Offline UPS - low frequency transformer
Offline (standby) UPS is mainly used for Small Office and Home Office, also called SOHO. Offline UPS is usually between 0 and 10 kVA. This solution covers mainly power discrete solutions and is usually divided into low frequency and high-frequency transformer-based systems. It is used when AC line voltage is present a relay bypasses the inverter, which remains off. The battery charger operates to maintain full charge. If the AC power fails the relay switches, the UPS output over to the inverter, which starts up after a short interruption of 10-20 ms to supply backup power.
- 50/60 Hz iron core transformers which are large and heavy
- Sine or square wave output voltage
- Full-bridge or push-pull inverter/charger while full-bridge topology is mainly used
- Robust against AC line surges