Power problems cause voice and data processing errors, hardware damage and expensive downtime. When an Uninterruptible Power Supply (UPS) as your power protection solution it is important to consider two elements:

How clean is my mains supply when it is present ?
Does the application need to be kept running when the mains fluctuates wildly or fails and if so for how long ?
Power Quality without battery back-up

Solutions vary in the power quality they provide and include:


A filter will attenuate spikes and electrical noise down to predefined levels. A very basic economic form of power protection.

Transient Voltage Surge Suppressors (TVSS)

A TVSS will clamp and divert the excess electrical energy of transients away from downstream loads. A TVSS is superior to a filter and can cope with lightning strike surges in some instances. They are commonly used within heavy industrial complexes and mobile base stations. When placed before Uninterruptible Power Supplies a TVSS will provide protection for the Uninterruptible Power Supply itself from local transient surges.

Voltage Stabilisers

Smooth out sags, surges and brownouts in an attempt to provide a near stable supply and are typically used in combination with a filter. They provide a form of power protection used typically in third world countries for non-critical loads such as fridges and freezers. A voltage stabiliser (also known as an Automatic Voltage Stabiliser or AVR) can be electronic or electro-mechanical.

Power Conditioners

The ultimate power protection without battery back up. They can be either transformer or electronic based and provide conditioning in the form of filtering, stabilisation and regulation. Some power conditioners can also provide Galvanic isolation. This is more commonly associated with Constant Voltage Transformers (CVTs).

Uninterruptible Power Supplies (UPS)

There are three generic UPS types. These differ in the power quality they can provide when the mains is present, the battery runtime they can provide, the type of output waveform they provide when running on mains and how smoothly or not they transfer between the mains and battery supplies:

  • On-line UPS (also known as double-conversion) - the ultimate power protection
  • Line Interactive UPS - intermediate level protection
  • Standby UPS - entry level protection

Whilst a generator will provide back up they use a fuel (normally diesel or liquid petroleum gas) supply rather than a sealed lead acid maintenance free battery. It is normally where an extended battery runtime set is not feasible to install a generator which can be supplied with a fuel tank sized up to or over 24 hours.