A low cost method for generating constant volts per frequency control signals

摘要

This paper proposes a Volts/Hz control scheme applicable in speed control of inverter-fed induction motor. The method effects simultaneous control changes in the frequency and voltage of a 3-phase inverter at a constant ratio. The system is composed of 3 sections namely: the boost converter, the three-phase inverter and the control circuit. A dc voltage level, changes the duty cycle, thus the voltage of the boost converter which is fed to an inverter, and simultaneously changes the fundamental frequency output of the inverter at a constant rate. Thus a constant voltage per frequency control is achieved to obtain maximum torque at zero speeds in induction motors. The system was designed and tested in laboratory conditions with satisfactory results.