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 one phase is registered and subjected to discrete Fourier transformation to derive gain-phase characteristic of consumed current in said stator phase. At the same time, primary current component with supply circuit frequency f_c and maximum-amplitude side current components with low frequency f_L, smaller than that of supply circuit, and high frequency f_H, higher than that of supply circuit, are selected and amplitudes of current side components are compared. If aforesaid amplitude of low-frequency current exceeds that of high-frequency current, rotor current frequency is defined by the following expression, i.e. f_p=f_c-2·(f_c-f_H). If aforesaid amplitude of high-frequency current exceeds that of low-frequency current, rotor current frequency is defined by the following expression, i.e. f_p=f_c-2·(f_H-f_c).

EFFECT: higher accuracy of determination.

7 dwg, 2 tbl