METHOD FOR DETECTION OF BROKEN RODS IN SHORT-CIRCUITED ROTOR WINDING OF ASYNCHRONOUS ELECTRIC MOTOR Russian patent published in 2022 - IPC G01R31/34 

FIELD: technical condition monitoring.

SUBSTANCE: invention relates to the field of monitoring the technical condition of asynchronous electric motors and can be used to detect breaks in the rods of the rotor windings of high-voltage asynchronous electric motors. A method for detecting broken rods in a short-circuited rotor winding of an asynchronous electric motor includes digital registration of the radial component of the induction of an external magnetic field in time using a magnetic field sensor installed on the motor housing in the area of the middle length of the stator core, dividing the received signal into intervals, conducting at each of these intervals of the windowed Fourier transform and obtaining the time-frequency spectrum. In this case, the signal is recorded in the run-out mode, the duration of the intervals ΔT, into which the recorded signal is divided, is determined from the condition

where X_RW is the inductive resistance of the rotor winding, Ohm; R_RW - active resistance of the rotor winding, Ohm; _Snom - nominal rotor slip, r.u., ƒ_m - mains frequency, Hz; ΔF is the relative width of the main lobe of the window used compared to the width of the main lobe of the rectangular window; p is the number of motor pole pairs. The presence of harmonic components from the fictitious winding of the rotor is determined in the frequency-time spectrum, excluding harmonics of the order coinciding with the number of pairs of poles, the frequencies of which in the run-down mode are determined by the expression

where ν=1, 2, 3, 4, 5… - harmonic order; n(t) - speed of rotation of the asynchronous electric motor at time t, rpm. In the presence of these harmonic components, a signal is generated about the presence of a break in the rotor winding rod.

EFFECT: creation of a reliable and safe method for detecting broken rods in a short-circuited rotor winding of a high-voltage asynchronous electric motor with a quick start, lasting less than 3 seconds.

1 cl, 2 ex