UPS Faqs

What is an Uninterrupted power supply and its functions?

An Uninterrupted power supply (UPS) is a system intended to solve the mains disturbances and mains failure. The batteries attached to the UPS enables the user to work during mains failure. This is done by putting the UPS between the mains and your computer.

What is the difference between the UPS catagories: Off line, Line interactive and Online ups?

Offline UPS

The Offline UPS supplies (or routes) the incoming mains supply directly through to the output usually through a relay contact. Some high frequency noise filtering and surge suppression may be included in this path.The UPS swiches on its inverter as soon as mains supply failure is detected or below the normal load and simultaneously switches the output relay to the inverter side to supply battery sourced power to the load. This transition involves a delay on account of the time to reliably detect mains failure and switch over a relay, and the output is broken for this period (usually for 2 to 12msec).

Offline UPS are usually the least exensive as compared to the other two.

The Block diagram of inverter section of Online ups is shown:

Line interactive UPS

The true Lineinteractive ups regulate the input power and provide the output between an specifice output voltage range, means in this system the inverter plays a dual role of charging the battery when mains supply is present as well as regulating the output voltage and working as a normal inverter in absence of mains supply. Lineinteractive UPS offers enhanced power protection over the basic Offline designs by providing additional line conditioning. But these ups has the change over time between 4ms to 6ms.

Online UPS

An Online ups is the one in which the inverter (and electronic section called inverter) always supplies power to the protected load and hence the same quality of power is ensured all the time.

Working: When mains supply is present, the inverter derives its power from thee mians supplied rectifier and the backup batteries are also kept in charged state. When the mains fail, the source of DC power for the inverter section shifts to the battery without any break (zero changeover time) whatsoever in the output to the Inverter. It also bears all the vagaries and noise borne out of the mains supply and insulates the secure bus supply from it.

An Online ups is especially usefulll for sensitive and critical equipments/devices. It comes from single phase application to 3phase application. Custom made output can easily achieve in Online ups system design.

Is UPS system really necessary for my computer?

As an experienced & conscientious computer user, you have faith in the dictum GIGO and you take precautions to see that ‘garbage’ doesn’t enter your system through software. But there is one more source of garbage, of a more serious nature, which is not normally taken care of. That is in the form of garbage power input to the computer. It is more serious because besides malfunctioning and operation problems it can also cause permanent damage to your computer.

What exactly is meant by ‘garbage’ power?

It is common knowledge that there are fluctuations in utility supply .For example, some times the utility voltage is as low as 170 to 160 volts and high as 280 to 300 volts. Besides this, there are many more hidden culprits associated with utility lines like sags and surges, oscillatory transients, EMI and RFI, brown outs, or total loss of power.

How does all this apply to my computer?

The equipment to which you are feeding this power is extremely sensitive to the quality of power and is termed as critical equipment. Imagine a sudden failure of computers during busy hours when a critical operation is in progress. All this can occur due to garbage power fed to such equipments. The loss is invaluable and you just cannot take any chances.

The above problem is of malfunctioning or operational nature. These can be extremely frustrating, time consuming and expensive. Besides, like all electronic circuits ,the computer circuits can also undergo irreparable damage due to high voltage surges and spikes, which can reach several kilovolts.

How does an UPS eliminate these aberrations and give clean power?

The important blocks in a UPS and their functions are listed below: These shall be helpful in explaining the functioning of the UPS.

Line filter: Eliminates line born noise and spikes.

Inverter: The smooth DC is inverted by two transistors connected in push-pull configuration. The switching device (Transistor OR IGBT or MOSFETS) is used and controlled by a sophisticated control circuit.

A closed loop voltage feedback control is used to keep the output voltage constant even under widely varying DC voltage conditions. A proportional increase in the widths of the pulses causes an increase in voltage and a proportional reduction in width decreases the voltage. This means that the voltage control action is a great advantage for taking care of dynamic loading conditions in a computer like switching on and off of disk and tape drives as well as movement of the accessing head. A current feedback protects the inverter even from short circuit by turning off the control pulses going to the transistor / IGBT/ MOSFET base.

3) Output Filter: The output filter converts the inverter output to a smooth AC with very low distortion. The nature of the filter is such that it can deliver inrush and surge currents demanded during switching on of computer loads.

Is computers type of load some special category of load?

