METHOD FOR DETERMINING INDUCTION MOTOR ROTOR CURRENT FREQUENCY Russian patent published in 2010 - IPC G01R23/00 

FIELD: electrical engineering.

SUBSTANCE: in steady-state operation of induction motor, instant consumed current of stator supply three phases are simultaneously. Stator current resultant vector magnitude is determined. Then discrete Fourier transformation of stator current resultant vector magnitude and one of stator currents are performed to derive gain-phase characteristics of resultant stator current vector and stator current magnitudes to select the main frequency component F_s0 of the stator current resultant magnitude in frequency range of 0 to 50 Hz and main maximum-amplitude component of stator currents with supply circuit frequency F_s to them to be used for determining rotor current frequency f_r=f_s-2·f_s0. Magnitude of stator current resultant vector is defined by expression where ia, ib, ic are instantaneous currents of stator windings.

EFFECT: higher accuracy of determination.

2 cl, 9 dwg, 1 tbl