Abstract: AC induction motor energized by an inverter coupled with a DC power source. Upon shutdown of the inverter because of a fault condition or a rail gap between adjacent power sources, if the motor rotating frequency is greater than a minimum frequency then a decreased motor voltage is applied to the motor and increased as a ramp over a provided time delay period, after which the motor slip is controlled to provide a desired motor torque that is increased over a subsequent time delay period.

Abstract: A motor driving circuit includes an equivalent power PNP transistor constituted by a Darlington connection of a small-current PNP transistor and a large-current NPN transistor, and a switching regulator of a step-down and variable type is provided between the collector of the NPN transistor and the emitter of the PNP transistor. Electric power loss in the motor driving circuit can be reduced, and the electric power required to operate the motor driving circuit can be saved.

Abstract: In induction motor driven by a voltage-type inverter, the torque current component is determined by detecting a primary current flowing to the induction motor. On the basis of the torque current component determined, the output voltage and frequency of the voltage-type inverter are controlled. Additionally, the rotational speed of the induction motor is estimated on the basis of the detected torque current component and the speed of the induction motor is controlled such that the estimated speed signal coincides with a speed command signal.

Abstract: A frequency converter apparatus is provided with a frequency converter coupled to an AC power supply and to a load. The frequency converter converts an AC input with a given input frequency into an AC output with a given output frequency. The frequency converter apparatus is further provided with a frequency reference circuit and a harmonic cancel circuit. The frequency reference circuit supplies a reference signal to the frequency converter so that the output frequency of the AC output follows the reference signal. The harmonic cancel circuit supplies a harmonic cancelling signal to the frequency reference circuit so that the prescribed order of the higher harmonic of the AC output is substantially cancelled according to the frequency, magnitude and phase of the harmonic cancelling signal.

Abstract: AC motor drives which include static inverters typically are operated by inverter controls that are designed according to certain criteria so that the inverter is operated in an efficient manner. Generally, it is desirable to design such a control to reduce as much as possible losses in the motor windings and losses associated with the inverter switches. However, inverters switching losses cannot be reduced without increasing motor losses, and vice versa, since motor losses decrease with increasing PWM frequency while inverter losses decrease with decreasing PWM frequency. In order to overcome this problem, a control system according to the present invention for controlling an inverter which converts DC power into variable frequency AC power for energizing a motor in accordance with an input command includes circuitry coupled to the input command for generating a plurality of waveforms at different frequencies, each frequency being an integer multiple of the frequency of the AC output.

Abstract: For determining the flux vector, an EMF vector (e.sub.s) is formed in an EMF detector (15) from the stator current and the stator voltage, the components of which are determined in a rotating coordinate system rotated by an angle (.beta.) relative to the coordinate system which is fixed with respect to the stator. The flux vector (.psi..sub..beta.) is formed in the rotating coordinate system, taking into consideration the rotary EMF component (e.sub..beta..sup.R) which is generated from the flux vector through rotation by .pi./2 and multiplication by the frequency of rotation (.beta.). The angle of rotation (.beta.) is determined by feeding the direction deviation of the flux vector (.psi..sub..beta.) or a reference vector (.psi.*) for the flux vector by the angle (.beta.) to a servo control (27 or 30, respectively), the output signal of which is fed as the speed of rotation (.beta.) via an integrator (20) for forming the angle of rotation (.beta.).

Abstract: A method of controlling an AC motor which exhibits a constant torque characteristic at a rotational speed N below a base speed Nb and a constant output characteristic at a rotational speed N above the base speed Nb, comprising the steps of finding a base speed N.sub.L after limiting the output power of the AC motor, N.sub.L being derived from the base speed Nb and the ratio .eta. between maximum output power Pmax.sub.1 and maximum output power Pmax.sub.2 before and after the output power of the AC is limited, respectively, rendering the slip frequency of the AC motor constant until the rotational speed N of the AC motor reaches the base speed N.sub.L, varying the slip frequency in inverse proportion to the rotational speed N for N between N.sub.L and Nb (N.sub.L <N.ltoreq.Nb), and varying the slip frequency in proportion to the rotational speed N for N above Nb (Nb<N), whereby the output power of the AC motor is rendered constant at a rotational speed N above N.sub.L.

