Analysis of induction machines under rotor end-ring faults

Based on the multi-loop theory, this paper analyzes the current change in each inner part of rotor windings under rotor broken end-ring fault of cage induction machine and summarizes change rule. At first, this paper establishes the fundamental machine winding equation for fault analysis and gives the analysis method of rotor broken end-ring fault; then the paper analyzes respectively the change rule of machine inner current under one broken end-ring fault, two broken end-rings fault on the same side of rotor, two broken end-rings fault on the different sides of rotor and under the concurrent fault of broken bar and broken end-ring. The paper points out the severe unsymmetry of the end-ring current on the side of broken end- ring after end-ring breaks and gives current change rule definitely; since the rotor bar current is smaller than it in normal condition, the output power of machine will decrease, and the increases of individual bar current can cause machine torque to fluctuate and to move unsteadily. In addition, this paper gives the value of fault character current component in stator winding after broken end-ring fault.