Numerical and experimental investigation of bridge currents of an induction machine equipped with bridge configured winding

Authors:
Sivaramakrishnan Natesan, Karuna Kalita, Venkatesu Samala
Department of Mechanical Engineering, Indian Institute of Technology Guwahati, and ICON Design and Automation, Bangalore, India

Abstract:
An eccentric rotor motion imbalances the magnetic field distribution in the air-gap region. Due to this uneven flux density distribution, a net radial force called Unbalanced Magnetic Pull (UMP) is in action towards the shortest air-gap. This UMP can degrade the machine’s performance. UMP can be controlled by a special kind of winding called Bridge Configured Winding (BCW). The BCW winding is a single set of winding which is used to produce the torque as well as the controllable force. The main contribution of this paper is to inspect the flow of bridge currents in the bridges when the machine is having rotor eccentricity or unbalance. The bridge currents in the presence of rotor eccentricity with the stator of an In­duction machine model has been analyzed by using an Electromagnetic Finite Element (FE) solver called Opera 2D/RM solver (Rotation Motion Analysis). The bridge currents have been measured for two different cases., (i) Induction machine model with zero eccentricity, (ii) Induction machine model with 10% static eccentricity of the air gap. Experimental re­sults are presented for the validation of Opera 2D/RM results. A modified 37kW Induction machine has been used for this study. A known mass unbalance is introduced in the perfo­rated disc in order to create the unbalance in the system purposefully. The bridge currents have been measured and compared with and without unbalance present in the system. The comparison of measured bridge currents for all the cases are given in the frequency domain.

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