EMC Optimization Of Explosion-proof Speed Control System By Frequency Variation

High power mine explosion-proof inverter has been widely used in the mine,because of its superior speed regulation performance. PWM modulation technology ismostly adopted in explosion-proof speed control system by frequency variation,which uses IGBT as the switching device. The high switching speed not only reducesthe switching loss, but also decreases the volume of the radiator. However, a lot ofdu/dt and di/dt will be produced in the process of IGBT opening and shutoff, leadingto very serious electromagnetic interference, due to parasitic capacitance and parasiticinductance in the circuit. With the improvement of power, electromagneticinterference is more and more serious. Electromagnetic interference probleminfluences the safe and stable operation of the system and becomes a significantproblem. Electromagnetic interference which is produced by explosion-proof inverterpollutes the grid environment. The high shaft voltage and shaft current will also affectthe working life of the motor. This paper analyzes the producing mechanism ofconducted interference, the prediction of conducted interference, the suppression ofconducted interference to explosion-proof speed control system by frequencyvariation.Analyzing the mechanism of conducted interference for explosion-proof speedcontrol system by frequency variation, the conducted interference is mainly due to therapid change of du/dt and di/dt in the transient process of IGBT and parasiticcapacitance, parasitic inductance. The path of the conducted interference is detailedlyanalyzed for explosion-proof speed control system by frequency variation.On the basis of the mathematical model of interference source, the highfrequency model of dc bus, the high frequency model of the cable, the high frequencymodel of asynchronous motor, the high frequency model of conducted interference isestablished for explosion-proof speed control system by frequency variation. Thesimulation for the high frequency model of conducted interference is taken in theexplosion-proof speed control system by frequency variation. Then, this paperanalyzes the influence to EMI for parasitic capacitance of busbar and IGBT, parasiticcapacitance of stator winding, common mode filter capacitance.EMI filter is designed for explosion-proof speed control system by frequencyvariation. EMI filter topology is determined on the basis of analyzing effect ofimpedance mismatching on EMI filter insertion loss, then establishing the high frequency model of conducted interference with EMI filter. Compared to spectrumsimulation diagram of conducted interference without EMI filter, the suppression ofEMI filter for conducted interference is proved. The conducted interference is wellsuppressed with EMI filter through the experiment of field test. Spectrum amplitudeof conducted interference is limited in the prescribed scope.