Dynamic Behavior of Series-Connected Wound- Rotor Induction Motors in Super Synchronous Mode Considering Magnetic Saturation

Abstract

Series-connected wound-rotor induction motor (SCWRIM) delivers a unidirectional electro-magnetic torque under two distinct operational modes. The first mode is known as super synchronous speed since the rotor speed there is precisely twice the synchronous speed. In this mode, the rotor speed relies solely on the frequency and number of poles to maintain stable operation with absence of starting torque. Consequently, in order to achieve the double synchronous speed, additional arrangements need to be implemented. In the second mode of operation, SCWRIM rotates at an extent slower than the synchronous speed depending on the employed load. This process is hence referred to as sub-synchronous mode. The motor behaves similarly to a traditional wound rotor induction motor when operating in this mode. The aim of this paper is to present a dynamic analysis of a three-phase SCWRIM taking into account the nonlinearity effect due to saturation phenomena. This model could be suitable for steady-state, dynamic response balanced and unbalanced conditions. For more realistic representation, the influence of magnetic saturation is considered in both direct and quadrature axes in this proposed model. Eventually, the validity and efficiency of the suggested method of incorporating the magnetic saturation effect are shown by contrasting the simulation results with experimentally obtained values.