[clug-talk] Slightly OT Power usage

Niels Voll nvoll at voho.com
Fri Nov 19 22:09:40 PST 2004

moderate +1, informative   :)

thanks Dave, that was excellent info for us non electrical engineers :)

In your experience, do you have the sense, that the quality of city 
power varies quite a bit between various areas in the city? I've 
sometimes wondered about that.


Dave Watkins wrote:

>Hi All,
>Concerning UPS's and surge protectors.......
>I will only use line interactive UPS's in my shop or with my clients. The
>protection offered by this type of UPS is far superior to the standard
>battery backup. I've included a link to APC's white paper detailing the
>different types of UPS's available. Basically they provide filtered,
>conditioned and regulated power via the battery and avoid a direct
>connection to the city grid choosing to run things through the battery
>instead. Battery life is shortened slightly but that is a small price IMHO.
>Concerning the use of surge protectors in most cases you get what you pay
>for. It's as simple as that. Just for fun one day I hooked a battery charger
>to a surge protector and placed a rheostat in line between the surge
>protector and a 220 V power supply. I was surprised to see the range that
>they would accept without tripping. That increase or decrease in voltage,
>known as sags or surges, can cause as much damage to today's modern systems
>and the data on them. Today's systems are more delicate due to the smaller
>voltages required to operate. During a discussion with the City of Calgary's
>Electrical Dept I was told that the voltage provided by the City can vary by
>as much as 15% from 110V. I was also surprised to find out that this
>variance is "normal" according to the City and within the contract we all
>have accepted by using their power. Most surge protectors do not have the
>circuitry within to react fast enough to these surges or sags. Another
>consideration is the speed which a surge protector will kick in, sometimes
>called the clamping voltage. With many of the cheaper units the damage has
>been done before the protector realizes there has been a spike.
>Sag   - slow decrease in supplied voltage
>Surge - slow increase in supplied voltage
>Spike - rapid increase in supplied voltage
>Drop  - sudden loss of supply voltage
>For what it's worth, I've used plenty of APC's products in the past and they
>seem to work well. I have had to replace a few units under warranty that
>failed AFTER they were hit with a spike in all but one case there was no
>damage to the attached equipment and in the one case where a motherboard was
>fried APC paid for a replacement board without any hassles. They were quite
>happy to ask a few questions and cut a cheque for the new board while at the
>same time sending out the replacement UPS.
>Rider computers on 32nd Ave NE frequently have used UPS's and most have good
>batteries in them. They will usually test them and mark the usage in
>minutes. Replacement batteries can be purchased from Battery World if
>Hope this helps someone......
>Dave Watkins
>Abacus Technologies
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