... and fixed three position switch for frequency settings4) IGBT / PWM circuit5) High load and frequency stability6) ... labs3) For others which need frequency conversion power supplyTechnical characteristics: Output power500VA200KVACircuit modeIGBT/PWM inverter ... .5%(impedance load)Response time2msRead outputVoltage , Current, Power, Frequency, LED digitalProtections functionOver voltage, over load, ...