Online UPS

It first rectifies incoming AC to DC, which charges the battery and feeds an inverter, and the inverter then creates a fresh AC output. Because the load is always powered by the inverter, there is no switching when mains fails, and voltage and frequency stay stable. Most units also offer a bypass path for overload or fault conditions.

A modular UPS is built from hot-swappable power modules in a common frame, so capacity can grow by adding modules and a failed module can be replaced without shutting down the load. It suits data centres and growing facilities. The upfront cost may be higher, but the flexibility and repair time can justify it.

Total the load in kW, divide by the UPS power factor to get kVA if needed, add 20 to 25 percent margin for growth and avoid running above about 80 percent loading. Then decide runtime to size batteries. Check inrush and generator compatibility. For critical systems, ask an engineer to review.

Modern UPS often have an output power factor near 0.9 to 1.0, so a 10 kVA unit can supply 9 to 10 kW, whereas older ones with 0.8 could supply only 8 kW. Always compare ratings in kW. The input power factor and harmonic distortion also matter when a generator is the backup source.

A lift UPS supplies the lift controller and drive with power during a mains failure, so the car can reach the nearest floor and the doors can open, instead of trapping passengers. It is sized for the lift motor load, usually for a short time. Check the lift manufacturer's requirements before selection.