Performance of a single-phase to three-phase cycloconvertor drive

Abstract

The paper presents the performance of a three-phase induction motor driven by a new cycloconvertor consisting of six naturally commutated triacs and digital control circuits, which can generate a symmetrical variable voltage variable frequency (VVVF) three-phase supply from a single-phase mains. This inexpensive topology is particularly suitable for low power domestic and similar drives requiring full torque and/or regenerative operation over the full speed range. Using a double integral control technique, a single-phase to three-phase modulation strategy is proposed so the phase flux linkages follow sinusoidal references. The output frequency of this cycloconvertor can be up to half of the input frequency, giving a maximum synchronous speed of 1500 rev/min for a two-pole motor. The three phase currents are symmetrical, and the motor speed ripple is low. Despite a reduced efficiency and power factor, the torque-speed curve of the motor with the cycloconvertor supply is very close to that with a sinusoidal supply. Software was written in C for both simulation and control. The experimental results agree with the simulation.