Abstract: A PWM, controlled current, voltage source inverter controls an induction motor in response to signals from a power factor control circuit. The power factor control circuit receives signals related to motor terminal voltages and multiplexes them to a comparator. The inverter and multiplexer are sequenced each time the comparator input reaches a reference level. The frequency of the inverter is thus self generated. The power factor of the system can be controlled to implement a variety of control strategies.

Abstract: A phase-detector (16, 18, 20) is provided for use in a power factor controller for a three-phase induction motor. The power factor controller includes switching thyristors (10, 12 14) for each motor phase winding and the phase detector for each phase includes an operational amplifier (36) which senses the current phase angle for that phase by sensing the voltage across the phase thyristor. Common mode rejection is achieved by providing positive feedback between the input and output of the voltage sensing operational amplifier.

Abstract: An AC motor control method and apparatus therefor, for controlling an AC motor 11 by holding the excitation current I.sub.0 of the AC motor 11 constant and varying primary current I.sub.1 in accordance with a speed deviation .DELTA.n. Stored previously in a memory device 18 are a torque T-slip frequency .omega..sub.s characteristic, a slip frequency .omega..sub.s -primary current vector I.sub.1 characteristic, and a slip frequency .omega..sub.s and phase .phi..sub.1 characteristic which take secondary leakage reactance into account. Slip frequency .omega..sub.s, primary current vector I.sub.1 and phase .phi..sub.1 are read out of the memory device in accordance with the torque command T obtained from the speed deviation .DELTA.n, whereby three-phase current commands i.sub.u, i.sub.v, i.sub.w are produced. Accordingly, torque irregularity is suppressed and an excellent response obtained.

Abstract: A drive system for a polyphase induction motor for extending the range of high frequency operation has two current source inverters connected to the polyphase motor to supply power to the motor. Motor speed and motor load are sensed and a circuit responsive to increasing motor speed and decreasing motor loads advances the firing pulses of one inverter while delaying the firing pulses of the other inverter. The advance in firing of one inverter and the delay in firing the other, reduces the effective current supplied to the motor while not decreasing the current available in each inverter for commutation.

Abstract: A scalar control supplemented by a decoupler transfer function control is provided to develop frequency and current commands for a current controlled inverter driving an induction machine. The machine torque is controlled by the slip and corresponding torque producing component of stator current. The rotor flux is maintained constant by the flux component of stator current. The total stator current is controlled to hold rotor flux constant with desired torque during steady state conditions and the decoupler compensator varies stator current to maintain rotor flux constant during transient conditions.

Abstract: A voltage or current balancing control for supplying a balanced three-phase alternating current supply to an electrical three-phase load. Three controllable full wave semiconductor gates respectively feed one phase of a three-phase alternating current supply to the electrical load. The semiconductor gates are adapted to controllably adjust the voltage or current of a phase of the supply in accordance with a gate control signal to be applied thereto. A comparator circuit is connected to receive the three-phase alternating current supply and is adapted to compare either the voltage or current characteristics, or both (power) of each phase to determine an unbalanced condition therebetween which is analyzed by an analog or digital computer, which accordingly supplies gate control signals to the semiconductor gates respectively to independently control them in accordance with the unbalanced condition to adjust the voltage and/or current of all three phases of the supply to an equal or balanced condition.

Abstract: Control system for driving a synchronous motor at a speed greater than a rated speed with a rotational speed detector for the rotor mounted on the motor, rotational position detector for detecting the rotational position of the field pole of the motor, an error signal generator which produces the difference between a desired speed signal and an actual rotational speed signal, and a calculating device for calculating armature current component values Id, Iq and power-factor .phi..

Abstract: A load commutated inverter synchronous motor drive system wherein a thyristor firing control of the inverter is determined by the amplitude of pesudo flux waveforms which are derived from the integral of the line voltages coupling the inverter to the motor being driven. A firing strategy is provided based on the premise that optimum thyristor firing in a load commutated inverter operating at a leading power factor occurs at a point just below the peak of the forthcoming pseudo flux waveform which point comprises an amount of volt-seconds necessary to effect current commutation plus a nominal safety margin. The determination and control is implemented, preferably, in a software phase lock loop but can, when desirable, be implemented in hardware.

