Abstract: A control circuit, processor and half-bridge are provided for operating electric motors. The half-bridge includes a first electronic switch lying between a supply voltage and a phase tap, and a second electronic switch lying between the phase tap and ground. The control circuit is adapted to control the first and second electronic switches with one out of only three switching signal pairings. The signal pairings consist of (i) the first switch being on and the second switch being off, (ii) the first switch being off and the second switch being on, and (iii) the first and second switches being off The processor has a signal output port coupled to control the control circuit to select one of the three signal pairings, via one of three possible output signals at the signal output port.

Abstract: An inverter control device for driving a motor with small size, light weight and low cost is provided. The inverter control device generates PN voltage correction coefficient by dividing the reference DC voltage by the detected DC voltage, and corrects the voltage command of each phase by multiplying the voltage command of each phase obtained by the motor voltage command generator with the PN voltage correction coefficient output from the PN voltage corrector, thus resulting in the corrected motor voltage command. The inverter control device has, in generating PN voltage correction coefficient, a first mode in which the PN voltage correction coefficient is set to 1 when the DC voltage value is more than the reference DC voltage, and a second mode in which the value obtained by dividing the reference DC voltage by the detected DC voltage is set to the PN voltage correction coefficient.

Abstract: The motor driver having a plurality of output circuits each having two switching elements connected in series includes: a phase switch circuit for putting a switching element on one side of one output circuit among the plurality of output circuits in the ON state during a time period corresponding to a predetermined electrical angle, and performing switching operation for switching elements on the other side of plural output circuits among the remaining output circuits; and a conduction period control section. The conduction period control section generates a signal for controlling the switching operation. Specifically, when the number of times of switching operation performed during the time period corresponding to the predetermined electrical angle is equal to or less than a predetermined value, a switching element corresponding to a phase, for which the magnitude of the current should be decreased, is turned OFF in the time period corresponding to the next predetermined electrical angle.

Abstract: An apparatus monitors performance of a power inverter to detect malfunctions. A first signal indicates the direction that electric current exists between a first voltage bus and an output terminal of the power inverter. A second signal indicates the direction that electric current exists between a second voltage bus and the output terminal. A third signal indicates the direction that electric current occurs between the output terminal and a load. Other signals designate a commanded conductivity of switches that control the current within the power inverter. A controller analyzes the values of those signals to determine whether a malfunction has occurred.

Abstract: In a synchronous motor control device that corrects a deviation in rotational position which is related to a rotational position detector for a synchronous motor on which vector-control is performed, the synchronous motor control device includes: a current instruction generator that disables a torque instruction to set d-axis and q-axis current instructions as zero when a phase correction instruction is inputted; a current controller that outputs d-axis and q-axis voltage instructions based on the d-axis and q-axis current instructions; a phase correction quantity detector for determining the amount of offset in which the d-axis voltage instruction becomes zero when the phase correction instruction is inputted and the d-axis voltage instruction is not zero; an adder for adding a rotor positional angle and the amount of offset; and a voltage converter for determining three-phase voltage instructions based on the additional value, the d-axis and q-axis voltage instructions.

Abstract: An inverter controller for driving a motor includes a rectifier having a reactor, an inverter, a capacitor, a generator which generates a voltage command value for each phase of the motor, a detector which detects a DC voltage between the DC buses of the inverter, a first corrector which calculates a voltage correction coefficient by comparing the DC voltage with a predetermined DC reference voltage, a second corrector which corrects the voltage command value by multiplying the voltage command value and the voltage correction coefficient, a selector which selects either two-phase modulation or three-phase modulation as a modulation type, a computer that computes a carrier frequency, and a pulse width modulation controller which controls a pulse width modulation so that a value of a voltage to be applied to the motor equals to the corrected voltage command value, by using the selected modulation type and the selected carrier frequency.

Abstract: A speed control circuit for a dc brushless motor includes a switch circuit and a voltage-detection circuit. The voltage-detection circuit is actuated depending upon high or low voltage of power supply to thereby cause the switch circuit to output high or low operating voltage to a driver circuit of the motor in response to changes of the voltage of the power supply. The motor is adjusted and operated at desired speeds by a rated range of input voltages according to the high or low operating voltage.

