This is a type of UPS that supplies power to the AC load through the rectifier and inverter combo in normal operation and uses an inverter to supply AC power during a power failure. Therefore, the output power supply always stays ON and there is no transfer time.

This design offers the most consistent voltage and frequency to load with minimum variation and CHICAGO DIGITAL POWER offers 120 single phase from 1-3kW, 208 split phase from 6 to 20kW, 220-240 single phase from 1-20KW, three phase in 208 to 600 VAC from 15KW-2.2MW