Protection System Design of Overload , Short Circuit and Three-phase Imbalance for Electromagnetic Starter in Coal Mine

摘要

An intelligent protection system of electromagnetic starter in coal mine was designed. Its controller core is PLC LM3108K. The voltage rank of protection system is 660V and the electric current rank is 400A. It has protection functions for overload, short circuit, break phase and three-phase imbalance. The system achieved overload protection by using the method of inversing time overload. Greater the overcurrent is, Shorter the time of protective action is. The system achieved short circuit protection by using phase-sensitive protection method, which improves sensitivity and reliability of short circuit protection. The system can display work status parameters and fault types timely by text LCD. It has the advantages of hardware circuit structure flexibility and automatically reset after fault relieved.