What Is An Uninterruptible Power Supply?

If you’re not too familiar with the topic of backup power protection, the question ‘What is an Uninterruptible Power Supply?’ will probably be the first thing that springs to mind when you initially hear the term mentioned. 

In answer to this question, an uninterruptible power supply, or UPS as it is more commonly known, is a device capable of providing a continual source of electricity in the event of mains failure or temporary loss in power.  

Should either of these situations occur, the UPS will provide an independent ‘no break’ supply, bridging the gap in electrical continuity to ensure that any connected equipment remains operational, until it can be either safely shut down or mains power is restored. 

UPS devices have the ability to provide power for anything from a few minutes to a few hours, depending on the electrical load they are required to support.  

The autonomy of each UPS being determined by the number and capacity of the batteries in the model and the energy consumption needs of any connected equipment or applications.  

In addition, UPS systems can also help to protect sensitive electronic equipment from damage caused by a range of power quality issues, such as interference, spikes, sags and surges. In these situations, the UPS will act like a filter, cleaning the output sine wave to guarantee power quality to any connected applications.    

What is an Uninterruptible Power Supply used for?

UPS systems are typically used to support mission-critical equipment and applications that rely on a clean and reliable power supply to operate. They can be used to protect anything from a single computer all the way through to an entire data centre.  

As such, they can be found supporting an assortment of processes across a diverse range of industries and sectors, including data centres, hospitals, office buildings, government, manufacturing, finance, retail, hospitality, IT, education and transport. Examples of their use can be found in almost any industry you can think of. 

How does an Uninterruptible Power Supply work?

A UPS will typically contain the following elements:  

• Rectifier/Charger – the rectifier, or charger, converts the Alternating Current (AC) electricity from the grid into Direct Current (DC) to charge the batteries or to feed the inverter 

• Inverter – the inverter converts the DC into AC so that it can be distributed to the equipment and applications connected to the UPS unit 

• Batteries – these provide the electrical energy that powers the UPS during a power anomaly or complete outage. Batteries will generally be either lithium-ion or lead-acid (VRLA) 

• Static and maintenance bypass – this is an electrical circuit that provides an alternative path for power to flow should the UPS fail or if it is overloaded  

• Control unit – the control unit is the smart element of the UPS that manages and coordinates all UPS functions via the unit’s software. These will include real-time system monitoring, switching between power sources and the regulation of output voltage and frequency  

Under normal conditions, electricity from the grid enters the UPS and passes through the rectifier, which converts the electricity from alternating current to direct current.  

Part of the electricity will be stored in the battery as DC, with the rest continuing through to the inverter, where it returns to AC to power the systems connected to the UPS.   

In the event of a temporary or complete power failure, where there is no electrical current available through the grid, the UPS inverter will immediately switch to battery mode and use the alternative DC voltage stored within its batteries. This ensures that the inverter output remains unaltered, thereby allowing the UPS to be able to provide a continual source of power.   

The length of time the batteries can power the UPS for (also known as the battery autonomy of the UPS), will depend on the capacity of the batteries and the energy consumption needs of any connected equipment or applications.  

When mains supply is restored, or an alternative power source such as a generator kicks in, the rectifier will resume its normal operation. 

What types of Uninterruptible Power Supply systems are there?

There are three main types of UPS systems; offline (or standby) UPS, line-interactive UPS and online double conversion UPS.  

Below is an outline of their key differences:  

Offline (or Standby) UPS  

The simplest and most affordable system, an offline UPS provides basic protection against power outages and anomalies. Battery autonomy will typically last for just a few minutes therefore this type of UPS is more suitable for protecting workstations, terminals and basic electronic equipment below 1kVA.  

Line-Interactive UPS 

Line-interactive UPS provide a higher level of protection than an offline, or standby unit, and have the ability to protect you both on and offline. These UPS use an automatic voltage regulator (AVR) to correct any abnormal voltages without the need to switch to battery mode. When the voltage crosses over a preset low or high threshold, a line-interactive UPS will use transformers to either increase or reduce the voltage by a set amount to return it to within an acceptable range.   

Line-interactive UPS are typically used in smaller, less critical applications such as PC’s, non-critical networking equipment, entry-level servers, telephone systems and small motor loads up to 3kVA. 

Online double conversion UPS  

Online double conversion UPS offer premium power protection for critical and sensitive equipment.  

These systems provide all of the usual security afforded against power outages and anomalies yet also have the ability to regulate the level of power delivered to any connected equipment. Sophisticated double conversion technology ensures that output voltage and frequency are completely isolated from the input voltage and frequency (often referred to as voltage and frequency independent).  

This isolates the critical load from virtually all types of power problems making the online double conversion UPS ideally suited to supporting secure IT and server networks, data centres, telecoms systems and vital hospital technology. 

Think of an Uninterruptible Power Supply as an insurance policy ….  

The question ‘What is an uninterruptible power supply?’ will hopefully have been answered in this blog, together with a few others you may have had regarding how they work, the industries they can be used in and the key differences between the three main types of UPS.  

Regardless of whether the devices are used to support a small business or larger scale operation, UPS systems act as an insurance policy – safeguarding essential equipment and applications from the major issues that can be caused by unpredictable power anomalies or complete mains failure. 

If you would like further information on a power protection strategy for your organisation or simply wish for advice on the best type of UPS to support your mission-critical equipment, please contact a member of the team on 01246 431431 or email info@powercontrol.co.uk