Monitoring the condition of the short-circuited rotor winding rods of an asynchronous electric motor

The breakage of the short-circuited rotor winding rods of an asynchronous electric motor is currently the most common type of rotor damage, which requires early diagnostics to prevent its complete failure. Existing methods to monitor the actual state of the short-circuited rotor winding of an asynchronous motor are usually based on the use of spectral analysis which has a number of disadvantages, or on the use of expensive special sensors, the installation of which is not always possible under the operating conditions of the electric motor. Thus, it is important to identify a diagnostic sign of a breakage of the rotor rods based on the measured currents and voltages without using additional special sensors and analyzing the obtained spectral characteristics. To achieve the set task, a computer modeling method has been applied using a multi-loop mathematical model of an asynchronous electric motor, recorded using a system of differential equations. The author has proposed a criterion to monitor the condition of the rods of the short-circuited winding of the rotor of an asynchronous electric motor without decommissioning. It is based on identifying characteristic fluctuations of the angle between the generalized vector of the stator current and the generalized vector of the supply voltage, obtained on the basis of instantaneous measured values of currents and voltages. The results obtained using computer modeling have shown that the proposed criterion to detect a breakage in the short-circuited rotor winding rods of an asynchronous electric motor is sensitive enough to detect a breakage in both one rod and several rods. Using the proposed criterion to monitor the actual state of the short-circuited rotor winding rods of an asynchronous electric motor allows us to avoid the installation of expensive sensors on the motor housing and refuse to carry out complex spectral analysis.