Abstract: A current detection method for an electric motor which detects phase currents of the electric motor driven by a power converter that provides ON/OFF control of bridge-connected switching elements, based on a pulse-width modulation excitation pattern, to convert a direct current into poly-phase alternating currents. The method includes connecting a current detecting element which produces a signal corresponding to a current value at the direct current side of the power converter and changing the pulse-width modulation excitation pattern by executing a shift of time of any of the phases of the pulse-width modulation excitation pattern so that a signal directly or indirectly corresponding to the phase currents is produced at the current detecting element. The method also includes detecting the phase currents of the electric motor based on the signal produced at the current detecting element and the excitation pattern which has been changed.

Abstract: A synchronous motor controlling apparatus which can be applied to the carrier synchronized position estimating method as well and have protection-related functions such as detection of inverted magnetic pole position of a motor in a simple method, and an electric motor using the synchronous motor control apparatus. A controller controls a voltage applied to an AC motor with a PWM signal. A magnetic pole position detector of the controller detects a current of the AC motor to estimate a pole position of the AC motor. A fault detector detects a fault in the estimated magnetic position of the AC motor.

Abstract: An inverter control apparatus and method of a three-phase motor includes disposing three maximum phase voltage vectors each having an equivalent angle interval corresponding to maximum values of each phase voltage; setting maximum phase voltage vector regions by predetermined angles with respect to each of the maximum phase voltage vectors; setting minimum phase voltage vectors corresponding to the maximum phase voltage vectors in between the maximum phase voltage vector regions; obtaining a desirable voltage by turning on a first switch and turning off a second switch, both connected to the phase terminal of a corresponding maximum phase voltage in each maximum phase voltage vector region; and changing a duty ratio of control signals with respect to other two switches corresponding to the other two phase voltages.

Abstract: A motor abnormality detection apparatus is capable of performing the abnormality detection of a motor (5) without supplying a special electric current thereto for abnormality detection in an ordinary control state. A motor control device (100) controls the motor (5) through vector control which is described by a two-phase rotating magnetic flux coordinate system having the direction of a field current as a d-axis direction and a direction orthogonal to the d-axis direction as a q-axis direction. A motor abnormality detection part (100h) (100h) performs an abnormality determination of the motor based on target impression voltages (Vd*, Vq*) impressed on the motor (5).

Abstract: A motor controller is provided including a synchronous motor, a feed back detector for detecting the position and velocity of the rotor of the synchronous motor, a detector for detecting a magnetic pole position of the rotor of the synchronous motor, an inverter for controlling an electric power to be supplied to the synchronous motor, an estimator for estimating the magnetic pole position of the rotor of the synchronous motor, and a detector for detecting the abnormality of the feed back detector.

Abstract: A limiting circuit for a brushless dc motor in accordance with the present invention comprises a first transistor, a second transistor, a first resistor and a second resistor. The first transistor, the second transistor, the first resistor and the second resistor are arranged in complementary connection to constitute the limiting circuit which has a first terminal connected to a power source and a second terminal connected to a motor drive circuit.

Abstract: Systems and methods for controlling an induction motor including detecting a field weakening operation state of the motor, wherein the field weakening operation state is detected when a flux current, Id, in the motor is reduced to a predetermined fraction of its normal, non-voltage limited value. The systems and methods also including an overmodulation operation state of the motor before said field weakening operation state is detected and enabling the overmodulation operation state of the motor after said field weakening operation state is detected.

Abstract: A motor speed control circuit includes a switch circuit and a voltage-detection circuit. The voltage-detection circuit is actuated depending upon high or low voltage of a power supply to thereby cause the switch circuit to output high or low operating voltage to a driver circuit of the motor in response to changes of the voltage of the power supply. The motor is adjusted and operated at desired speeds by a rated range of input voltages according to the high or low operating voltage.

Abstract: In a rotor assembly having a rotor supported for rotation by magnetic bearings, a processor controlled by software or firmware controls the generation of force vectors that position the rotor relative to its bearings in a “bounce” mode in which the rotor axis is displaced from the principal axis defined between the bearings and a “tilt” mode in which the rotor axis is tilted or inclined relative to the principal axis. Waveform driven perturbations are introduced to generate force vectors that excite the rotor in either the “bounce” or “tilt” modes.

Abstract: A system for controlling a regulator equipped with an electric servomotor in a motor vehicle. With reference to an example of an electronic steering system that has an electric-motor steering regulator, output parameters are generated by a model-assisted monitor for evaluating the suitability of a correction for the regulator, and thus criteria for a possible shutdown or to initiate emergency action, as a function of setpoint parameters for the electric servomotor, of instantaneous parameters measured by individual sensors, and of the driving state, and, based on a setpoint behavior of the regulator and on a model simulating the control sections it contains.

