Archived posting to the Leica Users Group, 1997/07/18
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>
> Well, actually, that only works in North America where we use 110 Volt
> electricity. The actual formula for this is P=I*E where P is the power in
> Watts, I is the inductance in Amps and E is the electromotive force in
> Volts. Given that, take the Watt rating of the device and divide it by the
> power source voltage and the result will be the load in Amps. This works
> for battery powered things as well.
>
A little bit of nitpicking. The formula P=I*E won't hold true for
stuff like fluorescent lights with ballasts or electric motors where
this is an appreciable power factor. These devices use up more
current because of their heavy iron cores which alternately and
absorb/regnerate power in their magnetic fields all without you seeing
any real "work" in terms of more useful light or heat.
The correct formula is P=I*E*(power factor). The power factor is a
number less than 1.0. So, for amperage, it is:
I = P/(E*(power factor))
which shows that your current draw is greater than a simplistic
formula would indicate.
- --
S. Khai Mong Imageware Inc, 323 N. First St, Ann Arbor, MI 48103
Email: khai@iware.com Voice: (313) 994-7301
WWW: http://www.iware.com/~khai Fax: (313) 994-0802