An uninterruptible power supply refers to an electrical device that enables a computer to run for a while longer whenever the mains power is lost. These devices also protect computers from electrical surges.
A UPS contains a battery such as an SWL3300FR, which “takes over” whenever the device detects power loss from the main source. Whenever an end user is working on a PC when the UPS detect the power loss, they have a chance to save the jobs they were working on and close the programs before the power from the battery’s power goes down. When the secondary power runs out as well, any data stored on the computer’s random access memory (RAM) is erased. Whenever there is a power surge, a UPS intercepts the surge and ensures it doesn’t damage your computer.
UPS in Data Centres
A UPS converts AC to DC by means of a rectifier and then converts it back to AC through an inverter. Flywheels or batteries store power for use in the case of a utility failure. A bypass circuit directs the power to the inverter and rectifier, running the load on incoming power or generator power.
Unlike a UPS, a generator does not seamlessly keep electronic devices running whenever the primary power is lost. Nevertheless, generators provide power for such devices for longer periods compared to UPS. A UPS does not provide power for long since it is powered by a battery.
While UPS systems are often referred to as double-conversation, standby, line-interactive systems, these names have been used inconsistently by different manufacturers. One system, however allows any of the three names – The International ElectroTechnical Commission (IEC), which adopted more technically descriptive terms in IEC Std. 62040.
UPS Types and Their Main Features
Voltage and Frequency Independent (VFI): voltage and frequency independent UPS systems are also called double or dual conversion since the incoming AC is rectified to charge the batteries and also drive the inverter. The inverter produces steady AC power to keep the electronic equipment running.
When power is lost, the batteries power the inverter, which keeps the load running. When power is back, either from the main supply or a generator, the rectifier drives a DC to the inverter, which recharges the batteries. The inverter runs full cycle. The power input and output are totally isolated, and the bypass is only used for maintenance safety or whenever an internal electronic fails. Since power is continuously supplied to the electronic equipment, vacuum fault interrupter is deemed the most powerful UPS type. Most UPS systems synchronise the output and input frequencies. However, that may not be necessary, and therefore still qualifies as frequency independent.
Pros and Cons of UPS Systems
Some of their advantages include:
- No delays in switching between the primary power source and the UPS.
- They can support delicate electronic systems better than generators.
- Depending on the power they need, users can choose the type and size of UPS.
- They are silent.
- Their maintenance costs are lower than those of generators.
Some downsides include:
- UPS can’t power heavy electrical appliances since they are run by batteries.
- Use of substandard batteries may lead to additional replacement costs.
- UPS systems often require professional installations.