The Control Technology Of AC Apparatus' Phase Selection

In order to eliminate phenomenon of transient electromagnetism, AC apparatus such as AC relays, AC contacts and breakers must be disjuncted or closed according to special phase. Dynamic characteristic of AC apparatus on/off time is variable depend on phase. Now these functions are realized by electronic circuit and got used widely in phase selection devices. But there are still some problems in the aspects of economy and credibility, even if using CPU may bring the calculational problems.This paper mainly presents the technology of phase selection. It involves not only the detection of signal frequency, signal phase and power factor but also calculation and control of phase . The method of calculating phase is based on Fast Fourier Transform Algorithm (FFT). It is used to calculate signal frequency, signal phase, power factor and the phase on/off time according to sampling instantaneous value of voltage and current. This paper also introduces two aspects, one is the use of single-chip computer -Intel 16bit as key to realize signal collection, data processing and control of phase selection, the other is the communication of MCU and PC realized by Universal Serial Bus(USB).In addition, this paper also introduces and analyzes fuzzy comprehensive evaluation which is used in phase selection.The control technology of phase selection has been used on beaker's instantaneous characteristic test device for Jiang Su Chang Shu Switch Plant. The precision is ?? This technology is also applied on intelligent apparatus and high/low voltage switch device.