Abstract: A field-oriented controller for a 3 phase induction motor is powered by a dc power source through a static inverter. Current reference signals are compared with current feedback to produce error signals. They are amplified by a proportional plus integral amplifier, whose output goes to a threshold comparator having negligible hysteresis. Flip-flops, through which the threshold comparators' gating signal outputs are fed, are clocked at a fixed frequency to introduce pseudo-randomness into the gating times. This reduces apparent acoustic noise of the motor. Asymmetrical anti-overlap delays for the gating signals are made long enough to serve also as the principal means for limiting the maximum frequency of gating. Locking circuitry overrides the proportional integral error signal in one phase at a time, and holds the inverter's gating in one switching state throughout the approximate middle 60.degree. interval of each phase. During each such 60.degree.

Abstract: An induction motor control method includes producing a primary current as a current command which takes all constants of an induction motor (d) into consideration. An output torque is obtained which is linear with respect to a torque command (Tm), a voltage at a DC link portion is detected, and an excitation flux command is varied by this DC voltage (V). This enables constant-output control to be performed irrespective of fluctuations in power supply voltage. Further, a power-factor adjusting circuit (q) is provided for adjusting the phase between voltage on the AC power supply side and current at the time of regenerative braking, so that reactive power is reduced.

Abstract: A control circuit for a closed loop command system having an output which is adjusted to conform with an input command level. A pulse generator provides digital pulses with durations representative of the output of the system. Command pulses are generated by the system pulses and have durations representative of the input command. Each pulse is applied to logic gating along with the complement of the other pulse, with the logic gating providing a signal indicating whether the system pulse or the command pulse is longer. The last gate signal is retained in a flip flop memory and is used to adjust the output power level up or down depending upon the result of the pulse length comparison.

Abstract: Power consumed by an ordinary a.c. induction motor is reduced by having two parallel sets of separately excited RUN windings. When the motor is lightly loaded, a.c. power feeds only one of the two RUN windings, thereby reducing the flux density in the motor stator and as a result reducing eddy current losses and copper losses. Whe the load increases, a.c. power is immediately fed to the other RUN winding thereby increasing the magnetic flux density and the motor power. The a.c. power fed to the second winding is variably controlled by a thyristor, and the amount of thyristor coupled power may be determined from sensing changes in the speed slip of the induction motor wrought by load changes. Through having the one RUN winding permanently connected with the power source, while the other RUN winding power is modulated by the phawe controlled gating action of the thyristor, less a.c.

Abstract: An induction motor drive having source and load side converters with individual control channels for the respective converters includes a cross tie arrangement between the channels for increased system stability.

Abstract: A frequency converter is provided for the power supply of an asychronous motor, comprising:a rectifier bridge (11) connected to a multiphase network and to an intermediate DC circuit (12);an inverter (13) comprising three pairs of static switches (T1-T6) connected in a Graetz bridge; characterized by;a means (21) for reading the current associated with the intermediate circuit (12) and elaborating an image signal of the reverse circuit and delivering an image signal of the current in this circuit;a stabilization control circuit (22) connected to said means (21) and delivering a reverse current excess signal (ST) when the signal (I.sub.d) exceeds an adjustable threshold; anda means (25) for reducing the output voltages of the inverter, and adapted for modifying the modulated pulses, this means being controlled by the output signal (ST) of the stabilization control circuit (22).

Abstract: A start circuit for a single phase AC induction motor employs an impedance in series with the run winding to develop a voltage drop proportional to the current through the run winding, and a pair of LEDs or another light emitting device across this impedance to produce a light output whose intensity varies with the field current, and hence in a generally inverse relation with motor speed. A solid-state AC current switch, which can be a triac or a pair of back-to-back SCRs, is gated by a photosensitive circuit that includes a photosensitive element. A light conduit, which can be a light pipe or light dome, for example, carries the light output from the light emitting element to the photosensitive element. The device of this circuit is highly reliable, has no mechanical contacts, and is relatively insensitive to temperature and voltage fluctuation.

Abstract: The acceleration/deceleration control apparatus using slip speed detects an angular frequency .omega.r corresponding to an execution speed of an induction motor and derives an angular frequency .omega.s corresponding to a slip speed corresponding to a slip speed in response to a torque of the said motor, from a vector controller of the said motor.On the other hand, an allowable value .omega.s' of said angular frequency corresponding to the said .omega.r is prepared beforehand, and is compared with said angular frequency .omega.s.According to the result of this comparison, the IM rotation is controlled. So even if the induction motor is used as servo motor, no shock of the torque will flow through the motor and the motor itself will not be stalled.

Abstract: An induction motor control apparatus includes a detector, a memory, a correction current generator, and a primary current correction circuit. The detector detects a rotational position of a rotary magnetic flux generated by a multi-phase primary current applied to a primary winding of an induction motor. The memory stores correction values corresponding to measured values of torque ripples periodically generated in correspondence with the rotational positions of the magnetic flux, receives an output from the detector for detecting the rotational position of the magnetic flux, and outputs one of the correction values stored in the memory in correspondence with the rotational position. The correction current generator generates a correction current by the correction value read out from the memory in correspondence with the rotational position of the magnetic flux. The primary current correction circuit corrects the primary current by the correction current.

