A method to estimate parameters of five-phase induction machines including the third-harmonic airgap field

Abstract

We propose a method to estimate all electrical parameters of five-phase induction motors based on a new concept of instantaneous impedance. Only stator voltages and currents acquired during no-load startup tests are required to determine the parameters of the fundamental and third-harmonic equivalent circuits. Additional quantities, such as rotor speed and electromagnetic torque, are also estimated from measurements. Unlike similar procedures, the parameters of the third-harmonic circuit are estimated separately from the parameters of the fundamental circuit, thus making the estimation more accurate. To experimentally validate the method, we tested a 4.5-kW and a 5.5-kW prototype using sinusoidal as well as trapezoidal voltages generated by a static converter. One of the main advantages of the proposed procedure is the possibility of using data acquired also with a static converter. Besides, to validate the method as well as to assess the accuracy of the estimated parameters, we first simulated the machine behavior using the estimated parameters and the measured stator voltages as input and subsequently compared the simulated currents with those acquired during no-load startup and load tests. Furthermore, we implemented a closed-loop Rotor Field Oriented Control (RFOC) scheme using both calculated and estimated parameters and then compared the controller performance with both sets of parameters. The practical results demonstrate not only that the method provides accurate estimates for all parameters but also that the use of the estimated parameters can improve the performance of the controller.