Computer Interfaced Three-Phase Induction Motor Drive

The speed of a three-phase induction motor can be varied within a wide range other than its rated value if its input parameters (frequency, voltages) are varied properly. For industrial, mainly in knitting and some other sophisticated use of three-phase induction motor, precise and accurate control of the speed of the motor is necessary. The present three-phase inverter is so designed that its input parameters can be easily varied through proper software program and computer interfacing hardware. N-channel MOSFET is used as power device but may be replaced with IGBT. A special one way delay circuit is introduced to ensure non short circuit situation. The input frequency to the inverter can be varied by varying the input voltage to the Voltage Controlled Oscillator (VCO). The proper input voltage to the inverter is set by Automatic Voltage Regulator (AVR) instructed by the computer. Though the frequency of the inverter can be varied between a wide range, the inter phase separation remains always 120 deg yielding a true pattern of a three-phase power supply. Introduction of microcomputer and associate of software programs in three-phase induction motor control system is accurate.