GEAR FOR PROTECTION AGAINST VOLTAGE VARIATIONS Russian patent published in 1994 - IPC

FIELD: electrical engineering. SUBSTANCE: controlled voltage rectified in three-phase rectifier 1 which short-time jumps are delayed in ripple filter 2 is fed as bias voltage to first input of amplitude demodulator 3. High-frequency carrying oscillation from reference generator 4 goes to second input of modulator 3. Output signal of amplitude modulator 3 presenting sum of harmonic components goes to band-pass filters 6.1 and 6.2 tuned accordingly to frequencies of first and through coupling circuit 5 second harmonic components. Oscillations extracted by band-pass filters 6.1 and 6.2 are fed into proper detectors 7.1 and 7.2 which output voltages are supplied to inputs of voltage divider 8. Output voltage of divider 8 equal to ratio of amplitudes of first and second harmonics and proportional to controlled voltage is fed to inputs of threshold elements 9 and 10. Upper and lower threshold voltages of source 11 of reference voltages are fed correspondingly to second inputs of threshold elements 9 and 10. Outputs of threshold elements 9 and 10 are connected to inputs of actuating element 12. EFFECT: enhanced efficiency and reliability of protection. 3 dwg