Types of UPS

UPS comes under different categories. The variety of UPS extends its use to domestic PC’s till industrial Computers. The role of UPS for industrial computers is much important as it needs to secure a complete network. The types of UPS are:

  • OFF-Line UPS
  • LINE – Interactive UPS
  • ON- Line Double Conversion UPS


These types of UPS are called differently as: Back-UP system, Stand by System, Inline UPS system.

In this type of UPS, the mains supply is send through a Filter and the output is taken out through a mechanical switch. The battery is continuously charged by the battery charger. ie, the battery charge is always maintained constant. This type of UPS holds a Detection circuit which frequently monitors current circulation from the main supply.

When the power supply from the mains goes OFF or, if the voltage in main supply fluctuates from its level above or below, then the inverter present inside the UPS starts to supply the voltage from the stored battery. The path of supply voltage – from mains, to battery – is switched over by the mechanical switch. The detection circuit takes very few seconds to detect the changes in supply voltage. This time delay between switch over is called as Transfer Time.

LINE – Interactive UPS:

These types of UPS use a completely different technique. This uses an Automatic Voltage Regulator (AVR) which automatically regulates (controls) the fluctuations in power supply.

It does not use the stored charge in battery under the conditions of emergency (ie at fluctuating time); instead it, automatically corrects the fluctuation. When the power supply completely cuts off, the battery comes into role.

The supply voltage below the required level is called “Brown-out”, and this low voltage is corrected by boosting up the voltage. The supply voltage passing above the required level is corrected by a method called as “Trim”.

Online Double-Conversion UPS:

It uses a principle called as Double-Conversion. According to this principle, the A.C supply from the mains is changed to D.C for storage. Again, this D.C is change to A.C and is given to the computer. So, the fluctuations in supply are completely abolished.

The inverter takes the supply from the charged battery, when the supply from the mains totally cut-off. This does not use any mechanical switching or detection methods. So, there is no wastage of transfer time.
But, the main disadvantages in this system are –

  • The voltage is transferred from A.C to D.C and again from D.C to A.C and so, the working capability reduces.
  • It is some ought costlier.

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