Abstract: A control circuit for driving an induction motor wherein an AC voltage is converted into a direct current by a rectifying circuit and the direct current is converted into a signal having a variable voltage and frequency by a transistor inverter connected in parallel with a smoothing capacitor, and a regenerative circuit is connected in parallel with the inverter, and a first monitoring circuit is provided for comparing the terminal voltage V.sub.C of the smoothing capacitor and a first reference voltage E.sub.1 when braking is to take place. When the condition V.sub.C .gtoreq.E.sub.1 exists, the transistor inverter is disabled but the regenerative circuit is allowed to operate. When the condition V.sub.C <E.sub.1 exists, the transistor inverter is operated in the regenerative braking region. A second monitoring circuit is provided for comparing the smoothing capacitor terminal voltage V.sub.C and a second reference voltage E.sub.2 (E.sub.2 >E.sub.1). When the condition V.sub.C .gtoreq.E.sub.

Abstract: In a method and apparatus for controlling a speed of an AC motor energized by a source of alternating current through a frequency converter, a limiter responsive to input voltage and input current is provided for decreasing a primary frequency at a rate faster than a rate of decrease in a number of revolutions of the motor when the source is interrupted for a short interval and for accelerating the motor with a primary current thereof limited to a predetermined value while maintaining the primary frequency and the primary current in a predetermined relation.

Abstract: A control circuit for an induction motor powered system wherein a power factor controlled servo loop is used to control, via the phase angle of firing of a triac (16), the power input to the motor (14) as a function of load placed on the motor (14) by machinery of the powered system. Then, upon application of torque by this machinery to the motor (14), which tends to overspeed the motor, the firing angle of the triac (16) is automatically set to a fixed, and relatively short, firing angle.

Abstract: A standard, unmodified AC induction motor has its stator winding energized from a sine wave source through a signal-responsive wave modifier operative to control the portion of each cycle of the sine wave which is coupled from said source to the stator winding. An improved motor current demodulator, responsive to efficiency-related parameters and excessive stator winding inrush current each time said current increases from zero, produces signals for controlling the wave modifier, thereby to maintain optimum motor efficiency with varying motor loads and power source variations, and the signals also control a motor protector circuit which inhibits said wave modifier thereby to deenergize said stator winding under excessive input current conditions, excessive motor temperature or a potentially damaging combination thereof.

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. While the attenuation may be a continuous linear function of speed, a switch (Q.sub.1) is employed to provide a step change in attenuation at 40% of speed.

Abstract: A commutating device for driving a load wherein a main supply voltage is converted into positive and negative buffer voltages which are converted into a control voltage for application to at least one load and wherein the frequency of the control voltage is controlled by means of commutation of the buffer voltages by means of a main thyristor and a commutation circuit including an auxiliary thyristor provided for each of the positive and negative buffer voltages. At least one additional commutation circuit including an auxiliary thyristor, and typically plural additional commutation circuits, are connected in parallel to the firstly noted commutation circuit with the conduction periods of the several commutation circuits being determined on the basis of the polarity and level of the current to the load.

Abstract: A failure detector is provided for detecting unidirectional failures in triacs, particularly as used in power factor controllers for induction motors. In a first embodiment, the triac voltage waveform is sensed and upon detection of an unbalanced signal, corresponding to failure of the triac in either the positive or negative direction, the triac is turned full on in both directions. In a second embodiment, a pair of pulsed signals are derived, the pulse durations of which are proportional to the phase difference between the load current and voltage for each half cycle, and the triac is turned full on responsive to a difference in pulse duration between the half cycle signals. An unidirectional open circuit detector is adapted to use a signal from either of the first and second embodiments to turn the triac off in response to an open circuit failure in either direction.

Abstract: SCR devices replace the usual diodes of the rectifier bridge section of a wound-rotor slip-recovery system motor drive. By controlling the retardation angle of the SCR devices while controlling the line bridge for acceleration from zero speed to normal speed, the rating of the overall system is reduced. By removing the gating signal of the SCR's while operating at a retardation angle in the range between zero and 90.degree., operation is immediately brought to a stop in case of an emergency.

Abstract: A variable speed controller for an alternating current induction motor reestablishes the start time for firing pulses and clock pulses in a circuit having a uniform frequency generator generating firing and clock pulses. Feedback from the stator terminals sets an oscillator with a sawtooth type ramp output. Subsequent feedback from the stator terminals are compared with the output of the oscillator in a comparator that establishes a time or phase shift in the generated output having the same frequency, for resetting the firing pulses so that the frequency of current to the stator winding is a function of the relationship between the stator and rotor positions, and of the current amplitude in the stator windings. Adjustment of the circuit parameters reduces the difference between the rotor and stator positions and optimizes stator current to maintain flux balance.

Abstract: There is disclosed a current type inverter excellent in transient response which comprises a two-phase sine wave generator for receiving signals corresponding to a motor speed signal and a speed deviation signal, to provide sine waves shifted 90.degree. in phase, and a vector calculating circuit for calculating stator current instruction vectors from exciting current components and torque current components, the outputs of the vector calculating circuit being applied as frequency instruction signals of a conventional current type inverter.

Abstract: A switch, that appears the same as an ordinary snap switch, is shown with a positive ON and a positive OFF with a variable control circuit therebetween. The variable control circuit includes a triac gated through a diac to give an infinite control range that depends upon the point at which the triac is triggered. In using the variable control circuit of the switch, a shunt or a bypass is provided for the gate of the triac through a full wave bridge rectifier circuit for a predetermined time interval. The time interval is determined by an RC time constant connected across the bridge. Therefore, for the aforementioned predetermined time interval, essentially a full wave AC voltage is passed through the triac to a load. For motors, this allows the motor to come up to speed prior to subsequently reducing the speed of the motor by the variable control circuit after the predetermined time interval.

