A Beginner’s Guide to Online and Offline UPS Systems

24/06/2019

Uninterruptible power supply (UPS) can be a lifesaver in times or power failures, surges, spikes, brownouts or blackouts. It provides power to the systems for a temporary amount of time at the event of failure of the main supply. Power failures also put sensitive electrical equipment at risk in spite of modern solutions and alternatives developed to protect systems from damage caused by power surges, spikes, outages, electrical interference and brownouts.

Choosing the right UPS system to meet your needs and requirements can prove to be a task at first, but understanding how UPS works can help give you a clearer picture of which type will suit your needs. This post will give you the differences between online and offline UPS systems and how each one is useful to support different kinds of systems which is exactly what you require to make a decision on the type you need.

There are two main types of UPS systems, namely:

  • Online UPS Systems
  • Offline UPS Systems

Online UPS System

In the event of a power failure, an online UPS system provides an incessant and steady flow of current. The batteries are always connected to the inverter hence no power transfer switches are required. During a power failure, the rectifier drops out of the circuit and the batteries keep the power continuous. Conditional power is received here.

In an Online UPS, the power to be stored in the battery is first converted into DC and then converted into AC before reaching the load and this process is called "Double conversion". Online UPS System involves high cost and requires a large heat sink. Reliability is low compared to Offline UPS Systems. To understand more about working of the online UPS, check out this blog.

The prime advantage of an Online UPS system is that it puts up an electrical firewall between the incoming utility current and sensitive electrical equipment. The use of Online UPS systems is best in environments where electrical isolation is required or for equipment that is extremely sensitive to variation in power.

Offline UPS Systems

The Offline UPS Systems can only provide fundamental features, providing surge protection and battery sourced short term back-up power. The standby unit and its inverter are kept on offline mode until back-up power is required. It can also safeguard data sensitive equipment from surges, spikes and voltage variation and is the least expensive of the three types. Though it offers only the most basic services, an offline uninterrupted power source delivers back-up runtimes for a common consumer environment.

The shielded equipment is usually connected directly to incoming utility power. When the incoming voltage falls below or rises above a fixed level, the internal DC-AC inverter circuitry of the SPS which is sourced from an internal storage battery is turned on. The UPS then mechanically switches the connected equipment on to its DC-AC inverter output. Switch time average is 25 milliseconds, depending on the amount of time the UPS takes to detect lost voltage. The UPS will be designed to power equipment such as a personal computer without any blackout to that device. To know more about the working of the offline UPS, check out this blog.

In case of Offline UPS a small heat sink is required and its reliability is better compared to Online UPS Systems. Usually the offline UPS systems are more energy efficient & economical since they are cheaper and the constant load on the charger and the inverter is greatly reduced.

It is important to carefully consider multiple criteria according to your needs and assess before purchasing the UPS system that suits your need. Both types of systems have their own advantages and disadvantages but picking the one which best suits your needs is vital.

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