Abstract: The invention relates to a device for improving the stability of rotation of the rotor of a single-phase synchronous motor mounted in an apparatus housing. The motor exhibits an average motor torque on which strong alternating torques are superimposed and which drives a preferably rotating load. The rotating load may be a small domestic appliance such as a citrus-juice extractor, a knife sharpener, or a dry-shaver with rotatary cutters.

Abstract: A generator/motor system comprises a generator/motor having a primary winding and a secondary winding installed on the motor rotor coupled to a prime mover/load, a main circuit interposed between a power system and the primary winding of the generator/motor, an excitation circuit including a frequency converter inserted between a part of the main circuit and the secondary winding of the generator/motor, a frequency difference detector for determining the difference between the frequency of the power system and a frequency dependent on the rotational speed of the load, and a phase-shift control device for controlling the firing phase of the frequency converter in the excitation circuit by use of a signal from the frequency difference detector as a reference signal.

Abstract: There is disclosed a protecting apparatus for a secondary excitation type variable speed AC generator/motor having a primary winding connected to an electric power system and a secondary winding each phase of which is AC excited by an independent power converter unit. The protecting apparatus is arranged to detect an electrical event which includes at least one of an overvoltage and overcurrent appearing at each phase of the secondary winding of the AC generator/motor, to decide whether the detected electrical event meets a predetermined condition and to close, when the electrical event detected in respect to any of phases of the secondary winding is decided as meeting the predetermined condition, a switch circuit connected in the corresponding phase of the secondary winding.

Abstract: A capacitive breaking circuit for a single phase induction motor using a double throw power switch which in the off position, connects a series string, consisting of a charging rectifier diode, a current limiting resistor, a centrifugal switch and a braking capacitor, to the two power input terminals of a small single phase induction motor. With this circuit, while the motor is running, when the power switch of the motor is turned ON, DC current also charges the braking capacitor. When the power switch of the motor is turned to OFF, the braking capacitor discharges through the motor winding via the power switch to produce the braking function.

Abstract: A control device monitors the elapsed off time of an oil filled deep sea electric motor 4, and compares this with a calculated time for the oil temperature to drop to a predetermined value at a sensed water depth. When the two times are equal a low, heating current is supplied to the primary winding 11 to prevent the oil from becoming more viscous. The heating current is insufficient to rotate the motor armature, and its intensity is increased with depth corresponding to the decrease of the water temperature with depth.

Abstract: Disclosed is a control apparatus for a brush-less motor, which can prevent commutation failure of an inverter for driving the motor. The control apparatus, according to the invention detects a counter EMF of the motor, and the detected counter EMF is applied to a PLL circuit. In the course of normal operation of the motor, an output of the PLL circuit is used for controlling the advanced control angle of a motor drive inverter. Any abnormality in the condition of the motor, such as that arising from an abrupt change in load of the motor, causes a sudden and substantial variation in the magnitude and phase of the counter EMF. Since the internal condition of the PLL circuit changes in response to this counter EMF variation, a signal generated by the PLL circuit is therefore used to detect the counter EMF variation.

Abstract: A vector control system for an induction motor driven by a power converter which generates three phase ac currents containing harmonics.

Abstract: A hermetic box contains a motor and a self reset type protector which interrupts the supply of electric power to the motor when an abnormally heated condition takes place in the hermetic box and automatically supplies again the electric power when the abnormally heated condition ceases. The motor is energized by an inverter having AC output terminals connected to the motor outside of the hermetic box. A current detector which detects that no current is flowing into the motor is provided on the output side of the inverter outside for a hermetic box.

Abstract: Electric power consumed by an a.c. induction motor is measured and sensed changes in power factor are used to modulate the combined magnetic flux produced in the motor field by two sets of RUN windings. A main RUN winding set, which normally couples fully with the a.c. power, is engineered to have sufficient ampere-turns to produce just enough magnetic flux to operate the motor with a light load and maintain a moderately high power factor. Motor driven load increases are determined by sensing a corresponding increase in the power factor of the main RUN winding set, whereupon power flow to a secondary RUN winding is proportionately increased. Considerable energy savings occurs when the motor drives a fluctuating load due to reduced magnetic field excitation under all but full load conditions, with the result that energy ordinarily wasted by eddy currents, copper losses, and poor power factor operation is considerably lessened. Other possible losses due to harmonic distortion of the a.c.

Abstract: A circuit is described for controlling the speed of an A.C. motor driving a cooling fan in response to the temperature at a point being cooled in which a temperature responsive impedance is used to control the current in an impedance of the output circuit of an amplifier that is connected in series or parallel with the windings of the motor.

Abstract: A start circuit for an induction motor having a main winding and a start winding includes a sensor of main-winding current. A detector detects the level of main-winding current sensed by the sensor. The start circuit includes a reference generator driven by the level detector and providing a reference level proportional to an average value of main-winding current. The reference level can vary slowly in accordance with a long-term drift in magnitude of the main-winding current. A switch energizes and deenergizes the start winding in accordance with relative values of a signal of the detector and the reference level, thereby allowing for automatic restarting in the event of a sudden increase of current due to a motor stall.