What are the main components of a UPS system?

A UPS (Uninterruptible Power Supply) system typically consists of several main components that work together to provide backup power during electrical outages or disruptions. The main components of a UPS system are as follows:

UPS Rectifier  

The UPS rectifier carries out several key functions. The first is to convert the incoming AC (alternating current) power from the utility source into DC (direct current) power. And the second main function is to charge the batteries of the UPS. It ensures that the batteries are maintained at full charge and ready to supply power when needed.

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

 
UPS rectifiers can accept wide input voltage fluctuations, meaning the system can handle overloads or surges without having to engage the batteries.  

UPS Batteries 

UPS systems rely on batteries to store electrical energy. The batteries are usually sealed lead-acid, lithium-ion, or similar types of rechargeable batteries. They provide power to the connected equipment during power outages or fluctuations.

UPS battery systems have at least one string of batteries, with the number of batteries required depending on the DC voltage of the UPS. Batteries within a string are connected in series, so if a single battery fails, so too does the entire string.  

For smaller UPS systems, the batteries are often internal to the unit. Whereas in larger solutions, UPS batteries are often housed in their own standalone cabinets.

UPS Inverter 

The inverter is responsible for converting the DC power from the batteries back into AC power. It supplies clean and stable AC power to the connected devices, mirroring the utility power characteristics.

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

Static Bypass Switch 

This component acts as a bridge between the utility power and the inverter. It monitors the quality of the incoming utility power and, in the event of a power failure or voltage anomaly, swiftly transfers the load from the utility power to the inverter power, ensuring uninterrupted power supply. 

Having to transfer to mains supply isn’t ideal as the power won’t be filtered or conditioned as is usually the case with an online double-conversion UPS, but it does enable equipment to continue functioning while the UPS is repaired or replaced.  

Bypass Switch

The bypass switch provides an alternative path for the electrical load, allowing it to bypass the UPS system entirely and be powered directly by the utility source. This switch is useful during maintenance or repair of the UPS system, or in case of a fault.

Monitoring and Control System

UPS systems often include a monitoring and control system that provides information about the status of the UPS and the connected load. It can offer features such as battery monitoring, voltage regulation, load balancing, and remote management capabilities.

Cooling and Ventilation

UPS systems generate heat during operation, and therefore, they incorporate cooling fans or other cooling mechanisms to prevent overheating and ensure optimal performance.

Display Panel

Many UPS systems have a display panel or an interface that allows users to monitor the status of the system, battery charge level, input/output voltage, load levels, and other relevant information.

Protective Devices

UPS systems often include protective devices like surge suppressors and voltage regulators to safeguard connected equipment against power spikes, surges, and voltage fluctuations.

These components work together to provide uninterrupted power supply, protect against power disturbances, and maintain the stability and reliability of connected equipment. The specific configuration and features of a UPS system may vary depending on the capacity, application, and intended use of the system.