Abstract: A reduced voltage starter for gradually starting a polyphase motor having an acceleration control circuit for gradually applying power to the motor and detector circuits for detecting various fault conditions for terminating power to the motor. A shorted solid state switch detector senses when one of the semiconductor switches applying power to the motor is shorted to terminate the application of power from the remaining phases. A phase angle control circuit insures a uniform application of power to the motor. A phase rotation detection circuit detects when the three phases are in other than their correct sequence and terminates power in the event of such detection. An underload detection circuit senses when the current drops beneath a preselected reference after the motor has reached its full speed and terminates power in response to such detection. A line-to-line to line-to-neutral convertor produces signals representative of the line-to-neutral voltages which are necessary for other circuit functions.

Abstract: A slip frequency type vector control apparatus for an induction machine which is provided with first and second feedback circuits for correcting respective magnetization current command and torque current command supplied feed-forwardly so as to eliminate the influence of a change in temperature of the induction machine secondary resistance and realize a correct vector control.

Abstract: The invention relates to a method for simulating the actual load angle value (.nu.) of polyphase machine from the terminal voltages (u.sub.R, u.sub.S) and conductor currents i.sub.R, i.sub.S) of at least two phases (R, S) of the stator of a polyphase machine, each of which represents stator-oriented a-c variables, where said stator-oriented a-c variables (u.sub.R, u.sub.S, i.sub.R, i.sub.S) are transformed into a first stator current component (i.sub.1) and a second stator current component (i.sub.2) of the machine current vector (i.sup.s) and an absolute value of the machine flux vector (.vertline..phi..sup.s .vertline.), each of which are field-oriented d-c variables. According to the invention, a first corrected stator current component (i.sub.1) consisting of a stationary component (i.sub.1s) and a dynamic component (i.sub.1d) is generated where the stationary component (i.sub.1s) is determined form the absolute value of the machine flux vector (.vertline..phi..sup.s .vertline.

Abstract: An electric motor running system consists of a photovoltaic array, an inverter for inverting output voltage of the photovoltaic array to AC voltage and automatically controlled so that the frequency is changed in accordance with the output voltage of the photovoltaic array, maintaining the ratio of the voltage to the frequency at a constant value, an induction motor operated by application of the AC voltage from the inverter, and a frequency increasing circuit for increasing the output frequency of the inverter instantaneously so that the motor produces the torque larger than the load starting torque when the motor is started and further decreasing the increased output frequency of the inverter to the normal running frequency after the increased output frequency is maintained for a predetermined period of time. This construction allows the motor to be smoothly started even where a load connected to the motor is a positive displacement pump which has a large static friction torque.

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

Abstract: A method for the formation of the actual load angle value for a field-oriented regulated rotary field machine and apparatus for field-oriented regulation of the machine. In order to impress in a voltage-impressing converter the load angle, i.e. the angle between field axis and stator current vector, an angle regulator is used to which a given nominal load angle value (wif*) is supplied. In order to form from the stator-oriented acutal current angle (wis) tapped off at the machine via a current detector (I-DET) the actual load angle value associated the nominal load angle value with wif*, by a decoupling computing unit (CAL) from the given components of the field-oriented nominal current vector, the field-oriented angle (wuf*) of the associated field-oriented nominal voltage vector is calculated and subtracted from the stator-oriented angle (wus) of the actual voltage vector. The actual load angle value (wif) is then given by wis-wus+wuf*.

Abstract: The present invention relates to method and apparatus for asyncyhronous motor's speed regulation using strobe control, which may be carried out graded or nongraded speed regulation in conventional monospeed squirrel cage motor with simplicity, reliability, cheapness and high efficiency. It provides a notable electricity-saving result with good economical efficiency, especially in asynchronous motors speed regulation of ventillator and water pump driving. The said speed regulation method is using switch 5,6 sequentially to transmit a positive half-wave voltage and a negative half-wave voltage between the input terminals of strating and working windings of asynchronous motor 1, and then, will be repeated above said cycle continuously.

Abstract: In the operation of an A.C. motor by switching the number of poles of the motor or the power sources of different frequencies, switching operating circuit is constructed to automatically switch so that the motor does not overheat by the above-described switching. Thus, the energy of the power sources can be saved.

Abstract: A motor control circuit for operating a permanent split capacitor motor from an ac source. The motor control circuit causes the motor to accelerate and decelerate according to a velocity profile. A driver circuit connects the motor to the ac source. The driver circuit receives a pulse signal at a predetermined time point after a zero crossing of the ac source and connects the ac line current to the motor at the predetermined time point, then the driver circuit disconnects the ac source from the motor at the next zero crossing of the ac source. A ramp wave signal is generated, each ramp thereof beginning at a zero crossing of the ac source and a dc voltage representative of the speed of the motor is also generated. A velocity profile having a predetermined period is provided on an output of a velocity profile generator. A first comparator circuit has a first input for receiving the dc voltage and a second input for receiving the velocity profile. An error signal is provided on an output thereof.

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

Abstract: A power system stabilizer (PSS) to bring the constant in a phase lead-lag circuit of the PSS to an optimum value by having such procedures carried out in its phase lead-lag compensation circuit as to apply the ruler to lead the phase of the PSS when the period of the power fluctuation in each mode tends to decrease and to lag the phase of the PSS when conversely the period tends to increase by means of a fuzzy inference device to detect results of the periods weighted by the degrees of the tendency, to superpose the outputs obtained by application of the rule to obtain the center of gravity, and therewith finally to vary the constant in the amplification and phase lead-lag circuit of the PSS.

