Speaking of computers, there is a noise in the electronics world about a little black box called the uninterruptible power supply! I bet you heard this device before and have a glimpse of what it can do.
[Read: Go up for UPS! ]
Basically UPS protects electronic devices connected to it from brownouts and power surges. Also it serves as a power giver to the units for us to properly shut them down to prevent data loss.
[See: Uninterruptible Power Supply: Perfect device to save your business! ]
There are two UPS technologies that dominate in the market – “on-line” and “off-line” types. The description “on-line/off-line” simply indicates whether the inverter (part of the UPS that converts DC provided by the batteries to the AC that we use from wall socket) is on-line or off-line during normal use. Let’s take a close look at the two types to learn them better.
OFF-LINE UPS
This is the simplest form of UPS system. Referring this system as a UPS is not connected because the inverter is normally off. For this reason, off-line UPS are also known as standby power sources.
Advantages
- Lower cost than others
- Under mains power unit charge batteries and power passes directly to the load
- During mains failure, batteries provide power to DC/AC inverter to provide 220VAC power to the load.
- High efficiency, since charger is not continuously on
- Power handling capacity of the charger is reduced.
- Internal Control is simpler
Disadvantages
- Since offline unit provides mains supply when it is present, the output contains voltage spikes.
- There is finite transfer time from mains to inverter when mains supply fails
- Output of off-line units is not perfectly reliable
Applications
Computers, Printers, Scanners, Emergency Power Supplies, EPABX
ON-LINE UPS
The on-line UPS systems have much more complex designs than Off-line systems, while the price, weight and volume are higher. The inverter of an online types supplies continuous power to the critical load. Under conditions of overloads, the static bypass switch provides mains power to the load. This kind of UPS prevents the load from surge voltage, transient voltage, noise and brownouts.
Advantages
- Constant duty inverter
- Design inherently improves power quality and reliability
- No break
- Static bypass improves reliability
- Provides isolation between main supply and load
- Since inverter is always ON, the quality of load voltage is free from distortion.
- All the disturbance of supply such as blackout, brownout, spike are absent in the output
- Voltage regulation is better
- Transfer time is practically zero since inverter is always ON
Disadvantages
- Overall efficiency of UPS is reduced since inverter is always on
- The wattage of the rectifier increased since it has to supply power to the inverter as well as charge battery
- On-line UPS is costlier
Application
- Induction motor drives and similar other motor control applications
- Intensive care units and medical equipment
This is the tale of the tape, a head to head comparison between the two UPS systems. Use wisely your UPS, know what type you need to save money, time and energy. Thanks for reading.
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