Abstract: A method and a device for controlling a brushless alternating current motor (23) driven by an inverter (31-36) connected to a direct current supply (24,25). The direct current supplied to the inverter is sensed. The signal is passed through a peak detector (41) to a regulator (45), which decreases its frequency controlling output signal if the peak value input signal exceeds a predetermined value. A control signal corresponding to the torque demand of the motor is also produced. This signal controls the voltage supplied to the motor. Negative pulses at the turning off of the inverter switches are also sensed and used for controlling the degree of magnetization of the motor.

Abstract: This relates to a low cost reliable controller which may be used in conjunction with induction motors or, more generally, to generate AC power from a DC source. The system utilizes a microprocessor in combination with low cost parallel transistors to provide the control function. A feedback module monitors the actual rotor speed and conveys this information back to the microprocessor. A voltage boost module may be used in combination with the microprocessor and switching circuits to optimize the overall efficiency of the system. The microprocessor computes slip and controls the voltage drive in order to further optimize efficiency of the system as a function of motor speed. Both the footfeed voltage and boosted voltage are analog voltages and are applied to an A/D converter. The output of the A/D converter presents a digital representation of the footfeed voltage or boost voltage to the microprocessor.

Abstract: An induction motor is driven by a converter which outputs a variable frequency and variable phase A.C. voltage. The frequency is instructed by a signal which corresponds to a difference between a detected speed signal and set speed signal, a signal which corresponds to a difference between a detected magnetic flux intensity signal and set flux signal, and the detected speed signal.

Abstract: A device for determining a load operating parameter signal, such as the flux of a rotary field machine, has an integrating circuit added at the input of the instrument transformer with a transfer function k/(1+s.multidot.k/.omega..sub.N) that amplifies reduced low frequency load voltage inputs to the transformer to avoid calculation inaccuracies due to the transformer transfer error. Circuitry having the inverse transfer function located at the output of the transformer compensates for the amplification distortion.

Abstract: In a vector control method and system for an induction motor, the decoupling calculation and 2-3 phase transformation are combined to simplify the system configuration, and the plus and minus signs of trigonometric signals are changed according to the rotational direction to enable four-quadrant operation. Further, in the case of a 3-phase induction motor driven by a PWM inverter, the number of the triangular (carrier) wave signals generated during one period of the power supply signal is increased with decreasing frequency of the supply voltage signal to improve the response characteristics when the motor is rotating at a low speed. Furthermore, an initial supply voltage signal with a predetermined frequency is applied to the triangular wave signal generator, when the motor stops, to generate an initial secondary magnetic flux before starting the motor.

Abstract: In a vector control method and system for an induction motor, the decoupling calculation and 2-3 phase transformation are combined to simplify the system configuration, and the plus and minus signs of trigonometric signals are changed according to the rotational direction to enable four-quadrant operation. Further, in the case of a 3-phase induction motor driven by a PWM inverter, the number of the triangular (carrier) wave signals generated during one period of the power supply signal is increased with decreasing frequency of the supply voltage signal to improve the response characteristics when the motor is rotating at a low speed.

Abstract: An induction motor is driven by a power inverter. A torque current command is determined on the basis of a difference between a speed command and an actual speed value. A slip frequency command corresponding to a magnitude of the torque current command is determined, and the slip frequency command and the actual speed value are added together to produce a primary frequency command. An oscillator generates 2-phase sinusoidal signals at a frequency coincident with the primary frequency command which are respectively in phase with the flux axis of the induction motor and 90.degree. out of phase with respect to the flux axis. A torque current pattern signal is produced on the basis of the torque current command and the 90.degree.-out-of-phase sinusoidal signal, and an exciting current pattern signal is produced on the basis of an exciting current setting value and the in-phase sinusoidal signal. Output current of the power inverter is controlled by the two current pattern signals.

