by January 5, 2000 0 comments
The
Weights
Switchover characteristic : 16
“True” VA rating 15
Maximum output  14
Minimum output  14
Surge test  15
Maximum switchover voltage 8
Minimum switchover voltage  8
Backup time  5
Cold start  3
Float Voltage  :   2
100
Features
Documentation  33
Indicators  27
Control software  20
Compactness  13
Others  7

100
Pricing:
Cost  70
Battery warranty : 30
100

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.

Load sustained  Points awarded
100 percent 2
80
percent 
1
50 percent 0

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.

Stay
on main even when mains 
voltage varies by 
 Points awarded
>20
percent (best)
2
10-20
percent (good) 
1
10 percent
of 220V (average)
0

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.

Output
voltagevariation
 Points awarded
Less than
10 percent
2
10-15
percent (average) 
1
Over 15
percent (poor)
0

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.

Droop
Voltage
 Points awarded
Above 220 2
80
percent 
1
50 percent 0

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.

Surge
correction
 Points awarded
One
half-cycle
2
Switched to
battery 
1
More than
one half-cycle
0

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.

The tests and test benches
were designed by Dr Arun K Agarwala, IDDC Labs, IIT
Delhi. Tests were done under his supervision at PCQ Labs, by Anil
Chopra, Ashish Sharma,
and Lalit Juneja. The final reviews
and opinions are those of PCQ Labs and PC Quest, and not of IIT Delhi

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.

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