Difference Between Online UPS and OffLine UPS

Difference Between Online UPS and OffLine UPS

Difference Between Online UPS and OffLine UPS

What is an UPS? UPS, Uninterruptible Power Supply is a device that supplies power in case of power failures. A UPS can be either Online UPS or Offline UPS. Both types of UPS can be used as a backup power source but there are many differences between them.

Data Secure is become more important for whole world, UPS systems, Gives emergency power to a system if the grid is shut down, UPS are becoming an essential part of our lives. From the base structure, All UPS are categorized into two types: Online UPS and Offline UPS.

What online UPS? The Online UPS is a type of UPS that supplies power to the AC load through the Rectifier and Inverter Combo in normal operation and uses an inverter to supply AC power during a power failure. Therefore, the output power supply always stays ON and there is no need for switching. Hence, there is no time delay in switching between its sources. There is no interruption in the case of power failure even for a nanosecond.

What Offline UPS? The offline UPS is a type of UPS that directly supplies the power to the AC load from the AC mains in normal operation and uses an inverter to power the AC load from the DC battery. Since there are two separate lines of supplies, the output supply must be switched between the two sources.

The switching speed of an Offline UPS is around 5ms which is enough to keep a computer from shutting down. But not fast enough to keep a smooth operation of sensitive equipment in hospitals.

What is the difference between online UPS and offline UPS?

Here is is brief introduction to answer your questions about:

Operation difference:

The batteries of offline UPS are charged all the time. If the power fails, the load is powered by the inverter. Lower Cost offline UPS generally, when on inverter/battery backup, provide a square/pseudo sine wave output waveform.

Online UPS takes the incoming AC mains supply and converts it to DC which feeds the battery and the load via the inverter. If the mains supply fails, then the batteries feed the load via the inverter with no interruption to the output supply at all. It means our electronics get power from the online UPS, rather than directly from the AC mains. Therefore, even if the main AC power fails, the operation of our electronic equipment does not need to be stopped.

What’s more, The dual conversion design (AC-DC / DC- AC) of an Online system ensures a far higher degree of isolation of the load from the irregularities on the mains supply. That’s why the Online system delivers a fixed and stable output all the time.

Voltage distortion difference:

Online UPS: Voltage distortion does not reduce the performance.

Offline UPS: The more the voltage fluctuations, the more the offline UPS is used. A frequent switch could lead to switching delays or could ultimately reduce its performance.

Price difference：

Compared with online UPS price，offline UPS’s are cheaper.

ONLINE UPS

OFFLINE UPS

The UPS that supplies power from the AC mains to the load through the rectifier and inverter combination The UPS that supply the AC mains power directly to the load. It continuously draws current from the battery. It only draws current from the battery during primary source failure or power outage. It requires a large battery charger circuit because it carries the entire load current. It requires a small charger circuit because it only charges the battery. The input supply and the load is completely isolated. There is no isolation between the input supply and load. It has high-performance output because it protects the output load from input voltage spike and distortion. Its performance reduces with the input voltage distortion; which is directly connected to the load. There is not switching between the source, hence no time delay It uses a static transfer switch to switch between its source with a time delay of 5ms It stays ON almost at all times. It turns ON only at power failure. Due to its continuous ON condition, it is inefficient and unreliable. It is more efficient and reliable because it mostly stays off. It requires large heat sinks because of the high operating temperature It requires smaller heat sinks because of low operating temperature due to its off state mostly. The components used must have the tolerance to withstand high temperature There is no need for the components to have high-temperature tolerance. It is expensive than Offline UPS. It is cheaper than Online UPS. It is used for very sensitive electronics that cannot tolerate any gap between supplies such as in-hospital ICUs Offline UPS is used for electronic equipment that can tolerate a delay of 5ms such as Computer etc

How to Select: Inline UPS or Offline UPS?

In situations where a square/pseudo sine output waveform is not acceptable then true sine wave more expensive off-line or online UPS are recommended. But when you are much concerned about the cost and wish a lower operating temperature, offline UPS is better.