Abstract: The load side converter or inverter in a load commutated inverter motor drive, including a source side AC to DC converter coupled to a DC to AC converter via a DC link circuit, is adapted to have at least three and preferably four modes of operation for bringing an AC motor load, and more particularly a synchronous motor, up to speed. In the preferred embodiment, the first mode constitutes an idle mode wherein the converter thyristors are maintained in a non-conducting state until commanded for normal operation. The second mode constitutes an initial start-up mode which assumes no knowledge of initial rotor position of the motor and simply utilizes a fixed low frequency firing signal to sequentially gate the thyristors using forced commutation to commutate the off-going thyristor.

Abstract: The invention relates to an inverter circuit for operating a speed-controllable asynchronous motor. The inverter circuit is of the type wherein the voltage and frequency are substantially proportional until the nominal frequency has been reached at nominal voltage. The circuit includes and inverter, a desired value control, a D.C. voltage supply with a voltage regulator which sets the voltage depending on the desired value, and a voltage-operated frequency regulator. The circuit can be operated at frequencies above the nominal frequency to avoid damage to the inverter which would otherwise be caused by (1) high voltage due to the motor operating as a generator or by (2) the rapid reduction of the speed setting controls which is not accompanied by a corresponding drop in the voltage supplied to the inverter.

Abstract: A pulse generating system for providing firing pulses to selectively trigger solid state control devices connected to a three-phase A.C. line system, and more specifically to trigger said devices in selected relation with respect to the phase and frequency of the A.C. line.

Abstract: A control for establishing a rotating field in a single phase AC induction motor (10) having a rotatable output and first (12) and second (14) sets of mechanically displaced windings which are energized alternately and cyclically by a single phase AC input for establishing the rotating field to effect rotation of the output. The control includes a single phase AC input, first and second solid state switch means, 18, 20, for interconnecting the first and second sets of windings, respectively, of the motor with the AC input. The first and second switch means when conductive apply energy from the input to the first and second sets of windings, respectively, and when non-conductive prevent the application of energy from the input to the first and second set of windings, respectively.

Abstract: A synchronous motor drive includes an inverter gating control system using three counters wherein two counters respond to 180.degree. apart zero crossings for providing units of time in terms of clock units, and the third counter is at a computed time interval preset with a count to be counted down to derive the remaining time which is to elapse until a predetermined firing angle is reached, at which time firing of the thyristor of the inverter is triggered.

Abstract: A control for an A.C. motor operates to feed a high average value of voltage to the motor during a starting period of predetermined duration and to then automatically switch the voltage supplied the motor to a lower average voltage of substantially fixed value. This lower value of average voltage is determined without feedback to the control circuit. The control may be designed for use with single phase or multiple phase motors and for motors of various different power ratings.

Abstract: A control system for an AC motor drive including a source side converter and a load side converter coupled together by means of a DC link circuit wherein the current in the DC link circuit is controlled by either the source side converter or load side converter depending upon which converter is capable of control. This is achieved by crosstieing a signal from the normal regulating path in the source side converter control to the alternate regulating path in the load side converter control. This signal is chosen to be indicative of the source side converter controller being unable to control current, and may be derived from current error. This signal operates to alter the firing angle of the load side thyristor bridge to regulate the DC link current in the event the source side converter is unable to maintain the required current regulation.

Abstract: A static frequency changer for feeding a synchronous machine and composed of a mains side static converter, a machine side static converter and a direct current intermediate circuit connected between the converters, is further provided with an additional static converter connected at the machine side in parallel opposition to the machine side static converter, and a direct voltage capacitor connected in parallel to the additional converter.

