How does AC & DC Current Work within a UPS?

By 29th January 2020Constant Learning

On January 29th 2020, the world will celebrate the 125th anniversary of Charles Steinmetz’s patent which transformed the use of electrical power across the world.

By devising a system of distribution via AC power, this German-born electrical engineer and scientist simplified the transformation process and made AC power accessible to all.

It’s thanks to his hard work and ingenuity that we have safe, reliable power that runs our computers, our servers, our televisions, our mobile phones, our washing machines and plays a vital role in our UPS systems.

Let’s take this opportunity to explore how AC and DC power work within a UPS system so you have a better understanding of UPS and how it can protect your power supply and support your business.

What is the difference between AC and DC current?

Before we get onto the finer details regarding UPS systems, let’s quickly recap what AC and DC currents are.

DC

DC stands for direct current. The electrons travel in a single direction like a river or stream and flow constantly. DC power is used in batteries and electronic equipment such as TVs, computers, radios and mobile phones. When you plug your electronic equipment into the AC power, your device converts it to DC and tends to supply around 3 volts (this can be higher).

AC

DC stands for alternating current. The flow of electrons changes direction at intervals of time known as frequency or times per second in the UK. Mains supply in the UK is AC. and runs at 230volts. We use AC because it’s easier to be converted to reduce losses when traveling long distances.

What are the components of a UPS system?

There are two main types of UPS systems; the offline UPS (VFD) and the online UPS (VFI).

The offline UPS uses a mains supply to charge a battery and feed the load. When there is a power spike or power outage, the power switches to the UPS battery within 25 milliseconds. As some modern equipment might notice this brief outage, the system is best used for non-critical equipment.

Then we have the online UPS. This is a more complicated system which ensures that the battery is always ready for use, even if there’s only a brief interruption to the power supply.

In this system, the AC power flows into a rectifier. The rectifier converts the AC power to DC and charges the UPS batteries. UPS rectifiers are resistant to electricity spikes and surges so don’t have to engage the batteries unnecessarily.

The inverter converts the DC to AC then powers the load as required, avoiding spikes, surges, and electrical noise and ensuring there’s no disruption in the power supply.

Summary: How do AC and DC work within a UPS?

To summarise, a UPS converts input AC power to DC in order to charge the backup battery and feed the Inverter. The inverter then converts this power back to AC and supplies the load.

When the power fails or there is a surge, spike, or other problem, the power can be taken from the battery by the Inverter which converts it back to AC. and used to ensure you can benefit from a seamless power supply.
Here at Constant Power Services, we offer a range of online UPS systems that can help safeguard your business from interruptions in the power supply.

Find out more about our range of solutions here.

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