Saturation effects in three-phase induction motors
Akbaba M., Fakhro S.Q.
SourcetitleElectric Machines and Power Systems
An analytical method for the calculation of the effect of magnetic saturation on the leakage reactance of three-phase induction motors is developed and confirmed by experiment. The method is based on assuming an equivalent magnetic circuit and representing the true magnetising characteristic of the iron forming the magnetic circuit, by an analytical function. Since the saturation of the leakage flux paths is related to the geometry of the tooth-tips and to the form of the slot openings, all three types of slot openings, i.e. open, semi-closed and closed, are considered in detail. Using the assumed equivalent magnetic circuit and the true magnetising characteristic together with the design details, the total leakage flux passing through the selected saturable areas is calculated and resolved into its various components. i.e. zig-zag, skew, slot leakage fluxes. From these the associated leakage reactance components are evaluated and the total leakage reactance is formed. The method has been applied to a 3-phase, 5.5 KVA, 440 V, 4 pole cage induction motor having 36 semi-closed slots on stator and 24 closed slots on the rotor. The variation of the total leakage reactance with winding current as well as transient torque are calculated and compared with experimental results. � Taylor & Francis Group, LLC.