| Abstract |
Variable speed drives (VSDs) offer reduced power consumption for applications which allowoperation at reduced motor speed. However, when continuous operation at the grid frequencyis required, the VSD may become redundant, as it introduces conversion losses and electromagneticinterference (EMI), in contrast to grid-connected operation. It is hereby proposed to bypass theVSD for continuous operation at the grid frequency. This paper introduces a VSD, based ona two-level voltage source inverter (VSI), capable of transferring a motor load between grid- andinverter-connected operations, depending on the required motor speed. This paper presents athorough analysis of the conditions under which the motor load may be transitioned from eitheroperating mode. Thyristors are used as bypass devices. Simulation results for open and semi-closed transitions are presented, examining their impacts on the motor torque and stator currents. |