Abstract: An adaptive control system for improving the efficiency of an electric motor. Connected in series with the motor and across the voltage supply is an electronic bi-directional switch which may be triggered at differing times relative to the zero-crossing of the AC supply to thereby control the amount of time during each cycle that the motor is energized. The firing angle for the electronic switch is determined by an optimizing network which functions to introduce a relatively low frequency perturbation in the firing angle and means for sensing the effect of that change on the average power being drawn by the system during the period of the perturbation. If this small, periodic change in the firing angle of the electronic switch results in a decrease in average power consumption, the firing angle is adjusted in a direction which is determined to have precipitated the improvement. Alternatively, if the shift in firing angle occasioned by the minute perturbation resulted in a worsening of motor performance, i.e.

Abstract: A power factor type motor controller in which the conventional power factor constant voltage command signal is replaced during a starting interval with a graduated control voltage. The present invention adds to the three-phase system of pending application Ser. No. 199,765, filed Oct. 23, 1980, means for modifying the operation of the system for a motor start-up interval of 5 to 30 seconds. The modification is that of providing via ramp generator 174 an initial ramp-like signal which replaces a constant power factor signal supplied by potentiometer 70. The ramp-like signal is applied to terminal 40 where it is summed with an operating power factor signal from phase detectors 32, 34, and 36 to thereby obtain a control signal for ultimately controlling SCR devices 12, 14, and 16 to effect a gradual turn-on of motor 10.

Abstract: An inverter controls an induction motor in response to signals from a power factor control circuit. The power factor control circuit receives signals related to motor terminal voltages and multiplexes them to a comparator. The inverter and multiplexor are sequenced each time the comparator input reaches a reference level. The frequency of the inverter is thus self generated. The power factor of the system can be controlled to implement a variety of control strategies.

Abstract: A control system for a permanent-magnet motor (10) driven by a multiphase line-commutated inverter (12) is provided with integrators (24) for integrating the back EMF of each phase of the motor for use in generating system control signals for an inverter gate logic (30) using a sync and firing angle (.alpha.) control generator (26) connected to the outputs of the integrators. A precision full-wave rectifier (16) provides a speed control feedback signal to a phase-delay rectifier (14) via a gain and loop compensation circuit (20) and to the integrators for adaptive control of the attenuation of low frequencies by the integrators as a function of motor speed, whereby as the motor speed increases, the attenuation of low frequency components by the integrators is increased to offset the gain of the integrators to spurious low frequencies. The .alpha.-control signals are produced by the firing angle control generator by means (48, 50) for combining 120.degree.

Abstract: Disclosed is an apparatus for controlling the rotational speed of an electric motor based upon the load encountered by the electric motor. A load sensor provides a voltage level based upon the operating load of the electric motor and accumulates this voltage in accordance with the cycle of the alternating current supplied to the motor. If during a cycle of the alternating current, the voltage exceeds a predetermined level, a transistor will be biassed into conduction, said transistor turning off a thyristor and preventing any further conduction of the thyristor during that cycle of the alternating current. Thus the duty cycle of the thyristor determines the total amount of current supplied to the electric motor and this current level determines the rotational rpm of the motor.

Abstract: A three-phase power factor control system for an AC induction motor (10) monitors the power factor of a first-phase motor winding and produces a rectangular-wave pulse power-factor signal (f) which is used to directly control the duration of "on" time of each cycle of input power to the first-phase winding and to indirectly control the "on" time of each cycle of input power to second- and third-phase windings. To provide a signal for controlling the power to second- and third-phase windings the power-factor pulse signal is synchronized with a square-wave oscillator (30) whose frequency is three times that the power-factor pulse signal. Each second and third positive pulse (38 and 40) of the square-wave oscillator (30) is used to control the "on" time of each cycle of input power to the second- and third-phase windings.

Abstract: SCR devices replace the usual diodes of the rectifier bridge section of a wound-rotor slip-recovery system motor drive, and by selection of the retardation angle of the SCR's between either zero or close to 180.degree., two-quadrant operation is made possible, which includes reverse torque and reverse rotation, while controlling the retardation angle of the power line bridge of SCR's.

