What are the main components of a UPS?

When your mains power is disrupted, a UPS will provide backup power to make sure your business isn’t negatively affected by a power disruption. In this article, we will be explaining the main components of a UPS system to highlight how it works when you’re in a power emergency.

The main components

Within a UPS system, you have your four main components: the rectifier/charger, the UPS battery, the inverter, and the static bypass switch. Let’s break down what the function of each of these is…


The rectifiers main function is to convert the input power from the mains from AC power to DC power, this is required to charge the UPS battery. This is then provided in a stable current directly to the inverter. The rectifier and charger can either be separate modules which are more common in smaller UPS systems (3Kva), otherwise, they will be a combined component.

UPS Battery

When the mains supply fails, the batteries in a UPS system will provide back-up power until the mains supply is restored. The runtime of your UPS is determined by the amount of battery power available which is measured in amp-hours.

Your UPS system will have at least one string of batteries, with the number of batteries required being dependent on the DC voltage of the UPS. The batteries within the string are connected, so if a single battery fails then the entire system will (which is what makes UPS maintenance so important!).

It’s important to remember that more batteries will provide more run time for your UPS, which is why many choose to add external battery packs (EBM’s) to increase the runtime of the system in a power emergency.


As mentioned earlier, the rectifier/charger will switch the AC voltage from the mains power supply to DC power – this is required to charge the UPS battery. For powering your systems and devices, you need AC power which is where the inverter comes in.

The inverter switches the DC power from the rectifier back to AC power. This conversion process of AC to DC and back to AC is essential as it smooths out any power disruptions such as surges to ensure the result is a pure sinewave.

Static Bypass Switch

Your UPS system is designed to be reliable in all instances, which includes the instance of a UPS fault. If there is a failure within your UPS system, the static bypass switch will automatically connect the load to the mains supply, so it will ‘bypass’ the rectifier, batteries and inverter. Although this power won’t be filtered (through the AC to DC to AC process we mentioned earlier), it will allow your equipment to continue functioning whilst the UPS fault is solved.

When it comes to choosing a UPS system for your business, Secure Power are here to help. As the UK’s leading UPS experts, we have the experience to make sure your business has the correct size for your needs that is both cost-efficient and effective.

If you want to discuss your needs, contact our experts here.

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