Study of Self-starting High-voltage Variable Frequency Electric Drives

The paper compares transient processes of self-starting non-controlled and variable frequency electric drives (VFED) at short-term power supply interruptions. It offers simplified dependencies for calculating duration of transient processes of the individual self-starting asynchronous motor. The study defines reasons for increasing speed recovery time of this assembly. It distinguishes main differences of self-starting the variable frequency and non-controlled electric drives with or without the Flying Start function in the algorithms of the frequency converter. Results of the experimental studies of self-starting high-voltage VFED with the Power Flex 7000 frequency converter are presented. The paper proposes guidelines to provide continuous operation of the essential units at the power supply interruptions. It also emphasizes developments aimed to improve VFED self-starting conditions.