Abstract: A multi-phase motor controller for controlling voltage and power expended by a multi-phase motor comprises a sensing stage for detecting power factor angle, a feedback amplifier stage for comparing the power factor angle with a desired power factor angle, and a control stage for controlling voltage and power expended by the multi-phase motor in accordance therewith. Other features of the motor controller include a current limiting circuit for limiting "in-rush" current during "start up" of the motor controller, a current trip circuit for implementing "instantaneous trip" and "timed trip" capabilities upon detection of corresponding "overload" conditions, and a phase-loss circuit for automatically disabling operation of the motor upon detection of "phase-loss". A further embodiment of the motor controller includes a lead network, connecting the feedback amplifier stage to the control stage, for enhancing the stability of operation of the motor controller.

Abstract: An asynchronous motor drive comprising a transmitter (1) of position of the rotor of the asynchronous motor whose stator windings (6) are connected to an active stator current setter (22) and a reactive stator current setter (20) through a number of series-connected units which include a controlled current source (7), a phase-sensitive rectifiers unit (9), an adder (25), multipliers (17 and 18) and a phase converter (13). Inputs (11) of the unit (9) are connected to outputs of a multiphase voltage source (12) which comprises, in a series arrangement, a reference frequency setter (30), a frequency adder (31), a frequency divider (32), a phase converter (33) whose outputs are connected to the inputs (11) of the phase-sensitive rectifiers unit (9), and a controlled rotor current frequency generator (34). The generator (34) has its output connected to the input of the frequency adder (31).

Abstract: A control system for an induction machine. The system includes a multiphase variable frequency oscillator adapted to provide at least one pair of signals having frequencies proportional to the sum of a desired slip frequency and the frequency of rotation of the induction motor shaft, where the signals are in phase quadrature. A weighting network amplitude-scales one of each pair of signals by a factor related to the desired slip frequency. A summing network then generates an excitation signal for each stator winding by summing the amplitude-scaled signal and its associated quadrature signal corresponding to that stator winding.

Abstract: An electric control apparatus of an induction motor is provided with a flux current controller for controlling the flux current of the motor and a secondary current controller for controlling the secondary current of the motor. A pulse generator circuit is disposed to control the amplitude, frequency and phase angle of the primary current of the motor according to output signals of the flux current controller and secondary current controller. The primary voltage and frequency to be applied to the motor are controlled by pulse signals from the pulse generator circuit. This pulse generator circuit includes a primary voltage setting zone for setting the primary voltage of the induction motor and a primary voltage detecting zone for detecting the primary voltage of the motor.

Abstract: Two inverters in series in the DC line of a slip-recovery motor drive of the SCR controlled type are asymmetrically controlled to allow reduced current reflected back in the transformer. Two secondaries in the transformer are associated with the respective inverters. Reduced rating of the transformer, reduced saturable reactor in the DC link and improved power factor are direct advantages of such arrangement.

Abstract: A slip-recovery AC motor drive includes two inverters connected in series between the DC link terminals derived from the rectifier coupled with the rotor, and the thyristors are controlled asymmetrically between pairs of half-bridges pertaining to different inverters, thereby to by-pass the output of one inverter alternately during successive equal time intervals of conduction. The recovery transformer has two secondaries each connected to a corresponding inverter output.

Abstract: A phase-triggered, gate-controlled AC semiconductor switch, in series with an induction motor and its AC supply, optimizes power flow to the motor under changing mechanical load conditions by varying the amount of supply voltage applied to the motor over each half-cycle of the AC supply. Such power flow optimization is effected by utilization of a control voltage generated by the freewheeling induction motor during nonconduction periods of the switch. The triggering point of the switch relative to the preceding zero crossing point of the supply voltage, that is, the switch firing angle or delay angle, is varied by the control voltage augmenting to a varying degree the charging rate of a capacitor that triggers the semiconductor switch into conduction.

