Accurate Low-Speed and Torque Controls for Induction Motor With Secondary Current Feedback Using MI Sensor Installed in Shaft Hole

An accurate stationary low-speed and torque control system for induction motors (IM) with a secondary current (I₂) signal feedback loop is presented, in which a sensitive and stable micromagnetic (MI) sensor is set inside a drilled shaft hole to detect a slip frequency (sf) magnetic field proportional to an endring circular current. A finite impulse response digital low-pass filter (FIR-DLPF) is introduced to separate the I₂ signal from slightly higher frequency drive current I₁ signal at a low speed IM operation for such as the steel sheet rolling spread control. Accurate stationary low speed (45 r/min) control with error less than 1.11% and stationary torque (1.3 Nmiddotm at 45 r/min) control with error less than 0.76% for a 1.5 kW, 4-pole IM through 83 min operation were obtained, respectively