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Ovality Analysis of Large Induction Machine Rotor

In the industry, large asynchronous machines with a squirrel cage rotor are used for the drive of various devices, e.g. pumps, conveyors, presses, etc.

Reliability and trouble-free operation of these machines is an important parameter in the factory and therefore the machine inspection is performed during planned shutdowns. The aim is to predict possible malfunctions and estimate the time period when the machine must be repaired or maintained. One of the most stressed components of the motor is the rotor.

The ovality measurement was done with the horizontal lathe.

In order to display and calculate the ovality map, it is necessary to determine as continuously as possible the coordinates of each point on the rotor surface. Therefore, it was decided to process 22 x 112 = 2464 measurement points on the rotor surface for the map calculation, i.e. each packet along the rotor length (22 in total) and each tooth on the circumference (112 in total)

In this 3D view, the conicity of the rotor is clearly noticeable, with the narrower side being DE (lower) and the looser side NDE (upper).


Particularly, in this planar representation, the release of the packets in the central part of the rotor, where there are no wedges under the slots, is clearly seen.


The RICE (Research and Innovation Center for Electrical Engineering) research team has been dealing with the issue of torque pulsations of motors for more than 25 years and thus contributes to the elimination of problems with drives even in heavy industry. It was specifically a mining machine with a power of 5800 kW. The proposed changes aim to reduce torque pulsations and ensure trouble-free operation of the drive.