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How does a UPS (Uninterruptible Power Supply) work?

In simplest terms, an uninterruptible power supply (or UPS) is a device intended to prevent a loss of power that could cause damage or disruption to an electrical system. Essentially, it’s a backup battery in the event your mains supply has a problem and it can make sure critical systems stay active long enough to shut down – if you need prolonged power in the event of a disruption, you’d be best off looking at a generator as a UPS will protect you for only a few minutes.

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How does the flow of power work?

To help explain, we have a video discussing what a UPS does to prevent loss of power.

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What does a UPS protect against?

There are four main problems that can befall your electrical supply, all of which can be safeguarded against by proper use a UPS system. These are

  • Power Surges – A sudden increase in power flowing through to your device is typically caused by something like a lightning strike. This leads to a sudden increase in power followed by a drop which causes damage to equipment.
  • Overvoltage – Overvoltage is when the power being supplied is greater than the power required and can cause overheating and damage. Unlike with a power surge, this power is over a sustained period and causes different problems.
  • Undervoltage – Also known as a ‘brown-out’, Undervoltage is what occurs when the power supplied is less than is required. This could be from a sudden demand for power in other areas or a problem with the grid, the lack of flow leads to damage and active data loss.
  • Power Outage – A complete disruption of power, either short or long term. There can be a number of reasons that you might be subject to a power outage but the results can be severe with data loss and system downtime being the major contributors.

By providing a constant flow of power, a UPS allows you to handle these problems as they arise. UPS systems moderate the flow of power and jump in with charged batteries in the event of total disruption.

What are the parts of a UPS?

A UPS consists of four primary parts which, when working together, provide you a steady flow of power in the event of an emergency. They will likely be arranged in different formations depending on what version of a UPS you have available. An ‘online double conversion UPS’ will have a different layout than an ‘offline UPS’, but both machine types consist of these four main elements.

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  • The Charger – Also referred to as the Rectifier, this is used to ensure your batteries remain charged while they’re waiting to be activated. In order to do this, the incoming AC (alternating current) needs to be converted into DC (direct current) and it travels in this form through the majority of the UPS. The charger will be set-up differently if it’s for an offline or online UPS as the flow of power will be different.
  • The Battery – This is the heart of any UPS system; the batteries are how you store the power that you need to use when the power is disrupted. The batteries involved are stored in long ‘strings’ with several connected in series for continuous power. The danger here is that if one battery fails, the entire string will and highlights the importance of frequent battery testing. The charger is used to ensure the power of the batteries remains as high as possible.
  • The Inverter– The second half of any double conversion process and a vital element in turning your stored battery power into usable electricity. The inverter is one of the core differences in your UPS set-up, for an online UPS the inverter is constantly active and in use for a seamless change over to batteries while in an offline UPS the inverter has to be activated by a bypass switch in the event of power problems. The inverter also helps to ensure the power output is consistent, stable and modulated.
  • The Switch – We have the initial three stages of charger (converts incoming AC into DC), the batteries (charged by DC) and the inverter (converts back to AC from DC) but there’s one core element of the exchange we haven’t yet discussed and that’s the switch, though what form this switch takes will differ depending on what form of UPS you’re using. For an offline and line-interactive UPS, the switch will trigger as soon as the power is disrupted from the mains, activate the inverter and flip over to the battery supply. In an online UPS, as the power is already flowing through the inverter at all times, the switch is a bypass switch and is set-up to trigger in the event of a UPS failure by diverting over to a separate circuit for the mains power.

With these four parts working in tandem, your UPS can ensure that when you have a sudden disruption you can still have access to power.

You can find our UPS Buying Guide here.

If you’re looking to buy a UPS,  get in touch with our sales and engineering team  who can advise you on which style of UPS best suits your needs.

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