METHOD OF DETECTING BROKEN RODS IN SHORT-CIRCUITED WINDING OF ASYNCHRONOUS MOTOR ROTOR Russian patent published in 2019 - IPC G01R31/34 

FIELD: engines and pumps.

SUBSTANCE: invention relates to control of technical state of asynchronous electric motors and can be used for detection of breaks of rods of windings of rotors of asynchronous electric motors. Method includes digital recording of a radial component of induction of an external magnetic field in time using a magnetic field sensor mounted on the motor housing in the zone of the middle of the length of the stator core. Said signal is recorded in start-up mode and divided into intervals. Window Fourier transform is performed at each of said intervals. Duration of intervals is selected considering number of pairs of poles of asynchronous motor, as well as width of main lobe of used window of Fourier transformation. Frequency-time spectrum is obtained. In this spectrum determining presence of harmonic components of fictitious winding of rotor at lower lateral frequencies, defined by expression:

where is the lower side frequency of the fictitious winding of the rotor νth order Hz, t – current time at start-up, 0≤t≤T, c, T is duration of induction motor start, s; ƒ_n – network frequency, Hz, s(t) is the rotor slip; p is the motor poles pairs number; ν is harmonic order. In the presence of said harmonic components, a signal is generated on the presence of the breakage of the rotor winding core.

EFFECT: high reliability of monitoring results while broadening functional capabilities.

1 cl, 6 dwg, 1 tbl