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 a universal multi-purpose socket and current display.Effectively protect high-performance thyristors from overvoltage and voltage limits with multiple protection Note 1: The 4000W mentioned above refers to the maximum power when working under ohmic loads.The power under inductive load is 1/3 of the ohmic load.The ohmic 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.