Abstract: A system and methodology for control of a switched reluctance electric machine comprising: a switched reluctance electric machine including a sensor generating and transmitting a sensor signal indicative of an operating characteristic; a controller operatively coupled to the switched reluctance motor and the sensor; and the controller executing a method.

Abstract: A method of regulating the power demanded by a rail motor including a current collector system cooperating with a catenary supplied with direct current power by power supply substations distributed along the track includes the steps of: measuring the catenary voltage Vcat at the rail motor, measuring the catenary current Icat at the rail motor, evaluating the no-load voltage Vcat0 of the substation supplying power to the catenary to which the rail motor is connected, evaluating the maximum power available to the catenary from the equation: P ⁢   ⁢ max = ( Vcat 0 ) 2 4 * R where R is the resistance of the catenary, and limiting the power demanded by the rail motor to a power limit Plim less than or equal to the calculated maximum power Pmax.

Abstract: A motor control system includes a control section that performs operating range limiting processing in which a junction temperature of switching element of an electric power converter is calculated and compared with a preset temperature limit, and when the junction temperature exceeds the temperature limit, junction temperature reduction processing is performed to make the junction temperature equal to or less than the temperature limit, whereby the switching elements can effectively used to their maximum temperature limit irrespective of a temperature detected by a temperature sensor, thus expanding the operating range of a motor.

Abstract: A three-phase motor protector uses two toroids to monitor all three phases of a three-phase motor. Current and phase loss are monitored directly in phases A and B while the phase C current level is determined by analysis of the phase A and B relationship. Current is induced into the phase A and B toroids from the motor supply lines with the resulting wave fed to an input of high-gain inverting amplifiers to provide A and B square waves which are inputted to separate channels of a microprocessor (U3). The square waves are processed by an AND gate providing an output square wave with a 16.66 percent duty cycle for normal operation. Upon loss of phase C the ANDed result is a digital low since the individual waves of phases A and B become an inverse of one another. In order to prevent nuisance tripping an AND output of less than 2 percent duty cycle is treated as a phase loss.

Abstract: System and method for enhancing the torque output of a field oriented induction motor including a controller having a plurality of predetermined control parameters operable for processing input signals to generate output signals. The plurality of predetermined control parameters are dependent upon the nature of the input signals and the operational state of the motor. A sensor system is operable for communicating feedback signals related to the output signals and the operational state of the motor from the motor to the controller.

Abstract: A fan motor speed control system for controlling the fan motor speed of an air conditioning system includes a power output circuit including a power triac which is turned on and off by an opto-isolator connected to a pulse generator circuit for varying an AC voltage waveform imposed on the fan motor. The pulse generator circuit is connected to heating and cooling ramp circuits and a minimum speed circuit to provide a variable voltage signal imposed on the pulse generator circuit corresponding to the temperature difference sensed by a return air sensor and a heating or cooling sensor or by separate heating and cooling sensors disposed adjacent respective heating and cooling heat exchangers of the air conditioning system. An adjustable minimum speed circuit and a cutoff circuit are provided to control motor minimum speed or motor shutoff when a predetermined minimum speed is reached to prevent motor bearing failure or overheating.

Abstract: The present invention relates to a method and an apparatus for controlling an electric motor by regulating at least the current Iout, the voltage Uout and the frequency fout to an input of said motor, where the number of revolutions of said electric motor is proportional to said frequency fout. If an available power Pin from an energy source is greater than or equal to the nominal requested power Pnom of said electric motor, the current Iout, voltage Uout and frequency fout are set to there corresponding nominal values Inom, Unom and fnom, respectively, to achieve said requested power Pnom and frequency fnom. If said available power Pin is less than the requester power Pnom, the voltage Uout and the frequency fout are reduced such that the relation between the voltage Uout and the frequency fout is essentially constant while said current Iout is kept at its nominal value Inom.

Abstract: An electrical steering system for a vehicle includes an electrically supplied steering motor arrangement which is connected with an inverter arrangement, whose output voltage is influenced by a computer arrangement, and a sensor arrangement. To reduce the cost of the steering system while also allowing the steering system to be steerable during braking in the case of a fault, the steering motor arrangement has a redundant steering motor which is connected with the computer arrangement via two separately run control circuits. The control circuits have separate electric supplies and the computer arrangement is redundant.

