METHOD OF DETECTING INCREASED ECCENTRICITY OF ASYNCHRONOUS ELECTRIC MOTOR Russian patent published in 2024 - IPC G01R31/34 

FIELD: measurement.

SUBSTANCE: invention relates to monitoring of technical condition of asynchronous electric motors and can be used for detection of increased eccentricity of asynchronous electric motors with runout duration of not less than 10 s. Parameters of the external magnetic field of the machine are measured in the runout mode. Harmonic components are separated. Recorded signal is divided into intervals ΔT, the duration of which must be in the range, which is determined by the expression: where t₁ is the moment of time at which the rotation speed is halved, s; n_c is synchronous speed of rotation of asynchronous motor, rpm; ΔF is the relative width of the main lobe of the used window compared to the width of the main lobe of the rectangular window; p is the number of pole pairs of the asynchronous motor, and the frequency-time spectrum of the recorded signal is generated using a windowed Fourier transform. Determining the time moment at which currents in the rotor winding are damped, according to the expression: where X_RW is inductive resistance of rotor winding, Ohm; R_RW is active resistance of rotor winding, Ohm; s_nom is the rotor nominal slip, p.u., ƒ_c is network frequency, Hz. Determining in the spectrum of the amplitude of the harmonic components of the dynamic eccentricity, starting from the time T_damp from the beginning of the runout, the frequencies of which in the runout mode are determined by the expression: where ƒ_fund(ƒ) is the value of the signal fundamental harmonic frequency at the moment of time t, rpm; v is order of dynamic eccentricity harmonic; is the value of the upper and lower lateral frequencies of the harmonic of the dynamic eccentricity of the v-th order at the moment of time t, Hz. A computer model of the investigated engine is created in the presence of a dynamic eccentricity making 10% of the air gap value. Threshold values of amplitudes of dynamic eccentricity harmonics are determined on a computer model. If the amplitude of at least one of the harmonic of threshold values is exceeded, a conclusion is made on the presence of increased eccentricity of the asynchronous motor.

EFFECT: improving reliability of determination of eccentricity of asynchronous electric motor.

1 cl, 4 dwg, 2 tbl