Variable frequency drive and rotation speed searching apparatus for an induction motor

摘要

Provided is a variable frequency drive and a rotation speed searching apparatus for an induction motor incorporated therein. The rotation speed searching apparatus is featured by scanning the rotor frequency of the induction motor and determining either the error between a detected DC-bus voltage and a set DC-bus voltage or the error between a detected output current and a set output current, so that the rotation speed of the induction motor can be searched out.