The UPS Tests

It’s

that time of the year, when some of us at PCQ labs trip over UPSes and

undergo "shocking" experiences. Fortunately, we took care

of the first problem this time, but the second one is part of the deal. This

year, we subjected 26 UPSes to our battery of tests. We chose UPSes with a

minimum rating of 500 VA and a price not exceeding Rs 10,000. We also added

a new "surge" test this time to our existing test suite.

As always, we judged the

UPSes on performance, features, and price. The calculations were done using

a statistical model called the Brown-Gibson model. Here’s a brief

description of the tests.

Performance

"True"

VA rating

Here, we

tested whether each UPS lived up to its claimed rating. We subjected each

UPS to its rated load, and checked if it could sustain it for at least 30

seconds. If it failed to do so, we tested it on 80 percent load. If it still

failed, we tested it at 50 percent load. A power factor of 0.65 was used in

each case.

Voltage

tolerance: The

maximum and minimum line voltages at which a UPS can supply power to your PC

without switching to battery. A good UPS should not switch to battery even

when the line voltage varies by 20 percent of 220 V.

Output

stability: Too low an

output voltage can cause your PC to reboot while a high voltage could damage

it. Therefore, a UPS should be able to supply stable power to your PC. It

should be able to keep its output voltage within a range of 10 to 15 percent

above or below 220 V.

Switchover

characteristic:

This is the characteristic that a UPS displays

during the period when it switches from mains to battery or vice versa. We

measured this value for each UPS as described in the box.

Backup

time: Needless

to say, the higher backup time a UPS can give you, the better. We measured

the backup each UPS gave at 80 percent of its rated load. For those UPSes

that failed at 80 percent, we reduced it to 50 percent. Here we measured

whether a UPS was able to supply power above 220 V DC needed for a PC to

function. This is the rectified DC voltage across the SMPS capacitors of a

PC.

Cold

start: What

happens when there isn’t any power, and you need to do some urgent work on

your PC? Naturally, your UPS should be able to turn on your PC from its

battery. This is called cold start, and we checked whether each UPS was able

to lift 80 percent (or 50 percent if it failed there) of its rated load.

Float

voltage: UPSes have

SMF (Sealed Maintenance Free) batteries inside them. Each battery is made up

of six cells. When each cell is fully charged, it reaches a certain voltage

limit. Battery manufacturers specify this voltage range to be within

2.25-2.30 V DC. This is called the float voltage. If the float voltage is

above or below this range, the battery’s life gets affected.

Surge:

Voltage surges are sudden spikes in input voltage that can attain very high

values. If allowed to pass through, they can damage your PC. We added a new

test this time to check how a UPS reacts to surge voltage coming from the

mains. A good UPS should be able to suppress the surge in half a cycle of

output voltage, so that the surge reaches your PC for an extremely short

time duration. Anything longer than this could damage your PC. If a UPS

switches to battery the moment a surge comes in, your PC is still safe.

Pricing

We considered two aspects in

the pricing of a UPS–cost and warranty.

Cost:

Needless to say, the lower the

price of the UPS, the better it is, all other factors like performance and

features remaining the same. We awarded points to each UPS by comparing its

price to the lowest-priced UPS in our shootout.

Warranty:

The higher the warranty period

of the UPS, the more points it was awarded. We considered warranty including

batteries.

Features

We looked at

a wide range of features in each UPS–from documentation to how well

integrated it was in terms of design.

Indicators:

The bare minimum LED

indicators in each UPS should include indicators for mains power, when it’s

switching to battery, and when it’s being overloaded. If a UPS had

additional indicators–for example, for overload level or battery level–it

got additional points.

Documentation:

We looked at the comprehensiveness of the documentation that came with the

UPS. This should contain details on setting up the UPS, operational

descriptions, technical specifications of the UPS, as well as a

troubleshooting guide. A UPS with documentation that covered all these got

full marks.

Control

Software: Here, we

checked out whether the UPS had any control software, and if so, whether it

was included in the price of the UPS. A UPS with price inclusive of software

or with software that could be freely downloaded got full marks. Ones that

had software available but at charges over and above the price got less

marks, and one with no control software got no marks.

Compactness:

Our shootout included UPSes of

various sizes. We compared these on the basis of compactness in design,

depending on the number of batteries they used. For example, if a UPS with a

single battery was larger than one, which used two batteries, the latter

naturally got more marks than the former.

Other

features: Some

of the UPSes had features over and above the ones we’ve mentioned here.

These included a telephone port for surge protection over the

telephone/modem line, a surge protection port for printers (this gives surge

protection to the printer you connect to it, but doesn’t provide backup to

it), extended backup protection (you could connect more batteries to the UPS

for this), etc. Such additional features earned additional points for the

concerned UPS.