Abstract: An electric motor driving system has a permanent magnet type synchronous motor, an inverter for driving the motor, a generator for issuing a rotational frequency command to the motor and a controller including a conversion gain for generating a control signal to the inverter on the basis of the rotational frequency command, an integrator, a zero generator, a qc-axis voltage command arithmetic unit, a dq inverter, a dq coordinate converter, a high-pass filter, and an adder, wherein the system includes the high-pass filter for correcting the rotational frequency command to the motor on the basis of current detection values flowing through the motor, and a step-out detector for comparing the correction amount with a threshold value previously set for the coordinate amount to judge when the correction amount exceeds the threshold value at least one or more times that the motor is in the step-out state.

Abstract: An electric motor driving system has a permanent magnet type synchronous motor, an inverter for driving the motor, a generator for issuing a rotational frequency command to the motor and a controller including a conversion gain for generating a control signal to the inverter on the basis of the rotational frequency command, an integrator, a zero generator, a qc-axis voltage command arithmetic unit, a dq inverter, a dq coordinate converter, a high-pass filter, and an adder, wherein the system includes the high-pass filter for correcting the rotational frequency command to the motor on the basis of current detection values flowing through the motor, and a step-out detector for comparing the correction amount with a threshold value previously set for the coordinate amount to judge when the correction amount exceeds the threshold value at least one or more times that the motor is in the step-out state.

Abstract: An inverter apparatus operatable over an extended output frequency range having an increased upper limit with error contained in the output voltage being suppressed by eliminating dispersions of PWM pulse signals. A PWM command pulse signal and an output voltage detection signal derived from the output of the inverter are compared straightforwardly with each other for determining difference therebetween on the basis of which error contained in the inverter output voltage is canceled. An isolation device for isolating electrically a low-voltage-rated control circuitry and a high-voltage-rated main circuitry from each other is inserted between a PWM command pulse signal generating circuit and a pulse width correcting circuit.