Fluxgate Based B Type Residual Current Sensor Design

In recent years,with the innovation and development of switching devices,the residual current waveform becomes more and more complex,and gradually develops to high frequency,which brings greater challenges to the residual current detection technology.Traditional AC residual current protector can only detect low-frequency AC,while type A protector can detect low-frequency AC and pulsating DC.Facing the trend of high-frequency residual current,both of them can no longer meet the requirements of power system protection,so type B protector emerges as the times require.In the noncontact weak current detection,fluxgate technology has gradually become a mainstream scheme due to its high resolution,high stability and wide detection frequency band.This paper compares many current detection methods and their principles,selects fluxgate current detection,studies the principle of fluxgate current detection,analyzes the advantages and disadvantages of voltage excitation and current excitation fluxgate current detection methods,combined with the design requirements,selects the voltage excitation as the final scheme,and establishes the fluxgate current sensor probe with voltage excitation The influence of residual current on the output of the sensor is obtained.A Co based amorphous alloy magnetic ring vitrovac 6025 z is used as the magnetic core,and the probe structure of the sensor is designed.The square wave with the frequency of 1.5 kHz from 0 to 10 V is selected as the excitation.Using stm32f103rct6 as the controller chip,the hardware circuit of providing excitation signal,signal conditioning and detection for the sensor probe is designed,and the software program of single chip microcomputer is compiled to control the sensor closed-loop to ensure the stability of the sensor.Compared with the traditional current detection chip,the current detection algorithm can detect the high frequency components of residual current more accurately.The designed residual current sensor works well.It can detect and alarm DC component above 6 mA and any waveform RMS below 1 kHz and 30 mA.It has self calibration function and can correct its own error.The system works stably and has certain practical value.