Abstract: An alternating current machine drive system, comprised of an alternating current machine and an inverter configured of a plurality of pairs of transistors with the transistors of each pair coupled in series-aiding fashion and each of the pairs of serially coupled transistors connected across a direct current source, is controlled in accordance with inverter current. The transistors of each inverter transistor pair are alternately rendered conductive to supply alternating current at the inverter output in accordance with a current error signal, proportional to the difference in magnitude between actual inverter phase current and a sinusoidal reference signal, with the conduction state of the transistors of each pair reversing each time the current error signal exceeds an upper and lower hysteresis limit, which limits vary in accordance with actual inverter phase current.

Abstract: By controlling the phase angle at which conduction occurs in the SCR's in an SCR rectifier bridge, a d-c voltage of adjustable magnitude may be produced from a-c line voltage applied to the bridge. The specific angle at which the SCR's are fired into conduction during each half cycle of the a-c line voltage is determined by comparing a ramp-shaped pulse, produced from the line voltage during each half cycle, with an error signal which varies as a function of the difference between the desired d-c magnitude and the actual amplitude of the d-c voltage. The d-c power supply is made immune to line voltage variations by regulating the ramp-shaped pulses so that they always have the same pulse width regardless of line voltage amplitude, thereby facilitating precise control over the d-c magnitude.

Abstract: A variable frequency power supply device supplies an AC power to a squirrel-cage motor through an AC parameter control. The control receives a command active current resulting from a command torque and a command exciting current to generate a resultant current and its phase. The command torque is produced from the actual and command motor speeds and the exciting current is caused from the actual motor speed. The control also receives a command frequency determined by the actual motor frequency and a command slip frequency also resulting from the command torque. The control controls the firing phases of thyristors in the power supply device in response to the command current, phase and frequency. The control may generate a voltage for supplying the active current and an exciting voltage to similarly control the firing phases of the thyristors. In the latter case, the exciting voltage may be added with its differential to compensate for a rapid change in active current.

Abstract: First to fourth windings are fitted in the slots of each phase of a three-phase AC motor. Those windings are connected in series to silicon controlled rectifiers (SCRs), respectively. The first and second windings having the SCRs form a first antiparallel circuit and the third and fourth windings having the SCRs form a second antiparallel circuit. Three first antiparallel circuits are connected in a delta connection. Three second antiparallel circuits are connected in a star connection with a neutral input terminal. The output terminal of the first three phase AC power supply is coupled with the input terminal of the delta circuit of the first antiparallel circuits and has a voltage lagged by .pi./2 behind the first power supply voltage. The output terminal of the second power supply of a star connection with the neutral point output terminal is coupled with the input terminal of the star circuit of the second antiparallel circuit.

Abstract: A phase-triggered, gate-controlled AC semiconductor switch of the thyrister type in series with an induction motor and its AC supply, optimizes power flow to the motor under changing mechanical load conditions by varying the amount of supply voltage applied to the motor over each half-cycle of the AC supply. The triggering point of the semiconductor switch relative to the preceding zero crossing point of the supply voltage, that is, the switch firing angle or delay angle, is varied as a function of mechanical loading on the motor by means of a load current induced feedback voltage which varies the breakdown or triggering voltage of a two-transistor switch functioning as a variable trigger diode between the gate of the semiconductor switch and a turn-on capacitor charged by the AC supply voltage during non-conducting periods of the semiconductor switch.

Abstract: A load-commutated inverter synchronous machine drive system control apparatus comprises at least one microcomputer for determining optimum or desired values for inverter turn-off time, inverter link current and machine air gap flux from machine drive system voltage and currents. Inverter frequency is regulated in accordance with the difference in magnitude between optimum and actual inverter turn-off time to minimize the inverter turn-off angle irrespective of machine frequency, thereby reducing synchronous machine reactive power. Inverter link current and synchronous machine field current are regulated responsive to the difference in magnitude between optimum and actual inverter link current and the difference in magnitude between optimum and actual machine air gap flux, respectively, thereby assuring machine operation at maximum efficiency.

