Development of a Zero-Flux Hall Current Sensor Dedicated for Large-Current Measurement of Superconducting Cable

Utilizing the fundamental concepts and distinctive traits of a zero-flux Hall current sensor, a digital driver circuit cored on DSP was designed, and the emphasis was introduced to a principle of a zero-flux Hall current sensor and an application of the sensor at 77 K. The sensor is used to measure an output current of the "linear-motor type" flux pump. The Hall current sensor and the control circuit are separated. The Hall current sensor operates at a low temperature of 77 K, and the control circuit operates at room temperature. Hall sensor is used to measure the magnetic field generated by the detected current and linearly output Hall signal. After linear amplification by analogous circuit, offset cancellation and proportional integral (PI) regulation, to proportionally generate a PWM signal by DSP for driving the full-bridge power amplifier. The output current from the power amplifier is then sent to the secondary winding of the magnetic ring to form a closed-loop secondary side compensation, so that the Hall device in the magnetic ring air gap is in a zero magnetic flux state, thereby improving the accuracy of high current detection. A maximum test current of 8 kA with an accuracy class of 1.0 has been achieved. The experimental results indicate the feasibility of the design, and the experimental data shows that the system of this sensor has advantages of precision and linearity.