Improvement Design of Underground Intrinsic Safety Type Pilot Circuit of Soft Starter

The paper introduced working principles and design of intrinsic safety type pilot circuit, and described basic principle of intrinsic safety type pilot circuit designed by relay isolated method, and indicated the circuit has problems of self starting and instable low-power. It introduced improved design of a pilot circuit controlled by photoelectric coupler isolation. The practical application showed that working current and the maximum short circuit current of the improved pilot circuit was less than the pilot circuit with relay control and has't inductor and capacitance, so its performance is more stable and action is more reliable.