Abstract: A quick response vector control method which is one of methods for controlling a speed of an induction motors without a speed detector; in which a voltage of the motor is detected to resolve into a vector component e.sub.d parallel with an exciting current component vector of a primary current and a vector component e.sub.q orthogonal to said exciting current component vector, and a frequency of the primary current is controlled to maintain the vector component e.sub.d at zero, while at the same time the primary current is controlled corresponding to a difference between the vector component e.sub.q and the speed command signal.

Abstract: The present invention generates a motor slip frequency value and two current magnitude values representing quadrature components of the motor stator current to be generated. Closed-loop control of the motor operation is provided by feeding back a signal representative of the motor shaft speed or position calculate the torque required from the motor. The feedback signal is separated into high and low frequency components. Additional circuitry changes the value in response to detected variations in the high frequency components of the feedback signal. The addition of this circuitry causes the motor control circuit to no longer represent the inverse of the motor transfer function network.

Abstract: A current control apparatus includes an instructor for providing a DC amplitude instruction and an AC phase instruction, and a cycloconverter for supplying an induction motor with AC load currents. These load currents are detected by sensors. The sensed signals from the sensors are applied to a detector. The detector generates a DC phase error signal and a DC amplitude signal according to the load currents and the phase instruction. The amplitude instruction, amplitude signal and phase error signal are applied to a comparator circuit. The comparator circuit generates a first voltage instruction and a second voltage instruction. These first and second voltage instructions are applied to a control circuit. The control circuit supplies the cycloconverter with voltage instructions. The comparator circuit, control circuit, cycloconverter, sensors and detector constitute a closed DC feedback control loop which utilizes a vector control method.

Abstract: An AC elevator control system which includes an inverter for inverting a DC voltage to an AC power having a variable voltage and a variable frequency under the control of a command voltage signal and a command frequency signal, and an induction motor which is driven with the AC power to operate an elevator car. With the induction motor operated in the regenerative braking mode, a switching device responds to the actual speed of the car exceeding its command speed to decrease the command frequency signal to such a magnitude that the induction motor has a slip equal to a predetermined one through a first gain regulator connected between a command speed generator and a command frequency generator. Simultaneously a second gain regulator is enabled to equal the command voltage signal to a difference between the actual and command speed signal.

Abstract: A system for operating an induction motor at variable speeds, which is particularly effective when an induction motor is to rotate at a very low speed of several r.p.m. or less. The system produces polyphase sinusoidal signals of a frequency which corresponds to the difference between a command speed and the actual speed of the induction motor, the number of phases of the sinusoidal signals being equal to the number of phases at which the induction motor operates, a sinusoidal carrier wave having a constant frequency of from 50 to 400 Hz and a constant amplitude, and polyphase induction motor drive signals formed by modulating the carrier wave by the polyphase sinusoidal signals. The induction motor drive signals are amplified up to a prescribed value and then applied to the induction motor to energize the stator for each respective input phase so that the rotor of the induction motor will be caused to rotate at a very low speed.

Abstract: A start-up control technique is disclosed for an AC motor. At least one H-switch connects a motor winding to a pair of AC-supplied power lines and is switched between designated states to yield a fundamental frequency component voltage waveform in the winding phase shifted from the voltage waveform in another winding. A rotating field is provided for start-up, without energy-storage phasing capacitors or inductors.

Abstract: A control apparatus for induction motor comprising an induction motor driven by a power converter, a circuit for producing an effective current command value for the induction motor on the basis of a speed command value and an actual speed value, a circuit for producing a slip frequency corresponding to the magnitude of the effective current command value, and a circuit for producing a primary frequency command value on the basis of the slip frequency and the actual speed value, the output of the power converter being controlled on the basis of the frequency command value, the effective current command value and a given exciting current or voltage command value, wherein the control apparatus further comprises a current component detecting circuit for detecting the primary current of the induction motor so as to produce in the form of a DC signal an actual effective current value which is an effective component of the detected primary current, a first current control circuit for producing an effective voltage

Abstract: A simple combinational technique is disclosed using one or more H-switches for start-up control and frequency conversion in an AC motor. A coordinating logic system provides H-switch toggling timing patterns yielding phase shifted voltage waveforms in the motor windings to afford a rotating field during start-up, and provides irregular switching times yielding a chopped sinusoid output waveform of converted frequency for variable speed operation.

