A Stator Current Locus Approach to Induction Machine Parameter Estimation

Induction machines are an attractive alternative to permanent magnet machines in transportation applications due to their ruggedness and lower cost of construction. However, high-performance control of induction machines requires accurate knowledge of the machine parameters. While parameters have traditionally been identified using the standard "no-load" and "locked-rotor" tests, these tests are not representative of normal operating conditions, and are not well suited to the commissioning of variable speed drives. This paper presents a new method for induction machine parameter identification using steady-state measurements, which is based on fitting data to the stator current locus for various slip frequencies. Numerical results confirm the method's high accuracy, while experimental results demonstrate its ability to characterize an induction machine over a range of flux levels which include magnetic saturation.