Online UPS

ON-line UPS (Inverter-preferred):

We have complete range of Online UPS and also we can explain the process of UPS system.

Here it shows the block diagram of the on-line UPS system. In this mode of operation, the load is always connected to the inverter though the UPS static switch. The UPS static switch is a normally 'ON' switch. It turns-off only when the UPS system fails. In the case the 'Mains Static Off' switch and used only when UPS is to be bypassed. The various operation modes are:

General block diagram of Online UPS system
MODE 1: When the AC mains is ON, the rectifier circuit will supply the power to the inverter as well as to the battery. Therefore, it acts as a rectifier cum charger. Hence, its ratings are usually higher. The inverter output is connected to the load via UPS Static Switch. Battery will be charged in this mode.

MODE 2: If the supply power fails suddenly, the rectifier output will be zero and hence the battery-bank now supplies power to the inverter without any interruption and delay. There will not be any change in inverter as well as the load. After restoration of the line supply, the charger supplies the inverter and recharges the battery automatically first in constant current mode and then in constant potential mode. Various rates of battery recharge may be set depending upon the application. The inverter has to be designed carefully because it supplies the load continuously. There should not be frequency failure of the inverter-system.

MODE 3: In case if the UPS fails(inverter fails), then the normally "OFF" mains static switch is turned-on which automatically transfers the A.C. line to the load in less than ¼ cycle period with no phase discontinuity. This not only maintains power to the load, but also actuates the failure alarm signal to draw attention of the attendant. This type of system is more popular because it can provide full isolation of the critical load from the a.c. line and also provide power conditioning. Also, the mode of operation does not charge during the failure of power.

Its changeover time is very less (theoretically zero) and there is no interruption during transfer from line to battery and vice versa.
This system protects the critical load against surges, spikes, line noise, frequency and voltage variation, brownout and outages. All these protections are not available in the off line system.