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: A method for optimizing the power input to a plurality of parallel connected hysteresis motors wherein a three phase alternating voltage source jointly supplies the motors with an adjustable operating voltage. The method includes measuring, during the operation of each motor, the phase angle difference between motor voltage and motor current and determining the power factor therefrom for each motor. The effective current value of each motor is measured during operation and is combined with the power factor to obtain the active current for each motor. An active current limit value at which each motor transitions from synchronous to asynchronous operation is measured once and stored for each motor prior to commencement of continuous synchronous operation.

Abstract: Disclosed is an apparatus for operating a converted-fed asynchronous electric motor which comprises a flux computer for determining the position of the flux vector from the input values for the stator voltage provided by said motor by solving all the electrical quantities of the Park equations describing said motor in a given position of the rotor axis, taking into account the parameter values corresponding to the rotor resistance and the stator resistance of said motor whereby signals corresponding to the position of the flux vector and belonging to a solution, can be tapped from said flux computer; a converter control unit coupled to said flux computer and said convertor rectifier respectively, forming the control quantities for driving the converter rectifier from the determined position of the flux vector and from the nominal input values which fix the components of the stator current vector parallel and perpendicular to the flux vector.

Abstract: A variable speed motor controller for an AC motor, said controller including a DC to AC converter for providing adjustable frequency AC signals to vary the speed of said motor, and a sensing device and energy saving control for detecting the magnitude of the current signal being supplied to the motor and adjusting the AC voltage to the motor depending upon the magnitude of the current signal. The smaller the motor current being sensed, the smaller the voltage applied to the motor, thereby effecting a saving of energy. Energy is saved using this controller because when the lesser motor current indicates that it is driving less than full load, the input voltage applied to the motor is reduced thereby effecting a power saving.

Abstract: Disclosed is a method to detect the rotor resistance of an asynchronous machine, wherein a first vector attached to the emf of the machine is determined by computing the emf-vector or the flux vector from the stator voltages and the stator currents; wherein a flux attached to an arithmetic model circuit is determined, whereas the arithmetic model circuit uses the stator currents and the rotor position of the machine and an adjustable model parameter for the rotor resistance as basic quantities and imitates the dynamic events leading to the magnetic flux of the machine; wherein a difference of two quantities is determined, wherein the first quantity represents a defining quantity of the first vector attached to the machine and the second quantity represents a respective defining quantity of a second vector derivable from the imitated flux and that the setting of a model parameter is varied until the value of the difference is a minimum, whereas the model parameter corresponding to the minimum of the difference

Abstract: Disclosed is a method and apparatus for operating an induction motor by an inverter of the pulse-width modulation (PWM) type, wherein the slip frequency is calculated from the speed command and the actual motor speed so as to produce the phase compensation signal, and the frequency command for the inverter is produced by adding the phase compensation signal, the slip frequency signal and the motor speed signal. The primary current command is calculated from the slip frequency, the amplitude ratio of pulse-width modulation is calculated basing on the primary current command and the actual primary current, and the inverter is controlled in accordance with the amplitude ratio so as to control the primary current of the induction motor.

Abstract: A scalar control supplemented by a decoupler transfer function control is provided to develop frequency and voltage commands for a voltage 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 in the outer loop to hold rotor flux constant with desired torque during steady state conditions and the decoupler compensator varies stator voltage to maintain rotor flux constant during transient conditions.

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: An optimum efficiency control system for a variable torque/speed rotary a.c.

Abstract: A first static commutator including a first controllable thyristor rectifier and a first thyristor inverter and a second static commutator including a second controllable thyristor rectifier and a second thyristor inverter are provided. First three-phase AC voltage is supplied to the first controllable rectifier, and second three-phase AC voltage 30 degrees out of phase with said first three-phase AC voltage is supplied to the second controllable rectifier. A brushless motor includes first star-connected three-phase windings receiving the output of the first inverter and second star-connected three-phase windings and 30 degrees out of phase with said first three phase windings. During the starting period of the brushless motor the conduction of the first and second satic commutators is switched for every 30-degree rotation of the brushless motor.

