Fuji Electric Co., Ltd.

Fuji Electric Systems Co. Ltd.

Hidetoshi Umida

Hirokazu Tajima

Hiroshi Tetsutani

Shinichi Ishii

Junichi Itoh

Junichi Ito

Akio Toba

Takashi Aihara

Akihiro Odaka

Yasushi Matsumoto

Sho Takano

Hiroyuki Yonezawa

A gate drive circuit includes a signal generation unit configured to generate a first gate drive signal, a signal isolation unit configured to produce, at an output side thereof in response to the first gate drive signal, a second gate drive signal electrically isolated from the signal generation unit, an output stage device configured to receive the second gate drive signal at an input side thereof and to produce a third gate drive signal at an output side thereof in response to the second gate drive signal, a first path connecting the output side of the signal isolation unit and the input side of the output stage device; and a second path connecting the output side of the signal isolation unit and the output side of the output stage device.

Gate drive circuit

A control method of an inverter for outputting polyphase alternate-current electrical power is provided. In the control method, modified PWM pulses of respective phases for controlling semiconductor switching elements of the inverter are generated, based on an output of a counter common to the respective phases. Each of the modified PWM pulses is configured such that a total pulse width, in a period corresponding to one or more cycles of a carrier, is substantially equal to a total pulse width of an assumed PWM pulse which is obtained by comparing, with the carrier, a time average value of an output voltage of the corresponding phase in the period. Further, at least one of a generation timing and a generation frequency of at least one of the modified PWM pulses is changed from the assumed PWM pulse.

Inverter that adjusts voltage command values and control method of inverter

The driving apparatus according to the invention includes an inverter that drives multiple induction motors connected in parallel, and a secondary current calculating circuit that calculates the components iand iof a total secondary current value, which is the sum of the secondary currents of all the motors. The apparatus further includes a current deviation quantity calculating circuit that calculates a deviation quantity, for which the total secondary current value deviates from a reference trace. A torque regulating circuit regulates the motor torque based on the calculated deviation quantity. The driving apparatus for driving multiple induction motors according to the invention facilitates quickly detecting the widening caused in the rotating speed differences and preventing the rotating speed differences from widening.

Driving apparatus for driving multiple induction motors

The present invention provides a variable-speed controlling device for use with an induction motor, which includes a means for compensating for the discrepancy between a secondary magnetic flux instruction value and a secondary magnetic flux actually occurring in an induction motor, realizes a satisfactory control by generating the secondary magnetic flux according to the instruction value, and can generate desired torque and improve a motor efficiency. The variable-speed controlling device according to the present invention, for use with an induction motor, includes a voltage instruction value calculating unit, an integrating unit, a power converting circuit, a current detecting unit, an induced voltage calculating unit, a position discrepancy amount calculating unit, and a compensating unit.

Variable-speed controlling device for use with an induction motor

A control apparatus for estimating the flux, the current, and the speed of an AC motor using the current and the voltage, and controlling the vector of an AC motor using the estimated speed, a flux command, and a torque current command. The speed is estimated by adding a product of the deviation between the actual value and the estimated value of a magnetization current, the level of a torque current correspondence value, the sign correspondence value of a primary frequency command value, and a gain to an outer product of an estimated current deviation and an estimated flux. Thus, a stable speed estimating operation can be performed to successfully operate the motor in a low speed area in which a voltage frequency applied to the motor is extremely low.

Speed sensorless vector control apparatus

A PWM power converter is provided which includes an adder that adds a high-frequency signal from a high-frequency generator to a voltage command signal, and a PWM generator of carrier comparison type or space vector type that generates a PWM signal based on the output of the adder, which PWM signal is used for driving switching devices to provide a desired output voltage.

PWM power converter

A control apparatus for variably controlling a speed of an induction motor includes a voltage generator, adders, a rotating speed calculating device, a rotating direction detecting device, and a multiplier. The voltage generator is operated for a predetermined period of time at the start or restart of the induction motor to cause self-excited oscillation in a control system including the voltage generator, the induction motor and the PWM inverter. The rotating speed calculating device obtains the rotating speed data, and the rotating direction detecting device detects the rotating direction of the induction motor based on the .alpha.- and .beta.-axis components, on the stationary coordinate, of the primary current of the induction motor. And, the PWM inverter is started based on the obtained rotating speed data and rotating direction. The control apparatus facilitates starting the PWM inverter that supplies electric power to the induction motor or restarting the PWM inverter after the AC electric power supply to the PWM inverter has recovered from a momentary service interruption.

Control apparatus for variably controlling speed induction motor

When an induction motor is variable-speed-controlled via an electric power converting circuit, the magnetic flux of the induction motor is modulated by adding an alternating current signal to, for example, a magnetizing current command. For example, the component depending on the slip frequency of the induction motor is extracted by an extracting means from at least one of the amounts of changes of the voltage, the electric current, and the magnetic flux, which are caused by the modulation of the magnetic flux. The amount of the voltage or the electric current supplied to the motor, etc. is controlled based on the extracted component via an adjusting unit and a control means, thereby implementing superior control of the induction motor.

Variable speed controlling device for induction motor

A variable-speed control apparatus computes the leakage inductance of an AC motor, correctly compensates the leakage inductance, and controls the variable speed of the AC motor. The variable-speed control apparatus has an AC signal generation circuit for generating an AC signal, and obtains a leakage inductance calculation value of the AC motor based on the AC signal and the measured actual current value. The differential value of the summation of a current command value and the AC signal is multiplied by the leakage inductance calculation value to generate a signal for use in compensating the voltage drop caused by the leakage inductance, and added to a voltage command value to cancel the deviation between the actual current value and the M-axis current command value and to obtain the second voltage command value. The second voltage command value is converted into a 3-phase voltage command value and used in controlling the AC motor, and the voltage drop caused by the leakage inductance can be compensated.

