Mumbai University > Electronics Engineering > Sem7 > Power Electronics 2

Marks: 10M

Advantages of Online UPS:

• It provides isolation between main supply and load.
• Since inverter is always ON, the quality of load voltage is free from distortion
• All the disturbances of supply such as blackout, brownouts, spikes etc are absent in the output.
• Voltage regulation is better
• Transfer time is practically zero since inverter is always ON.

Disadvantages of Online UPS:

• Overall efficiency of UPS is reduced since inverter is always ON.
• The wattage of the rectifier is increased since it has to supply power to inverter as well as charge battery
• Online UPS is costlier than other Uninterruptible Power Supply Systems.

Applications of Online UPS:

• Induction motor drives and similar other motor control applications.
• Intensive care units, medical equipments.

Advantages of Offline UPS:

• Offline UPS has high efficiencies, since charger is not continuously on.
• The power handling capacity of charger is reduced.
• Offline UPS are not very costly.
• Internal control is simpler in offline Uninterruptible Power Supply.

Disadvantage of Offline UPS:

• Since offline UPS provides mains supply when it is present, the output contains voltage spikes, brownouts, blackouts.

• There is finite transfer time from mains to inverter when mains supply fails.

• Output of offline Uninterruptible Power Supply is not perfectly reliable.

Applications of Offline UPS:

• Computers, printers, scanners etc use offline UPS.
• Emergency power supplies, EPABX.