... ,wharf,enterprise,tunnel,etc.It is mainly used in power supply occasions of AC 50-60HZ and ... chemical deposition,dust or dirt that will affect transformers insulation seriously,also explosive or corrosive medium is ... wharf, enterprise, tunnel, etc. It is mainly used in power supply occasions of AC 50~60Hz and voltage less ... 1min under two times of rated current power transformers provider 220v to 380v