The relay is suitable for using in the power circuits up to rated voltage 660V,rated current 500A 50Hz or 60Hz for overload and loss of phase protection of three phases iniduction motor and often combined with B series AC contactor into magnetic starter. T16 & T25 thermal relays have a friction trip operating mechanism with loss of phase running protection, pulback spring trip operating mechanism (jump mechanism ) with loss of phase protection for T85 & TSA45, backpack jump mechanism for T170 & T105,main circuit with instrument transformer jump mechanism with loss of phase for T250 & T370.