Including frequency dependent iron losses in analytical models of induction machines

摘要

The objectives of the project are two-fold. First, appropriate models and tests should be developed to calculate core losses analytically and understand their dependency on frequency. Second, algorithms must be developed to solve the standard machine and core loss parameters.To reach these objectives, small-signal models for the standard machine parameters will be utilised. Small-signal models including core loss parameters will be developed and verified. Core losses will be determined for a 37kW machine from Finite Element Analysis (FEA) at various voltage and frequency points. The results will be used to determine core loss parameters via the steady-state and developed small-signal models. Finally, a DC step voltage test will be utilised, along with an induction machine model at standstill, to determine machine parameters.Three algorithms to determine the machine parameters, based on impulse voltage tests, are presented and compared. The first uses core loss resistance models with a fixed Steinmetz coefficient in small-signal and steady-state models of the induction machine. The second uses core loss resistance models with a variable Steinmetz coefficient. The third algorithm uses the same models used in the second algorithm; however, results of the step voltage tests are used to improve the speed of the algorithm. Furthermore, this algorithm allows all machine parameters to be determined independently. Specifically, the relationship between the stator and rotor leakage inductance need not be known.The challenges faced in determining the aforementioned parameters will also be outlined. Ideas and algorithms to tackle these challenges will be presented. The use of the DC step voltage test to improve the parameter estimation process will be explained. A complete algorithm, using differential evolution and two forms of fixed-point iteration for determining the core loss parameters, will be outlined.