Abstract: In a rotating machine converter controlled drive, the EMF vector components formed from the stator current and stator voltage are integrated by means of a-c voltage integrators, the output quantities of which establish the components of the machine flux vector. In the converter control the parallel and normal components of the stator current relative to this flux vector are introduced. The a-c voltage integrators include zero controllers in a feedback circuit, into which the difference between the machine flux components and corresponding model flux components are introduced. The model flux components are calculated in a computing model circuit from the stator current, magnetization current and rotor position.

Abstract: An arrangement for bridging brief network failures in intermediate-link converters converts the kinetic energy in load motors into electrical energy by reducing the frequency of the converter. Such a frequency reduction is performed in accordance with the value of a control deviation signal corresponding to the difference between desired and actual frequencies of operation of the converter. The control deviation signal is produced by the combination of a PI controller which is coupled at its output to an integrator circuit. The integrator circuit controls the frequency and voltage of the converter.

Abstract: An inverter (34) which provides power to an A. C. machine (28) is controlled by a circuit (36) employing PWM control strategy whereby A. C. power is supplied to the machine at a preselectable frequency and preselectable voltage. This is accomplished by the technique of waveform notching in which the shapes of the notches are varied to determine the average energy content of the overall waveform. Through this arrangement, the operational efficiency of the A. C. machine is optimized. The control circuit includes a microcomputer and memory element which receive various parametric inputs and calculate optimized machine control data signals therefrom. The control data is asynchronously loaded into the inverter through an intermediate buffer (38). A base drive and overlap protection circuit is included to insure that both transistors of a complimentary pair are not conducting at the same time.

Abstract: Apparatus for controlling a permanent magnet AC synchronous motor supplied by a forced commutated inverter that does not use a mechanical shaft position sensor. A control loop regulates an inverter frequency and maintains inverter synchronism with the motor using electrical angle feedback signals developed from measured flux signals that have been phase shifted.

Abstract: An apparatus for controlling the operation of an AC motor wherein braking energy at the time of a reduction in motor speed is disposed of by regenerative braking. The apparatus includes a rectifier connected to the AC power source, a smoothing capacitor, a variable-voltage variable-frequency inverter, and a regenerative thyristor bridge circuit connected between the inverter and the rectifier through switching transistors. There is also provided a firing control circuit for controlling the firing of each thyristor in the thyristor bridge circuit and for controlling driving of the switching transistors in synchronism with the firing of the thyristors, the braking energy being fed back to the AC power source when the AC motor undergoes a reduction in speed. The apparatus is small and can be constructed simply and inexpensively.

Abstract: A motor speed control system (controller) for controlling the speed of an AC motor. The invention provides sufficient voltage at low motor speeds to overcome the high resistance of fractional H.P. motors, which effects low speed operation, i.e., the ability to provide constant load torque. With the present invention an output frequency voltage offset is provided in a non-linear fashion so that desired load torque is developed over the entire speed range of the control system.

Abstract: In order to energize a load with an output current generally conforming to a control voltage, trains of firing pulses are alternately applied during respective conduction intervals of a recurrence period to a pair of main thyristors connected to opposite terminals of a balanced power supply which may be a DC source. The main thyristors are quenched, at the ends of their respective conduction intervals, by ancillary thyristors which lie in series with a resonant circuit including a commutating capacitor and alternately receive firing pulses in continuous succession in order to keep that capacitor operatively connected at all times to one or the other terminal of the power supply. The transmission of firing pulses to the several thyristors is timed by a logic circuit under the control of a comparator to which the control voltage is fed together with a sawtooth voltage establishing the aforementioned recurrence period.

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: 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: Electric motor control apparatus includes a variable-frequency oscillator 10, a counter 11 clocked by the oscillator, and signal generating means 12 arranged to generate two sinusoidal voltages in quadrature with one another. The two voltages are applied through separate amplifiers 22, 23 to separate stator windings 24, 26, of the motor, the stator windings being 90.degree. apart. Control means includes a bistable circuit 28 producing a signal lagging 45.degree. behind one sinusoidal voltage, and a phase sensitive detector 29 arranged to vary the frequency of the oscillator 10 to maintain a constant phase difference.

