UPS Information

Uninterruptable Power Supply (UPS)

Due to power outages, the first UPS was built in the 1960's to protect sensitive equipment. This first unit had 4 important components. A Battery, Inverter, Charger and a Transfer switch. Today these 4 components are still the main building blocks of any UPS.

The boost in the computer industry enhanced sales of UPS's. This led to the development of highly complex systems which enhances the protection, supervisory circuits, self-checking and communication functions.
UPS stands for Uninterruptible Power Supply. It is an instrument connected between the electric grid (ESCOM) and the consumer (computer). It comprises of electric hardware and rechargeable batteries.

The aim of the instrument is to supply continuous undisturbed and conditioned power to the critical load. The energy for powering the load comes from the utility, or from the battery upon mains outage.

A UPS does three things for you.
First, it filters the power your machine sees, smoothing out spikes and voltage fluctuations that can stress or even damage your electronics. Secondly, it provides a certain amount of dwell time in the event your power goes out entirely — this can often get you through brownouts and short blackouts. Thirdly when the UPS is about to run out of power it can arrange a graceful shutdown of your computer so that no unpleasant things happen to your disk.

Information needed to size UPS

The run-time for a UPS depends on the type and size of batteries and rate of discharge, and the efficiency of the inverter. The total capacity of a lead-acid battery is a function of the rate at which it is discharged.

Manufacturers supply run-time rating in minutes for packaged UPS systems. Larger systems (such as for data centers) require detailed calculation of the load, inverter efficiency, and battery characteristics to ensure the required endurance is attained.

There are 3 types of UPS's.

Backup UPS
Also called a off-line, or stand-by UPSUpon mains power outage, the UPS enters a Backup mode. The Transfer Switch connects the load to the output of the inverter. The inverter now feeds the load from the battery and will continue to do so until utility power is restored.Backup systems are generally used for low power installations, small offices, personal home computers and other less critical application, where eliminating 85% to 90% of computer malfunctions caused by power failures, is satisfactory.

Line Interactive UPS


Line Interactive UPS, is also called a Smart UPS, These systems are also based on stand-by principle, working normally directly from mains, switching to battery

(via the inverter) upon mains outage.

The line Interactive UPS is equipped with additional transformer type Automatic Voltage Regulator ( AVR) on the Bypass line (between Mains input and the Transfer switch) If power outage is prolonged, the UPS before turning off, will warn the user by means of an audible beep signal, to enable manual shut down of user's critical loads.

The Line Interactive UPS is a professional solution for business application where the main concern is to provide protection from most utility grid disturbances

On-Line UPS

Also called Double Conversion UPS, or True On-Line UPS. This is the ultimate solution for all applications from one or two kilowatts up to Megawatt sized consumers.

Here, the load is constantly fed from the Inverter, providing conditioned, stabilized sinusoidal voltage. The utility line in these systems backs up the UPS in case of UPS malfunction. The Transfer switch will automatically transfer the load to mains in case of overload or UPS failure.

The On-Line unit comprises two converting stages.

The first stage converts the incoming AC power to DC, thus creating a dc-buss, which is fed either from mains or from storage battery.

The second stage converts the DC power back to conditioned AC in order to feed the critical load.

Filters on the DC buss and fast regulating circuits in the converters practically isolate the load from any abnormal utility behavior.

In normal operation, load energy comes from mains, via the Rectifier and the Inverter.

Upon mains outage the battery supplies the energy, which the load requires (by the dc/ac Inverter).

Should the mains voltage return before the battery was fully discharged, the Rectifier will feed the load through the Inverter and start a battery recharge regime to compensate for the lost charge.

Otherwise, the UPS will turn off when battery becomes fully discharged. The UPS will resume automatically normal operation upon mains restoration. Also here, the Rectifier will feed the load via the Inverter, recharging the battery.

The Output voltage of an On-Line UPS is generally stabilized within one percent tolerance. Output frequency is locked to input if it is within preset tolerance band, otherwise a free running crystal controlled clock will dictate the output.

The merits of Double Conversion ON -Line system make it the preferred choice for business and industrial applications. It is the best solution in spite of the added system and electricity costs.


Features and benefits of the Power Shield range which are manufactured in Australia.

  • It offers the best power protection, covering any and all types of mains disturbances.
  • There is no size limit. Standard ON-Line UPS's are available to backup any installation.
  • With the right system, no practical limit exists on the available back-up time. Batteries may be added to increase backup time.
  • Many systems allow power extension to satisfy the needs of a growing enterprise
  • Units can be connected in parallel redundant configuration, for increasing reliability.
  • In addition, this is the best choice, considering such issues as modularity, ability to work from generator, power factor correction, maintenance, hot swapping, fault clearing, supervising, and communicating.

Target market

Information technology networks

These facilities, buildings, operations, companies and many other applications need the assurance of power backups in the case of interruptions due to power failures, surges and lightning strikes.

Troubleshooting and common problems

  1. NO LOAD SHUT DOWN -- This is the most common problem faced with these types of UPS. These UPS switch off when there is no load connected to it. So we must ensure that any device connected to it always powered on so that UPS can give the output.
  2. USAGE OF COLD START -- if the UPS is not getting on early in the morning though it was working last evening, we must try to manually switch it on by pressing the “COLD START” red switch besides MAINS on switch. We need to keep this COLD START Switch pressed for few seconds so that it gives the output and also ensure the connected devices are powered on.
  3. CHARGING – If the UPS is switched off in the evening then it will require at least 6-8 hrs for complete charging so as to give a backup of 30 min otherwise it may give less back up. So we must ensure that we keep MAINS always ON.

Maintenance schedule

Regularly perform a mains failure / battery discharge test.

Refer all services and repair work to a professional service provider as dangerous voltages exist within the system even when switched off.