Implementation of a novel fuzzy rule-based protection for an inverter fed induction motor

A novel fuzzy rule based smart protection for an inverter fed induction motor drive is proposed. Two protection schemes are proposed, implemented and tested. The first scheme uses the inverter input current I/sub dc/ and its rate of change /spl Delta/I/sub dc/ to evaluate the drive condition according to a fuzzy rule base. In the second scheme, the rate of change of the motor speed is used instead of /spl Delta/I/sub dc/. The fuzzy output, which is a time delay, is defuzzified, then used to control the time intervals at which the protection circuit is required to watch the drive. These intervals become shorter if the drive condition is estimated to aggravate. If they drop below a certain limit, the drive gating signals are momentarily blocked.