Variable-speed control method and apparatus for AC motor

To provide a trans-vector controller for an alternating current ('AC') motor that facilitates operating the secondary resistance of the AC motor without experimentally rotating the AC motor. In a preferred embodiment, the variable speed control circuit, including a secondary resistance value generating device, changes the direct current ('DC') exciting current and operates the secondary resistance of an induction motor by superimposing an AC signal with small amplitude outputted from a AC signal generator onto a reference current value immediately before the start of the induction motor in the state of DC excitation.

Variable speed controller for an AC motor

A variable speed controller for an induction motor that estimates the primary angular frequency and the speed without causing any error in the drive region where the induced voltage is low. The primary angular frequency and speed estimating device includes: a changeover signal generator that generates a changeover signal indicative of a first mode of operation when the induced voltage is greater than the changeover threshold, and a second mode of operation when the induced voltage is less than the changeover threshold; a differentiator, filter, etc., for estimating the load torque; a sample holder that holds the estimated load torque in the second mode of operation; an adder that generates the acceleration and deceleration torque; an integrator that integrates the acceleration and deceleration torque with the mechanical time constant of the induction motor to obtain the second generated speed; an adder that generates a second primary angular frequency; and an output device that in the first mode of operation outputs the first generated primary angular frequency as the reference primary angular frequency and the first generated speed as the estimated speed, and in the second mode of operation outputs the second generated primary angular frequency as the reference primary angular frequency and the second generated speed as the estimated speed.

Variable speed controller for an induction motor

A control apparatus for conducting a variable speed control of an AC motor by controlling an M-axis component and a T-axis component of a current flowing through the AC motor. The control apparatus comprises: M-axis current regulator for executing proportional plus integral computation on a difference between an actual value of the M-axis component and an M-axis current reference value to obtain an M-axis proportional value and an M-axis integration value, and for determining an M-axis voltage reference value by adding the M-axis proportional value to the M-axis integration value; T-axis current regulator for executing proportional plus integral computation on a difference between an actual value of the T-axis component and a T-axis current reference value to obtain a T-axis proportional value and a T-axis integration value, and for determining a T-axis voltage reference value by adding the T-axis proportional value to the T-axis integration value; and a renewal coefficient computing device for computing a vector sum of the M-axis voltage reference value and the T-axis voltage reference value, and determining a renewal coefficient for renewing the M-axis integration value and the T-axis integration value based on the relation between the vector sum and a predetermined output voltage limit value.

Control apparatus for AC motor

Disclosed are methods and apparatus for quickly measuring a primary resistance value of an AC motor without using high precision detectors and detecting malfunctions such as breaking of wire in the AC motor or in a power converting mechanism, open phase, and three-phase unbalance. A voltage drop attributable to the primary resistance of the AC motor can be estimated by using an estimated resistance value R.sub.1.sup.#, which is estimated in turn by an integral or proportional-plus-integral operation on the deviation between a detected magnetizing current value I.sub.M and a reference magnetizing current value I.sub.M *, in place of an actual primary resistance value R.sub.1. The time for the estimated resistance value R.sub.1.sup.# to reach the true primary resistance value is reduced with a varying reference magnetizing current value I.sub.M **. Variations of the estimated primary resistance values R.sub.1.sup.# s between the phases are corrected with a mean estimated primary resistance value R.sub.1M.sup.# according to a reference phase value .phi.*. Malfunctions such as open phase and breaking of wire are detected by comparing estimated primary resistance values obtained according to the reference phase value .phi.*.

Method and apparatus for controlling an AC motor and detecting

An apparatus for driving an AC motor at variable speeds facilitates arbitrary setting or adjustment of equivalent primary resistance of an AC motor. In one embodiment of the present invention, a reference AC voltage generator outputs reference AC voltage values for each phase of the AC motor, and signals derived from the reference voltage values are in turn used by a power converter to supply the AC motor with variable voltage and frequency. In this embodiment, two or more phase currents are fed back to, and subtracted from, the reference voltage values via a regulator. In another embodiment, an angular-frequency/biaxial-reference-voltage value generator generates a reference primary angular frequency value and biaxial reference voltage values of the AC motor in a rotating orthogonal coordinate system. In this embodiment, two or more of the AC motor's phase currents are fed back to, and subtracted from, the biaxial reference voltage values via a vector transformer and a regulator. The present invention not only avoids power loss associated with using resistors, but it also obviates manual, apparatus-by-apparatus adjustment of reference AC voltage values used to drive a given AC motor.

Apparatus for driving an AC motor at variable speeds

A variable speed control for induction motors with a primary angular frequency operating circuit has a multiplier that multiplies the output of a first regulator by a variable responsive to magnetic flux intensity. This first regulator holds the M axis induced voltage at zero. The primary angular frequency operating circuit corrects the primary angular frequency command value based on the output of the multiplier. An adder adds the output of a second regulator circuit and the output of the primary angular frequency operating circuit. The second regulator regulates (by proportional or proportional-integral control) the deviation between the command value of the torque current, or the torque and an actual value, to zero. In another embodiment, the magnetic flux operating circuit calculates a first value and a second value. The first value is obtained by adding a result of multiplication of a reference frequency value by a magnetic flux command value and an absolute value of an induced voltage or a T axis induced voltage. The second value is the sum of the reference frequency value and an absolute value of the primary angular frequency command value. The magnetic flux operating circuit divides the first value by the second and obtains a calculated magnetic flux value by passing the result of the division through a low pass filter. The calculated magnetic flux value serves as an equivalent of the magnetic flux, which is a necessary input of the primary angular frequency operating circuit and the magnetic flux regulator.

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Tokyo, Japan

Hidetoshi Umida