Comparison of Test Methods for Characterization of Doubly Fed Induction Machines

The doubly fed induction machine (DFIM) is widely used in variable-speed ac drives. Accurate characterization of the machine is important to optimize its efficiency and operation. A novel characterization method using series-coupling tests has produced favorable results in characterizing this type of machine. This paper reviews the series-coupling tests and compares their results with IEEE Standard 112. The conventional IEEE Standard 112, series-coupling, and extended-short-circuit testing procedures are used to characterize a 1.1- and a 30-kW DFIMs. The various models obtained from these methods are validated by comparing the model predictions with the experimental torque-speed curve for each of the machines. The series-coupling test approach offers a more direct method of obtaining the various resistive and inductive elements than the other testing procedures, and this is reflected in the performance of the series-coupling test models in predicting the torque-speed curves of the two machines. The series-coupling test was found to predict the torque profile of the 1.1-kW machine with a higher degree of accuracy than the other test models while having similar accuracy to the IEEE tests in the case of the 30-kW machine. A sensitivity analysis of the test procedures is carried out to determine the influence the errors in experimental measurements have on the respective models and to subsequently determine the suitability of each test procedure for characterizing each of the machines. Finally, the variation of the parameters with applied test conditions in the series-coupling procedure is investigated.