Abstract: An electric power steering system is provided which assists a steering operation by applying a driving force generated by an electric motor to a steering mechanism of a motor vehicle. The system includes a sensor (e.g., a torque sensor) for acquiring information necessary for controlling the electric motor, and a board provided adjacent the electric motor and having a sensor signal processing circuit for processing a signal from the sensor. A temperature sensor for acquiring temperature information necessary for controlling the electric motor is mounted on the board.

Abstract: A forced air heating and/or cooling system utilizing an induction type fan motor is controlled by a controller circuit which is operable to continuously vary the speed of the fan motor during a start-up phase and a shut-down phase of the heating and/or cooling cycle. The controller circuit includes terminals for connection to the source of electrical energy for the heating and/or cooling system and for connection to the system controls without altering the control function or circuitry thereof. The controller circuit includes temperature sensors which are operable to control start-up and shutdown of the fan motor over continuously variable speed operating cycles in response to sensed temperature of the air being circulated by the fan.

Abstract: This invention relates to a system for limitation of the output current from a speed controller for three-phase asynchronous electric motors, comprising a PWM type converter in which the electronic switches are controlled by a microcontroller circuit (Mc), characterized by the fact that the microcontroller circuit comprises means (LIC) of calculating the modulus of the current vector using motor phase current measurements, and comparing it with a limitation set value in order to obtain a limitation error (y) and to calculate a correction voltage (&Dgr;V) that is added to the control voltage (V) applied to the motor.

Abstract: A motor driver having output circuits each including upper and lower side switching elements connected in series. The motor driver includes: a current detection resistance connected in series with the output circuits in common; a phase switch circuit for turning ON a switching element on one side of one of the output circuits for a time period corresponding to a predetermined electrical angle and switching switching elements on the other side of a plurality of output circuits among the remaining ones of the output circuits; and an ON-period control section for generating a signal for controlling the switching operation so that each of periods obtained by dividing the time period includes a first period in which a plurality of switching elements are turned ON and a second period in which one of the switching elements turned ON in the first period is kept ON.

Abstract: The invention relates to a motor control circuit for a computer system fan motor, comprising a temperature sensor, a sensor amplifier, a fan command for applying a voltage to the fan motor according to the output of the sensor amplifier, and feedback control means. The circuit of claim also comprises means for stopping the supply of voltage across the fan motor terminals, irrespective of the output of the temperature measuring means. The sensor amplifier allows easy setting of the parameters of the voltage according to the temperature measured by the temperature sensor.

Abstract: An adjustment device for adjusting an article of furniture, includes a drive unit having at least one direct current positioning motor connected to a mains power source; a control unit with at least one switching device for actuating the positioning motor(s); and a mains disconnect relay connected to a mains power plug assembly or a supply line connecting the voltage source to the mains. An additional switching unit which is separate from the switching device(s) for actuating the positioning motor(s) is provided for actuating the mains disconnect relay.

Abstract: Method and system for controlling an induction machine are provided. The method allows to sense rotor position of the induction machine using a relatively low-resolution rotor position sensor configured to supply a stream of pulses indicative of angular increments as the rotor position changes. A memory device is used for storing a synchronous angle boost function. The method further allows to retrieve from the memory device at least one function parameter for providing a synchronous angle boost during a start up mode of operation of the induction machine. Upon sensing a predetermined number of pulses from the rotor position sensor, the method allows to switch from the start up mode of operation to a normal mode of operation, wherein the boost provided to the synchronous angle is discontinued upon switching to the normal mode of operation.

Abstract: In a control circuit for a power converting apparatus, such as a three-phase inverter, unnecessary switching operations of switching elements are avoided.

Abstract: A system and a method of vector sensorless control for electrical drives with induction motors, based on the generation of a high frequency rotating magnetic field which, by composing with the main magnetic field, produces a change of the saturation level as a function of the relative positions taken during the motion. Variation of the saturation level produces a modulation of the zero sequence component of the stator voltage, which is used to evaluate the position of the main field.

Abstract: A back EMF monopole motor and method using a rotor containing magnets all of the same polarity and in a monopole condition when in momentary apposition with a magnetized pole piece of a stator having the same polarity, said stator comprised of a coil with three windings: a power-coil winding, a trigger-coil winding, and a recovery-coil winding. The back EMF energy is rectified using a high voltage bridge, which transfers the back EMF energy to a high voltage capacitor for storage in a recovery battery. The stored energy can then be discharged across the recovery battery through the means of a contact rotor switch for further storage.