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: An inverter-motor combination is regulated in accordance with this invention to minimize deterioration of the power factor as the inverter is reduced from 100% load. This is accomplished by sensing the motor current and providing a control signal to regulate the inverter output frequency in accordance with a first function, representing virtually linear decrease in frequency as the load is reduced from 100% to substantially 70% of full load. A constant voltage stage is connected to regulate the d-c bus controller to provide a modified control signal for regulating the d-c bus level according to a second function, maintaining the d-c bus voltage at virtually 100% while the load is reduced to 70%. Thus the d-c bridge is not phased back and the power factor of the complete system is not degraded over this described operating range.

Abstract: A controlled current inverter system forms the basis of an AC motor drive system for furnishing the motor load 18 with a variable frequency, variable magnitude AC current from an inverter 14 which is supplied from a variable DC current source such as a converter 12 by way of a DC link including an inductor 17. Motor speed and torque are controlled through the control of motor current I.sub.M and angle .theta., which is the angle formed between vectors designating motor current and flux through first and second control signal channels 39 and 59 coupled to the DC source 12 and the inverter 14, respectively. A control function of this angle, defined in terms of both method and apparatus, is implemented by means 61 and 63 which limits this angle to predetermined values for relatively low levels of motor current, for example, values of current corresponding to the current required for maintaining a minimum amount of motor flux.

Abstract: The invention relates to a speed control system which includes an inverter circuit for converting a direct current into a polyphase alternating current in the form of a rectangular wave by the switching action of transistors, and an inverter drive circuit adapted to apply control signals to the inverter circuit to bring its output frequency to a desired value, an induction motor being rotated by the alternating current supplied by the inverter circuit. The system features current detection means for detecting current that flows through the output side of the inverter circuit, and decision means for examining the output of the current detection means for a fixed period at a frequency higher than that at which the induction motor is driven.

Abstract: Apparatus and method for high slip operation of an AC electric motor at substantially zero rotation and substantially zero torque in an AC electric motor drive system is disclosed. The electric motor produces a rotation in response to an outgoing signal, such as a drive current, of variable magnitude and frequency supplied by the drive system. An idle control signal is furnished when the drive system is in a substantially zero rotation and substantially zero torque state, where the frequency of the current is approximately zero. The idle control signal causes substantially simultaneously an adjustment of the magnitude of the current to a predetermined magnitude level and a rapid raising of the frequency of the current to a higher frequency value to produce per-unit slip s=(n.sub.1 -n)/n.sub.b greater than 0.1, where n.sub.1 is the synchronous rotation of the stator field of the motor, n is the rotation of the rotor of the motor, and n.sub.b is the synchronous speed of the stator field at motor rated rpm.

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: A fixed gating sequence apparatus and method for an inverter is disclosed. In one aspect of the invention, an outgoing signal of variable frequency is generated by the inverter in response to gating signals provided by an inverter control. The gating signals effectively are provided by a shift register of an inverter control to the gates of the conduction controlled rectifying devices in the inverter in response to a clocking signal. The clocking signal is provided to the clock input of the shift register at a normal system rate when an idle condition (idle control signal) is not present and at a predetermined cycling rate from when the idle condition occurs until a desired fixed gating pattern effectively is provided by the shift register to the inverter. The shift register remains at the stage providing the desired fixed gating pattern until the idle condition no longer is present, whereupon the normal clocking signals are again provided to the shift register.

Abstract: A plurality of arbitrarily loaded induction machines are operated from a single, controlled current inverter by regulating the amplitude of inverter output current in response to the average of the individual induction machine phase angles, the machine phase angle being the phase relationship magnitude between machine air gap flux and current, and by regulating the frequency of inverter output current in response to the average of the individual induction machine phase angle and the slip frequency of the most heavily loaded induction machine. The most heavily loaded induction machine is thus assured of having sufficient flux, thereby greatly reducing the possibility of machine pull-out and resultant inverter instability.