Research for accurate control of induction motors using amorphous core field sensors

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1. Detections of secondary current and electric torque of induction motors using amorphous microcore field sensors: The robust field sensor was constituted using amorphous microcore field sensors: The robust sensor was constituted using an amorphous core multivibrator with a negative feedback. Stable current detection was done for the core temperature variation of - 200 ゜C to 200 ゜C. Stable detection of the secondary current (I_2) of a squirrel-cage induction motor (IM) was carried out setting the 8 pairs of amorphous cores around two endrings. Ripple-less torque detection was done multiplying two phase I_2 by two phase main flux. Basis of construction of accurate vector control systems for IM with torque feedback loops was established.2. Detections of the slip frequency and the secondary current of IM using a shaft core field sensor: Accurate slip frequency vector control systems require direct detections of the slip frequency (sf) and I_2. These were stably detected constituting a field sensor using a magnetic multivibrator with two coils set around a IM shaft.3. Sinusoidal magnetic encoder: Accurate ac servomotors require accurate detection of the rotor position using a high-performance encoder. A new magnetic encoder was constituted using 100 pairs of amorphous microcores set around a 100-pole ring magnet. 1 million pulses for one rotation of the magnet is possible due to cancellations of irregular distribution of field strength at each pole, influence of the off-center motion of the shaft, and external disturbance fields in the starshaped amorphous core group.