102 26.02.2019

There are many new internet users who have been exposed to the web either through a mobile phone or a laptop. Inside of those gadgets, there are batteries which are charged through adapters with filters. These users are somehow protected from power supply variations, but for all the rest – desktop users, data centers, DNS servers and more, having a UPS is essential.

What is an UPS device?

UPS stand for uninterruptible power supply. It is a hardware device, that has different filters to stabilize the current and a battery that can provide power in case of current interruption. UPS devices are not made to replace the power supply, their purpose is to prevent devices from shutting off due to changes in the current; to provide the user with enough time to save their data before the battery dies or the user changes to an alternative power supply.

Power issues

The most common power issues are:

  • Too strong voltage
  • Voltage spikes
  • Too low voltage
  • Voltage dip
  • Noise
  • Not stable main frequency
  • Harmonic distortion

Depending on the type of UPS device, it will protect you from one or more of them.

Types of UPS devices

Standby UPS

This variation is the most basic one with the least amount of features. It has a battery backup and protects the device from surges. The protected device is connected to the normal power supply. In case of variations in the voltage, the standby UPS kicks in. It takes up to 25 milliseconds to switch to the battery of the UPS. The UPS inverts from DC to AC and delivers power. The working time of this UPS depends on the power consumption of the device and the battery capacity. If you want a UPS for your desktop, this type is the most popular.

Interactive UPS

The interactive UPS, also known as Line-interactive UPS, is one level better than the standby UPS. The biggest difference comes from the autotransformer, which automatically increases or decreases the output voltage. Thanks to this transformer, the UPS protects the device from continuous undervoltage or overvoltage without consuming battery power.

On-line UPS

This type of UPS has the batteries always connected to the inverter. No switches are necessary. If a power issue occurs, the rectifier disconnects the circuit and the batteries do all the work. When the power gets back to normal, the rectifier starts carrying most of the load again and the batteries start to charge. The on-line UPS is a kind of “electrical firewall” that separates the utility power and the device you want to protect. It can handle greater currents than the other two types and is usually used in large installations of 10kW and more.

UPS in data centers

We all know that the consumers want zero downtime. The UPS is critical for every data center. The type of the used UPS depends on the size of the data center.

Type of UPS Standby Interactive On-Line
Practical power range (kVA) 0 to 0.5 0.5 to 5 5 to 5000
Conditioning of the voltage Low Depends on the design High
Cost (per VA) Low Medium Medium
Efficiency Very Efficient Very Efficient Medium
Always on invertor No Depends on the design Yes