: Use high performance SCR as internal chip. Thickening metal shell, high temperature resistant and durable in use. Leistung Perfect Performance: Stepless voltage adjustment with rotary knob, zero hysteresis, zero delay, fast response. The AC voltage regulator cover is equipped with universal multi-purpose socket and current display. Effectively protect high-performance thyristors against overvoltage and voltage limits with multiple protection Note 1: The 4000W mentioned above refers to the maximum power when working under resistive loads. Power under inductive load is 1/3 of resistive load. The resistive load concerns Wolframlampt Diew. on line excitation motor and more. Electronic products with circuit boards should be used with caution. Note 2: The measured output voltage is a virtual voltage if there is no load. It must be connected to a load of 20W or more to measure the correct output voltage. The output is a Wehtselstrom metal shell and must be safely grounded.