Uninterruptible power supplies

An off-line Uninterruptible Power Supply (UPS) is designed to back up the supply to electrical loads using energy stored beforehand in batteries. The nominal voltage of the external battery bank is 240 V (20 × 12 V) or 360 V (30 × 12 V). Charger rated (10…30) A.

A UPS is required where the supply voltage in the network goes outside permissible limits. A UPS provides fault-free power to the load and protects computers and other industrial and domestic equipment rated 220/380 V AC at 50 Hz, up to 50 kVA for three-phase loads and up to 17 kVA per phase for single-phase loads.

An off-line UPS with a high-speed thyristor static transfer switch, a built-in charger and an external battery bank provides:
- short transfer time;
- minimal conversion losses;
- low heat dissipation;
- silent operation;
- the ability to run for long periods (run time depends on the capacity of the external battery bank) without starting an external diesel generator.

The UPS has an output for starting an external generator set automatically; an automatic contactor bypass circuit is available as an option.

When running from batteries, the UPS supplies the load with three-phase sinusoidal AC at 50 Hz.

The UPS monitors the state of the battery and the mains and indicates input and output status.