Most certainly. A number of devices in various computer installations are studied, information is collected from device manufacturers and after taking all this into account the system is designed. JET-Electro has been doing this work in close co-operation with experienced people from computer application and computer maintenance fields. Therefore JET-Electro is in a position to offer its users a unique advantage over others.

How do I size my requirement ?

You can ask to your supplier or call out technical team for this details.

How does one select the battery?

Battery selection depends upon the back up time required which in turn depends upon the frequency of power failure, average programme length and the presence of other back up source like a diesel generator set. One thing to remember is that the ampere hour ratings quoted by battery manufacturers are on a ten hour discharge basis and normally the back up time required will be much shorter; sufficient either to finish an almost complete job or to take a systematic shut down or to start the generator set. However, when the battery is discharged in a shorter time a derating factor has to be used which incidentally does not vary below 20 to 30 minutes. So approx half an one hour is a sensible back up time to select.

How long batteries last in a UPS?

Battery life depends upon number of factors , viz.

– Temperature

– Number of discharges experienced

– Number of deep discharges experienced

– Specification of the batteries

Battery life is halved for every 10 degrees Centigrade temperature increase above it’s specified operating temperature (usually 25 degree Centigrade).

UPS batteries are designed for maximum life in ‘typical’ use i.e. long periods of continous low charge and occasional minor discharges.

At installation time, the battery is at 100 percent of rated capacity. Each discharge and subsequent recharge reduces the relative capacity of the battery by a small percentage.The length of the discharge cycle will determine the reduction in battery capacity.

So-called deep discharges on a repeated basis will reduce the life of the battery.

The loaf of “bread” analogy is most often used to illustrate the relationship between cycling and battery life. A loaf of bread can either be cut into many thin slices or a few thicker slices. Similarly, a UPS battery can provide power over a large number of short cycles, or fewer cycles of long duration.

The IEEE defines “end of useful life” for a UPS battery as being the point when it can no longer supply 80 percent of its rated capacity in ampere-hours. The realationship between amp-hours and load protection time is not linear, a 20% reduction in capacity results in a much greater reduction in protection time. For example, a UPS battery that supports a full load for 15 minutes when new, will support the same load for only about 8 minutes when it reaches its defined “end of life”.

When your battery reaches 80% of its rated capacity, the aging process accelarates and this is the time when the battery should be replaced.

No UPS battery will last forever – even one that experiences minimal use.This is because UPS batteries are electro-chemical devices whose ability to store and deliver power slowly decreases over time.So, even if you follow all the guidelines for proper storage temperature and maintenance, you still must replace them after a certain period of time.

One of the batteries has failed in the UPS battery bank, is it alright to replace just one battery?

If the batteries are less than twelve months old then the failure could be due to a manufacturing or material fault. In this instance the failed battery can be replaced after confirmation by testing the whole battery bank.

In general once the batteries are over twelve months old, the failure is more likely to be due to age, environment or usage and the whole bank should be replaced. Failure to replace the whole bank could result in the new battery not being charged properly and your load being at risk if any or all of the older batteries fail.

How do I maintain and service the batteries and the UPS?

Gradual decrease in battery life can be periodically monitored and evaluated by :

– Voltage checks

– Load testing

– Checking for proper battery connections.

– Checking for battery water (in case of Automative batteries)in Online UPS batteries connection in ser

CAUTION: Do not touch the batteries terminals without any technical knowledge, always call to the related service person.

How long can I leave the UPS switched off without damaging the batteries ?

As long as the batteries are fully charged when the unit is switched off they will not require charging for three months.

Cold start feature of Power Pack Line Interactive UPS isolates the batteries from the UPS circuit and thus the UPS can be switched off for longer period (six months approx.) without damaging the batteries.

How do I know what to buy ?

Following parameters should be considered before buying

– Company reliability, experience, stability, customer service.

– Technology and features.

– Price and performance. ( An Indian company Like JET Electro is providing you the product of international quality in very reasonable prices, you can trust the products for more than 15 years of life. (regular maintenance is necessary).

Does JET-Electro form its own specifications?

No! The specifications are formulated based on International market requirement. (Custom made ups is also available)

How cost effective is the investment in an UPS system?

It is really quite simple. If you consider the average time lost & multiply it by the cost of computer time which you already know you will arrive at the direct loss. This, however, does not take into account indirect losses like job scheduling, trouble shooting, as well as corruption of files and damage to electronic circuits. If you take all these into account , definitely a JET-Electro system will pay for itself in less than one year.

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