Intelligent PWM inverter for induction motor control

Transvector control is an established technique enabling induction motors to operate in a wide speed range. The disadvantages of this method are connected with the evaluation or the direct measurement of the motor flux and with the sophistication of the required control technique. Starting from the `field acceleration method´ (FAM) suggested by S. Yamamura (1986), the authors have developed a new technique which employs rotor current feedback (FAMRCF) which simplifies the control system and leads to superior performance as compared to that obtained with other solutions. A new squirrel cage rotor current transducer was developed and the rotor flux was measured indirectly. Through stator current control the rotor flux magnitude is maintained constant and by accelerating or decelerating the rotor flux vector, the electromagnetic torque and consequently, the motor speed are easily controlled