ABSTRACT
Induction machines (IMs) contain magnetic circuits travelled by A.C. and travelling magnetic fields and electric circuits flowed by alternative currents. The electric circuits are insulated from the magnetic circuits (cores). The insulation system comprises the conductor insulation, slot, and interphase insulation. At frequencies encountered in IMs (up to tens of kHz, when pulse width modulation inverter fed), the insulation losses are neglected. Soft magnetic materials are used in IM as the magnetic field is currently produced. Energy loss in the magnetic material itself is a very significant characteristic in the energy efficiency of IMs. Traditionally, core loss has been divided into two components: hysteresis loss and eddy current loss. Though the rotor cage bars are in general uninsulated from the magnetic core, most of the current flow through the cage bars as their resistivity is more than 20–30 times smaller than that of the laminated core.
