The Design Of The Series Resonance AC Tester With Frequency-modulated

Due to high voltage of the electrical equipment in its normal operation,a large power supply capacity is required for its detection of withstand voltage value.This paper replaces the test method of traditional transformer boosting with the compensate inductances and electrical equipment( tested products) in resonance test circuits to obtain high voltage by the principle of the series resonance.The design of the series resonance AC tester with frequency-modulated reduces the power input capacity greatly. Its excellent output voltage waveform and easy operation make it used widely.Firstly, this paper introduces defects of the DC withstand voltage test in the detection of withstand voltage value for electric power equipment, and advantages of AC test in withstand voltage test of electric power equipment.Then it introduces technology principle and application of SPWM pulse width modulation in detail, and analyzes the concrete realization method of algorithm of SPWM wave based on DSP28335. Moreover, it has MATLAB simulation analysis for the series resonance test loop’s transfer function, determines the control method that locks the resonant frequency of the test circuit in the first and then regulates the output voltage. Meanwhile, it determines to regulate the output voltage by the double closed loop control strategy that adopts the output current of the inverter power supply as the inner ring and output voltage as the out ring,by detecting the phase difference of the tested product’s output voltage and test circuits’ input voltage to tracking system resonant frequency.According to the design requirements of the series resonance AC tester with frequency-modulated, it has designed the main control circuit of DSP28335 as the processing core, which is responsible for adjusting the frequency and amplitude of output voltage signal, collecting voltage current signal, data processing and communication, monitoring variables in the process of test and protecting in abnormal situation. It has designed the human-computer interaction circuit of STM32F103 as the processing core, which completes data communication with the main control circuit, modifies the test parameters, data query and print, liquid crystal display and other functions. At last, a prototype of the series resonance AC tester with frequency-modulated is developed. The experimental results show that the output voltage waveform of tester is good, and THD rate of waveform is small.The control method of tracing resonant frequency by the phase of hysteresis input voltage for the output voltage of tested product is stability, reliability, and precision, which meets the test requirements.