Abstract: A method monitors an operational condition of an electric motor, and stores in a memory device general trend, prognostic, diagnostic, and hazardous event information indicative of the motor's operational condition. The method includes the steps of sensing characteristics indicative of the operational condition of the electric motor, such as vibration, temperature, magnetic flux, and the voltages applied to the motor's windings, and generating sensor signals related to the sensed characteristics. Upon the occurrence of a first circumstance, such when measurements of the motor's speed, winding temperature, and voltage, indicate that the motor is operating within its normal load profile, prognostic information is extracted from the sensor signals. The prognostic information provides a profile of the motor's operational condition over time without the influences of fluctuating loads, temperature, and voltage.

Abstract: A variable speed power tool may include a speed adjusting device and/or a maximum speed adjusting device for adjusting the operating speed, and a fixed operating speed switch. An operator adjustable speed adjusting device having a position maintaining mechanism also may be utilized. When manipulated by the operator, the fixed operating speed switch gives priority to the adjusted position of the speed adjusting device and adjusts the operating speed to a preset operating speed. In the alternative, a switching device and an internal integrated circuit may be utilized to adjust the operating speed to a target speed using feedback control. The switching device preferably selects a voltage corresponding to the target speed from either a voltage representative of the position of the speed adjusting device or a predetermined voltage representative of the present operating speed.

Abstract: A system (10) for controlling the torque of an induction motor (12) utilizes a flux observer (14). The flux observer (14) receives stator current inputs (16, 18) and a rotor speed estimate (80) and then outputs a rotor flux estimate (20) that provides increased motor control stability at all speeds.

Abstract: A motor controller for an electric power steering system which performs a steering assist operation by applying a torque generated by an electric motor to a steering mechanism. The controller includes: a current command value setting circuit for setting a current command value indicative of an electric current to be applied to the electric motor; a d-q command value setting circuit for setting a d-axis current command value and a q-axis current command value in a d-q coordinate system on the basis of the current command value; and a voltage controlling circuit for controlling a voltage to be applied to the electric motor on the basis of the d-axis current command value and the q-axis current command value.

Abstract: The present invention provides a control system designed for use in either new or existing escalators or moving walkways. The control system is comprised of a main controller and a variable frequency drive. The main controller is attached to the variable frequency drive which controls the speed of the motor based upon various environmental changes, such as passenger load and safety conditions. The control system of the present invention utilizes motions sensors, time relay switches, proximity switches and other electromechanical detectors as intelligence to detect faults and to control and vary the speed of the motor through the variable frequency drive.

Abstract: A method and apparatus for controlling the torque of and reducing torque ripple in a permanent magnet motor without using current sensors. By eliminating the need for current sensors, low frequency torque ripple is reduced. A voltage mode control method is implemented to control the motor. In response to the position and speed of the rotor and a torque command signal, a controller develops motor voltage command signals indicative of the voltage required to produce the desired motor torque. A rotor position encoder determines the angular positions of the rotor. From the angular positions of the rotor, a speed measuring circuit determines the speed of the rotor. The position and speed signals are applied to the controller. The controller uses this information and develops the motor voltage command signals indicative of the voltage needed to produce the desired motor torque. An inverter is coupled between a power source and the controller.

Abstract: The temperature (25, 33, 43) of solid state switching devices in variable speed motor drives (11, 18), such as elevator motor drives, are utilized to reduce the load on the drive, by reducing the switching frequency (50) or the commanded load (110). The choice between the preferred non-switching zero state and an alternative zero state is determined (60) by temperature (28, 34, 56) of the switched transistor's anti-parallel diode. The rate of recognizing reduced temperatures is limited (33, 34) to avoid motor speed and/or load variations. The temperature may either be measured (24, 27) or determined (70) from models utilizing manufacturer product specification and normalized thermal transient response from the transistor/diode package to a heat sink.

Abstract: The present invention relates to a control method and a control device for a position sensorless motor which has position sensorless operation and synchronized operation, wherein a rotation position of a rotor is detected on the basis of counter electromotive forces generated in stator coils in the position sensorless operation, the stator coils are excited in synchronization with the detected rotation position of the rotor to rotate the rotor and a deviation between a target position and the present position is determined from a target rotation position according to the position command signal and the detected rotation position, position sensorless close loop drive is made on the basis of the determined deviation, and when the synchronized operation is made, the stator coils of the motor are excited in synchronization with the position command signal to rotate the rotor.

