Current imaging of three=phase rectifier-fed motor - is corrected by removal of signal component due to current transformer demagnetisation after phase current extinction

摘要

The three phase currents (IR,IS,IT) are measured by current transformers connected to respective operational amplifiers (1-3) with feedback resistances (R12,R22,R32). These circuits act as inverters or voltage followers according to the states of flip-flops (5-7) which are set (S) and reset (R) at different phases of the cycle. A summing amplifier (4) is followed by a diode (D6) which removes the falsifying antiphase signal component due to demagnetisation current. ADVANTAGE - Very accurate image of actual value of armature current is achieved with simple elimination of demagnetisation effect for optimal self-adjustment of current control.