Abstract: The secondary voltage of a wound-rotor induction motor is rectified by a multi-phase full-wave rectifier circuit of Gratz connection. An inverter connected to the full-wave rectifier circuit through a DC intermediate circuit regulates the amount of AC voltage fed back to the AC power source thereby controlling the speed of the induction motor. A smoothing reactor is disposed in one of the DC buses of the DC intermediate circuit, with its inverter-side terminal being connected to at least two of the AC-side terminal of the full-wave rectifier circuit through series circuits of a resistor and thyristors. A DC gate signal is applied to the thyristors in the series circuits upon detection of interruption of AC power supply, and application of the DC gate signal is ceased in a predetermined period of time after recovery of the AC power supply voltage. The system of simple structure can thus prevent commutation failure of the inverter even when the supply of the AC power supply voltage is interrupted momentarily.

Abstract: The braking of an a.c. motor is accomplished by sequence controlled outputs of a shift register circuit which sequentially disconnects the main a.c. electrical excitation from the a.c. motor, connects a full wave rectifier circuit to the a.c. motor and then applies the a.c. electrical excitation to the full wave rectifier circuit resulting in a braking current being supplied to the a.c. motor.

Abstract: A control apparatus is disclosed for an electric car having an induction motor supplied with polyphase AC power of variable frequency from a power converter so as to drive a driving wheel. This control apparatus comprises a detector for detecting the actual running speed of the electric car irrespective of whether the driving wheel causes adhesion or non-adhesion, a device for establishing a slip frequency of the induction motor, and a device for generating a frequency command based upon a signal of the actual running speed and the slip frequency, this frequency command being used to control the output frequency of the power converter.

Abstract: A synchronization arrangement for delaying excitation of the field winding (5) of a brushless synchronous motor until the motor rotor has run up approximately to synchronous speed in which the appropriate moment for applying the field excitation is determined by monitoring two signals respectively representative of the currents in two rectifying devices (11, 15) separately connected, oppositely poled, across the motor field winding.

Abstract: A torque control for an electromechanical torquing device of a type wherein there occurs variable clearance between a rotor and field. A Hall effect device senses the field present, which would vary as a function of spacing between field and rotor, and the output of the Hall effect device controls the power applied to the field so as to provide a well-defined field and thus a controlled torque to the rotor which is well-defined.

Abstract: An energy-saving device in the controlof an induction motor which keeps the power factor to a desirable value, regardless of load and line voltage variations, by switching off the voltage applied to the motor during each cycle for a period of time in response to the phase lag between current and voltage. An automatic timing circuit provides for the application of maximum power during motor starting and quick response upon sudden changes in load conditions.

Abstract: A method and control apparatus are disclosed for maintaining a measured parameter of an environment in a closed-loop system within a range of the desired level for that parameter, to an accuracy greater than that of the parameter measuring device in the closed-loop system. The control apparatus periodically receives measurement readings of the parameter to be controlled from a sensor, having a fixed measurement accuracy. An adjustable length memory stores a historical value of changes between the periodically obtained parameter measurements that have occurred over a predetermined length of time. The control apparatus and method generates a control signal for regulating a prime mover acting on the environment which affects the measured parameter, by combining the historical value change data stored in the memory with the difference between a current parameter measurement and the desired parameter value.

Abstract: A motor control circuit controls the speed of a single-phase split capacitor or shaded pole electric motor, and permits operation of the motor over a wide range of speeds without stalling. A first gated bilateral switch such as a triac is connected in series with the motor, and is fired by an integrating circuit through a second bilateral switch such as a diac. The integrating circuit charges through the start winding of the motor and a potentiometer which adjusts the rate of charging of the integrating circuit for the minimum speed setting desired. The motor control circuit also includes a temperature sensing bridge which becomes unbalanced as a function of increasing temperature. A light emitting diode connected to the bridge emits light as a function of the unbalance of the bridge.

Abstract: Cooling means for cooling a control such as for use in controlling the operation of electric vehicles or the like. The control utilizes a direct current battery power supply and includes an inverter for delivering alternating current to an alternating current motor of an air moving structure, such as a fan, provided for cooling the control during the operation thereof. The circuit is arranged to cause the fan to have variable power as a direct function of the load demand of the control circuit so that maximum cooling occurs when the load demand in the control is maximum and minimum cooling occurs when the load demand is minimum. The circuit is arranged to maintain an effectively constant volt-second duty cycle characteristic at the control power supply to the air moving structure whereby the variation in power developed by the motor thereof is a function of the duty cycle characteristics of the control power supply as applied to the motor.

Abstract: The logic control system of the invention regulates the frequency of operation of an inverter which drives an electric motor, and also regulates the level of the d-c bus voltage supplied to the inverter. This is accomplished by sensing the level of the bus voltage and the level of the current supplied to the motor, and comparing the sensed values to a reference or set point signal. The motor drives a compressor, and a capacity control system cooperates with the logic control system in the regulation of the compressor. The capacity control system provides signals, such as start/stop and inverter set point, to the logic control system to assist in regulating operation of the inverter which drives the compressor. In particular the logic control system includes a reference conductor on which a basic reference control signal is developed for use in controlling both the amplitude and the frequency of the a-c energy supplied by the inverter to the motor.

Abstract: In an assembly of a work-performing machine having variable torque demand driven by an asynchronous motor, a phase-angle control device for varying the operating voltage of the asynchronous motor in accordance with the respectively required torque, the asynchronous motor being operable with substantially optimal efficiency, by means of said phase angle control device, with the operating voltage matched to the respectively required torque.