to a counter (31) to develop a count representative of movement of the valve. The output of counter (31) is compared with preset valves defined by switch circuits (37,38) to define limits of travel for the valve.