Study On EMC Of The Electric Speed Control System For Flame-proof Integrative Variable-frequency Motor

The compact and excellent explosion-proof motor is one of the preconditions for the manufactural demand of the high-power, high-strength and low-airframe combination cutting and loading machines for meeting the thin coal seam mechanical mining demand. The flame-proof integrative motor that are made of frequency-converter and motor in a protecting shell provide a self-contained drive system, and meet the manufactural requirements of the mining machinery. But the EMI affects the safety and stabilization of the surrounding equipments and the motor system itself. The frequency converter is the primary EMI source. So study on EMC strategy in mine converter is especially important. Starting with the 3 factors of EMI, combining with the making work of frequency converter in integrative motor system, the EMI source, preventive measure, EMC risk evaluation and simulation of EMI are researched in this paper. The main contents and innovations include:(1) EMI simulation analysis is carried on the switched-mode power supply of frequency converter. The result of simulation and debugging testify that the supply satisfy the pertinent criterions on emission limit basically.(2) The output voltage of IGBT inverter bridge arm can be regard as the EMI source. According to analyzing the reason for the formation of EMI and propagation characteristic, the suppression method is presented by breakage EMC coupling path. Theory analysis adopts the simulation of surface current and electrical field of heat sink.(3) According to the surge immunity test to main circuit, validate the product whether satisfy extreme circumstance. A small and finer-EMC snubber circuit is designed with virtual prototyping technology, based on the manufacturing need of the sink coal mine machines.(4) For the aim to advance the immunity of control circuit, according to the electrical fast transient burst immunity test by the switching power port, adopt corresponding ameliorative measure to acquire some suppressive effects. (5) EMC theory as the guide, combining the configuration analysis, to supply the scheme and idea of system-level EMC analysis with 3D modeling technology. During the manufacture of mine-used converter prototype, based on the compact volume characteristics of the mine-used motor driver, the terrace generatrix is designed, from view of creepage distance, mechanism intensity, low stray inductance bus bar, and EMC. The conclusion is that the terrace generatrix is propitious to reduce the power generatrix parasitical reduction, decrease the additional high voltage during the switching process, cut down the electric interference in the motor driver and ensure the system safe operation,which is proved by engineering calculation and computer simulation respectively...