Abstract: A mooring winch system in which automatic mooring duty is performed by a winch having an AC motor fed from the supply via a converter which includes a DC to AC inverter, the convertor producing a balanced three-phase square, quasi-square, sinusoidal or quasi-sinusoidal output. The motor thus can stall indefinitely, be driven in the sense of rope payout by tension force in the mooring rope, or run in the opposite sense to recover rope, without exceeding its rated temperature for that duty. Rope recovery is adequate both for normal duties and also where higher speeds of recovery are required and rope tension is maintained substantially constant throughout.

Abstract: A control system regulates operation of an electrical motor having multiple stator and rotor coils by regulating the phase displacement (1) between the rotor and stator energizing signals, (2) between the signals passed to the individual rotor coils, and (3) between the signals passed to the individual stator coils. A recorder coupled to the lines over which the phase-regulating signals are supplied to the rotor and stator coils can record these signals for later application to the motor to repeat the initial movement. Additionally displacement of the motor shaft produces signals which can be recorded for later duplication of the original shaft displacement. The phase-regulating signals for the rotor and stator coils can be supplied from a variable frequency oscillator, or a data processor, or any other suitable source.

Abstract: The present invention relates to a control circuit for an A.C. motor with two or several sets of windings. The switch-off phase of the first set of windings is symmetrical with the turn-on phase of the second set of windings, and it is illustrated how to modify the supplied current by simultaneous, symmetrical modification of said phases. As a result a symmetrical field distribution over each pole is obtained even if the turn-on and switch-off phases of the currents supplied to the windings are regulated.

Abstract: A linear servo circuit for A.C. motors is disclosed. The servo circuitry is used in a magnetic tape transport to control the motor which operates a tape reel on which the magnetic tape is stored. The servo circuitry develops two complimentary saw-tooth voltage waveforms synchronized to the sinusoidal A.C. line voltage. One saw-tooth waveform is used to control the motor in the forward direction and the other saw-tooth waveform is used to control the motor in the reverse direction. Comparator circuitry compares the saw-tooth waveforms to a D.C. control voltage which is proportional to the angular position of an arm that controls the tension of the magnetic tape. The comparator circuitry provides a control pulse to a photodiode when the saw-tooth waveform exceeds the D.C. control voltage. Light pulses from the photodiode impinge on a light sensitive SCR which in turn triggers a triac to apply power in the forward or reverse direction to the A.C. tape reel motor.

Abstract: A speed control apparatus includes a plurality of switches disposed between a three phase AC power source and a motor, a low speed control device for feeding power having a frequency lower than the frequency of the power source to the motor under the turn-on control of the switches, and a phase shifting device for shifting the phase order for changing from high speed operation to low speed operation of the motor.

Abstract: In a control system of an alternating current motor energized by a frequency converter including serially connected rectifier and inverter of the type wherein the speed of the motor is controlled by varying the phase of the output current of the inverter by varying the phase of a control signal of the inverter, there are provided a function generator which is supplied with a signal related to the motor torque for generating an analog phase angle signal related to the current phase angle, and a phase shifter responsive to the analog phase angle signal for shifting the phase of the control signal for the inverter.

Abstract: A control system for an a.c. motor having a polyphase primary winding (stator winding) and a corresponding polyphase secondary winding. The primary and the secondary windings are supplied with current from different frequency converters provided separately for each of the windings. The alternating currents flowing through the primary and the secondary windings are in opposite phase with each other. A position detector is provided for detecting the position of rotor of the a.c. motor. The magnitude of the primary current is controlled proportionally to a current reference signal in dependence on deviation of a speed feed-back signal from a speed reference signal, while the magnitude of the secondary current is controlled to a constant value. The phases of the primary and the secondary currents are controlled on the basis of the rotor position.