UPSs

A UPS, or uninterruptible power supply, is an electrical device that provides emergency power to a load when the input power source fails. In addition to supplying standby power, most UPS units also regulate voltage and protect against surges and waveform distortions, helping to prevent data corruption and equipment damage. They are widely used for computers, servers, networking equipment, medical devices, and industrial control systems.

UPS systems are categorized by delivery method: offline/standby, line-interactive, and double-conversion online. Offline units monitor input and switch to battery with minimal transfer time, offering basic protection. Line-interactive models add automatic voltage regulation to correct sags without using the battery. Online or double-conversion UPS continuously converts AC to DC to charge batteries and inverts back to clean AC, providing isolated, stable output at all times but with lower efficiency and higher cost. Larger facilities may use modular configurations that scale capacity.

A typical UPS consists of a battery bank, an inverter, a rectifier (charger), a transfer switch, and protection circuitry, often with a programmable outlet array and management software. Some units have hot-swappable batteries and remote diagnostics. Output is rated in VA and kW; runtime depends on load and battery capacity.

Battery technology has shifted from sealed lead-acid to lithium-ion in higher-end systems, offering longer life and lighter weight. Lifespans are typically 3–7 years for lead-acid and longer for lithium. Efficiency varies by design: online UPS often 90–98%; standby and line-interactive units commonly 95–99%. Regular maintenance and battery replacement are recommended.

Standards and safety: UPS devices comply with UL 1778, IEC 62040, and EN 62040. They require proper ventilation and surge protection. They bridge outages for short durations, not long-term power replacement.