In the paper the case of the squirrel cage failure in high voltage induction motor is described. This motor is operating in the drive characterised by long starting time and by very high and frequent overloads. The analysis of drive operation and reasons of failure curried out. The changes in rotor construction has been proposed to increase the motor service life.
The damages of the induction motor rotor's squirrel-cage winding in most cases accumulate gradually, so it is possible to detect them early and protect the user effectively from the damages' consequences. When the induction motor with an asymmetrical rotor is operating with the constant power output, various negative effects can occur, the most serious of which are the decrease in the efficiency and the increase of the motor's temperature. The issue of the steady state occurring in such cases has been discussed in numerous articles, but the majority of them confine themselves to the simulations based on the mathematical model. One of the main objectives of this paper is to investigate experimentally the operating of the motor with a damaged squirrel-cage winding in the transient states. In this article the results of the laboratory tests of the transient states (start-up, reversion) of the cage motor's model are presented. The special construction of the physical model allows for intentional liquidation of the galvanic connection between the bar and the end ring. During the start-up and reversion the torque of the motor, the current of the stator and the motor speed have been measured. The results of the tests carried out on the model of the rotor with various degrees of damages to the squirrel-cage winding are presented. Moreover, the case in which the located together bars are broken is compared with the situation in which the number of the broken bars is equal, but the damage has the property of being symmetrical, and also when it is random. Finally, the conclusions presenting the possible means of diagnosing such damages are drawn.
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