METHOD FOR DETERMINING ROTOR SPEED OF ASYNCHRONOUS MOTORS Russian patent published in 2020 - IPC G01P3/48 

FIELD: electrical engineering.

SUBSTANCE: invention relates to the field of electrical engineering, in particular to measurement of parameters of asynchronous motors. A method for determining rotor speed of induction motors supplied by frequency converters when tested by mutual load task includes the number of rotor grooves Z₂ and p of pole pairs of the asynchronous motor, after that instant voltage and current values of one phase of asynchronous motor stator are measured, and voltage and current spectra are calculated. Further, the current spectrum amplitudes are divided into corresponding amplitudes of the voltage spectrum, after which four ranges of search for rotor tooth harmonics with numbers n=1, 2, 3, 4 are calculated, each of which has an upper frequency limit f_lim1n and a lower frequency limit f_lim2n, then frequencies f_Zn of tooth harmonics of the rotor are determined, and according to the found frequencies there calculated is slippage s and rotation frequency of the asynchronous motor rotor. At that, for calculation of search ranges of tooth harmonics of rotor there used are values of frequencies (ƒ₁ and ƒ₂) voltages supplying asynchronous motors, obtained from frequency feed frequency detectors built into frequency converters; wherein upper limit of n-th search range is determined by expression ƒ_lim1n=ƒ₁Z₂/p+ƒ₁k, and lower limit of n-th search range is equal to ƒ_lim2n=K_Δ(ƒ₁+ƒ₂)Z₂/2p+ƒ₁k, where K_Δ<1 is a coefficient which takes into account the slip determination error, based on the arithmetic mean value of frequencies ƒ₁ and ƒ₂.

EFFECT: use of the proposed device will make it possible to reduce costs of computational resources while providing a high level of automation in the process of determining the rotor speed of asynchronous machines when tested by mutual load with power from frequency converters.

1 cl, 1 dwg