How UPS systems works?

A UPS solution provides voltage that is:

1. Free of all disturbances present in utility power and in compliance with the strict tolerances required by loads.

2. Available in the event of a utility outage, within specified tolerances


UPS systems satisfy requirements in 1 & 2 above in terms of power availability and quality by:

1. Supplying loads with voltage complying with strict tolerances, through use of an inverter.

2. Providing an autonomous alternate source, through use of a battery.

3. Stepping in to replace utility power with no transfer time, i.e. without any interruption in the supply of power to the load, through use of a static switch.


These characteristics make UPS units the ideal power supply for all sensitive applications because they ensure power quality and availability, whatever the state of utility power.


The four components of a UPS System

1. Rectifier/charger: The rectifier carries out several key functions. The first is to convert the input power from AC (Alternating Current) to DC (Direct Current). It also recharges the batteries, while the DC power routes to the inverter too.

2. Inverter: which produces quality electrical power free of all utility-power disturbances, notably           micro-outages and that is within tolerances compatible with the requirements of sensitive                     electronic devices.

3. Battery: which provides sufficient backup time to ensure the safety of life and property by                   replacing the utility as required

4. Static switch: a semi-conductor based device which transfers the load from the inverter to the utility and back, without any interruption in the supply of power


UPS Operating in Passive Standby Mode

Operating Principle:

The inverter is connected in parallel with the AC input in a standby


Normal Mode Operation

In normal mode operation, the load is supplied by utility power via a filter which eliminates certain disturbances and provides some degree of voltage regulation. The inverter operates in passive standby mode.



Battery Backup Mode Operation

In battery backup mode operation, when the AC input voltage is outside specified tolerances for the UPS or the utility power fails, the inverter and the battery step in to ensure a continuous supply of power to the load following a very short less than 10 ms transfer time. The UPS continues to operate on battery power until the end of battery backup time or the utility power returns to normal, which causes transfer of the load back to the AC input (normal mode).

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