What are the main components of a UPS power supply, accepting wide input voltage

Any online double-conversion uninterruptible power supply (UPS) system has four main components: rectifier; UPS battery; inverter; and static bypass switch.

UPS Rectifier

The UPS rectifier performs several key functions. The first is to convert input power from AC (alternating current) to DC (direct current). Its second main role is to charge the battery, while the DC power is also routed to the inverter.

Depending on the size of the UPS, the rectifier module may include a battery charger. For smaller UPS systems (i.e., below 3 kVA), it is not uncommon for the rectifier and battery charger to be separate components.

The UPS rectifier can accept wide input voltage fluctuations, which means the system can handle overloads or surges without engaging the battery.

UPS Battery

When the main power fails, the battery in the UPS system provides emergency power. The rectifier or a separate charger ensures the battery is always charged.

A UPS battery system has at least one string of batteries, and the number of batteries required depends on the DC voltage of the UPS. The batteries in the string are connected in series, so if a single battery fails, the entire string fails.

For smaller UPS systems, batteries are typically located inside the unit. In larger solutions, UPS batteries are usually installed in their own separate cabinets.

UPS Inverter

This component completes the second half of the double conversion by switching the DC voltage from the rectifier or battery back to AC output that powers critical loads.

This conversion process (AC to DC to AC) and filtering eliminates events such as spikes, sags, surges, and electrical noise, ensuring the final output is a pure sine wave.

Static Bypass Switch

This component provides protection in the event of a UPS system failure. In the event of a UPS failure, the static bypass switch automatically connects the load to utility power, bypassing the rectifier, battery, and inverter.

Having to transfer to mains power is not ideal because the power is not filtered or regulated as it typically is with an online double-conversion UPS, but it does allow equipment to continue running while the UPS is being serviced or replaced.

Other UPS Components

Depending on the size and type of UPS, several other common components may also be included, such as fans or capacitors.

In addition, there are components such as external maintenance bypass, which allows the UPS to be removed and/or replaced without interrupting the load, transient voltage surge suppressors (TVSS), and monitoring and communication applications that comply with Simple Network Management Protocol (SNMP).