Imbalance Characteristics of Full and Part Winding Excited Double Sided Linear Induction Machine

In the analysis of double sided linear induction motor (DLIM) for use in high speed ground transportation schemes, it is known that unbalanced currents flow in the various phases of DLIM even when balanced voltages are applied at the motor terminals, static and dynamic end effects being the cause. However, the final electrical equivalent circuit representation reported has invariably been a per phase circuit analogous to the equivalent circuit of the rotary machine counterpart where this phenomena is absent. The paper presents a valid harmonic equivalent circuit representation through critical study of Mosebach´s methodology which is based on the Fourier harmonic technique and superposition of the forward and backward travelling waves set up by the stator current sheets. Certain interesting properties of such an equivalent circuit are first discussed and then, for the 2500 HP DLIM, comparision between predicted and experimental imbalance characteristics are presented for full 10 pole as well as diverse part winding excitations.