In recent years, security of colliery receives social extensive concern more and more , a set of testing system which can test performances of synthetical protector is in need urgently. Therefore, a kind of phasen shift power has been designed in this paper. Among synthetical protector.testing system,in order to test synthetical protector devices which is based on short circuit protection,it is necessary to simulate zero preface voltage and zero preface current in the case of short circuit protection.It req...