An introduction to electric machine modeling by systems of noninteger order. Application to double-cage induction machine

The flowing of induced currents in electric machines, especially in the deep-bars of induction machine cages and the dampers of synchronous machines, implies an increase in the order of the equivalent circuits used to model their frequency response. But, physical meanings of the circuit parameters are often lost. Thus, the authors propose to go back over the modeling of skin effect in order to define noninteger order equivalent circuits which would be linked with the consequences of induced currents on the frequency response. In this paper, the proposed equivalent circuit is based on half-order systems. It is used to represent the frequency response of a 30 kW 4 pole double-cage induction machine and its results are compared with measurements.