... in online sine wave made with isolating output transformer, input under - voltage, over - voltage protection , output under-voltage,over -voltage, over load ... Control modeSPWMOutput waveformSine wave, THD <3%Output voltage accuracy220V± 1.5%Output frequency50Hz/60Hz± 0.5%Output transient response±4% (100% load varies ... , relative humidity: 95%(no condensation) UPS Low Frequency online type,single phase