Abstract: A system and method for controlling a switched-reluctance motor, in which a control variable is selected for controlling a figure of merit of the motor. The motor is then operated at a first value of the control variable. The control variable is adjusted to a second value, and the motor is operated at the second value of the control variable. A first indicator indicative of the figure of merit of the motor operating at the first value of the control variable is compared to a second indicator indicative of the figure of merit of the motor operating at the second value of the control variable. Thereafter, a new value is selected as the first value of the control variable in response to the comparison of the first indicator first to the second indicator.

Abstract: A method of reconnecting a motor to a motor drive comprises controlling a current which flows through the motor using a current regulator. The current regulator produces a voltage command output based on a current command input. A current is commanded at the current command input of the current regulator. Back EMF measurements are acquired at different instants in time by monitoring the voltage command output of the current regulator. Back EMF phase angles are determined for a plurality of the instants in time based on a respective plurality of the back EMF measurements. A frequency of the back EMF is determined based on the back EMF angles determined for the plurality of instants in time. The motor drive is reconnected to the motor based on the frequency of the back EMF.

Abstract: A motor control strategy for use in combination with an electric motor (1) having a number of phase windings (201, 202, 203) is disclosed, the motor (1) being adapted to produce an output torque in response to current in the windings comprising the steps of during normal operation generating a motor torque demand signal indicative of the output torque required from the motor (1), applying a first set of currents to the windings of the motor in response to the motor torque demand signal to produce a first output torque from the motor and during a test operation to enable diagnostics to be performed generating a motor current demand signal indicative of the total current required in the motor windings (201, 202, 203) and adjusting the currents applied to one or more of the windings in response to both the torque demand signal and the motor current demand signal, whereby the adjusted currents produced in the windings are substantially equal to the total current demanded by the motor current demand signal regardl

Abstract: A power electrical system is disclosed for a microturbine power generator. The invention permits the microturbine to be started using an external DC power source. The DC voltage is converted to a variable DC voltage by means of a bi-directional buck-boost circuit, DC bus and a DC-to-AC converter. The DC-to-AC converter produces at its output a fixed voltage pattern whose frequency is gradually increased in concert with the DC voltage, to accelerate the microturbine from standstill to startup speed. Once the microturbine is started, the excitation is discontinued, and the DC bus and DC-to-AC are used to produce output AC power at a voltage level and frequency to match an electrical load.

Abstract: The invention relates to a method for determining the winding temperature (TW) of the stator winding of a three-phase AC motor, in particular a pole-changeable asynchronous motor. For determining the winding temperature (TW) of the stator winding of three-phase AC motors that have an unfavorable ratio of the active power to the dissipation power and react sensitively to temperature changes and changes in a main voltage, and for readily determining the heat dissipation power (PV) from the winding temperature (TW) of the stator winding, it is proposed to determine the reference temperature (TG) and the motor current (IM) simultaneously at consecutive points in time, and to determine the winding temperature (TW) by calculating step-by-step sequentially the change in the winding temperature (TW) at a point in time (tn) and adding this change to the winding temperature (TW) of the immediately preceding point in time (tn−1).

Abstract: A DC motor drive circuit, includes a switching circuit that drives the coils of a small permanent magnetic DC motor. The drive circuit is preferably implemented in an integrated circuit device, such as a silicon CMOS device. Integrated into the same integrated circuit device is a magnetic sensor arranged to detect the position of the permanent magnet as it passes a defined point, or points, in its revolution, and control circuitry to derive the timing waveforms for driving the coils. The integrated power devices for driving the coils are also arranged to limit the rise and fall times of the applied voltages and currents so as to reduce or eliminate the generation of unwanted RFI. Additional circuitry is also integrated into the same integrated circuit device to derive the necessary power to operate the magnetic sensor, the control circuitry and the switching circuitry from the connections between the switching circuitry and the coils so as to remove the need for a separate power supply connection.

Abstract: An AC induction motor is controlled by dynamically matching energy use by the motor to the load on the motor. First and second SCRs are connected in parallel with each other in opposing polarities for each phase of the applied AC voltage. A trigger generator couples trigger control signals to the respective gates of the SCRs responsive to the timing of sensed zero-crossing events of the AC voltage and current in the respective phase applied to the motor winding. The first and second SCRs are alternately triggered into a conductive state during each alternation of the applied AC voltage and are alternately inhibited from the conductive state for an interval in time proportional to a measured difference in time between the AC voltage zero-crossing and the corresponding AC current zero-crossing as determined by comparing the time difference between successive first and second interrupts corresponding to the zero-crossing events with a continuously running time base.