... coal mine well with mixed gas containing methane. In the power supply system of 50 Hz AC, ... phase losing, current leakage interlock, over voltage absorption, triphase imbalance;Real-time display triphase current, system voltage, operation status, loop on-line ... Control modesSingle motor-single speed,double motor-single speed,single motor-double speed,double motor-double speed,mixed usageTotal working ...