Abstract: The present invention relates to a motor control apparatus having a discharge circuit 7 for reducing a voltage which is regenerated from motor 5 to the driving circuit 4 in the braking of an AC servomotor or the like, a protection circuit 8 for protecting the discharge circuit 7, and a voltage-drop detection circuit 20 for making the driving circuit stop after an activation of the protection circuit 8. The motor control apparatus contains a detection circuit 16, which detects a voltage of the smoothing capacitor 3 which is connected to the input terminal of the driving circuit 4 via the protection circuit 8 which is connected in series to the discharge circuit 7, and a voltage-drop detection circuit 20 which stops the driving circuit 4 after activation of the protection circuit 8.

Abstract: A flat frequency, constant voltage power source device is provided for parallel operation of a plurality of electric generators. The generators include exciting windings of induction motors integral with the generators for connecting and disconnecting outputs of the generators. A starting sequence of the electric generators is based on a start signal provided externally and start preparation completion signals indicating completion of start preparation routines. The induction motors of the generators are thereby varied in frequency so that the generators can be synchronized in phase for their effective parallel operation.

Abstract: An induction motor torque/flux control system the motor flux is forced down while accelerating and force up while decelerating to maintain a required flux level at all speeds. This is achieved through vector control by generating a direct current component in relation to the flux demand while imposing limits thereto corresponding to the maximum desirable resultant current vector, and by generating a quadrature current component which is held between limits defined by the sum of the squares of the two current components. The three-phase currents of the motor generated by vector control transformation are used to control a voltage-source inverter in a bang-bang fashion. The conventional bang-bang technique is improved by typing up one pole while controlling in the bang-bang mode the two other poles. To this effect the motor back emf is detected when the poles are simultaneously tied to one of the DC link terminals, and the tied-up pole is selected by the emf so detected.

Abstract: A device for controlling an AC motor for a fork lift truck comprises a detector to detect direction of rotation of an AC motor. The direction of rotation thus detected is compared with a desired direction of rotation of the AC motor, and the AC motor is controlled such that the AC motor operates in a power running mode when the actual direction of rotation of the AC motor is equal to the desired direction of rotation of the AC motor, but it operates in regenerative braking mode when said actual direction of rotation of the AC motor fails to be equal to the desired direction of rotation of the AC motor. The desired direction of rotation of the AC motor may be set manually by an operator or a driver of a vehicle drien by the AC motor.

Abstract: A method for controlling an AC induction motor in such a manner that the same degree of control as can be exerted on a DC motor is effected without requiring the use of a flux sensor or coordinate transformations. With reference to an asymmetrical-T type equivalent circuit of the AC induction motor, the input current or voltage to the stator coils of the motor is controlled so that an exciting current has a constant amplitude and continuous phase upon an abrupt change in an input torque instruction. It is demonstrated that this method produces essentially the same control as for a DC motor while methods based upon other equivalent circuits do not.

Abstract: A circuit and method to improve power efficiency of AC induction motors is described for adopting an AC PWM chopper method in power input controls. For a period of several seconds after initially supplying power source voltage, the starting voltage is bypassed by a relay switch to prevent malfunctioning of devices.A PWM waveform is provided by a microcomputer and it is combined with a zero crossing signal of the power source voltage. The combined signal is controlled and buffered by photo couplers, by which power source voltage is controlled with transistors of a power controller unit.A current flow through the motor is detected and store into memory of the microcomputer. In a next sequence, another PWM waveform is provided to again detect other current flow through the motor and its detected value is compared with the previous value store in the memory. These sequences are repeated to search for a minimum current value according to variation of loading on the motor.

Abstract: An improved induction motor control system. Single-phase and three-phase AC induction motors are controlled in accordance with the equation y=m=x+b, where y is the phase angle, m is the slop, x is the firing delay and b is the offset. Subsequently, the firing delay is increased by predetermined amounts, the behavior of the phase angle is evaluated for several cycles, and the motor is controlled based on the results of the evaluation, thereby minimizing energy consumption.

Abstract: An improved regulator mechanism for a single-phase or three-phase, two-speed motor is disclosed. The regulator mechanism includes a first energizable contactor (having at least one contact) and a second energizable contactor (having five contacts) which cooperate to cycle the motor between inoperative and operative states and to configure the motor windings and power lines so as to provide first and second speed operation.

Abstract: A three-phase electric motor is coupled to each phase line of an electric source by pairs of SCR's coupled in inverse parallel relationship. One of the SCR's in each pair is triggered by a signal from a conventional motor control circuit which regulates the phase angle at which the SCR turns on. The other SCR in each pair is an optically triggered device which is activated by light emitted from an LED in one of the legs of a three-phase rectifier bridge in the control circuit power supply. When the LED within a leg of the power supply is forward biased so as to conduct current, it emits light which triggers a correspondingly biased opto-SCR to supply current to the motor. A separate transistor is connected in parallel across each of the LED's to provide a current shunt path when the motor is to be turned off so that the LED does not emit light and trigger the SCR.