Starting torque of variable frequency electric drive

The thesis deals with analyzing modes of the induction motor breakaway in the system “frequency changer - induction motor”. The authors establish that the stator winding heating occurs slower when forming the cyclic starting moment compared to the heating in the prolonged operating mode of the induction motor with the stalled rotor that allows doing multiple breakaway attempts with increasing the starting moment due to the short-terms excess of the starting moment value. The conducted experiments of the induction motor capabilities powered with frequency changer determine that there is such correlation between frequency and supply voltage when receiving values of the starting moment with the specified overload coefficient that the stator current has a minimal value.