Subject: Re: VAX7000 3-phase
To: Gunther Schadow <firstname.lastname@example.org>
From: Chuck Dickman <email@example.com>
Date: 03/04/2002 19:25:23
Gunther Schadow wrote:
> One kW are 1.341 HP, so 1 kW at 110 V are 9.09 A.
> And then 1 HP at 110 V mounts to 6.72 W. There is
> something about the phase issue and how you calculate
> effective power (and there is where some conventions
> make a difference between VA and W even though they
> are the same physical unit.) But I forgot the detail.
> It's got something to do with P really not being
> U * I but there are integrals involved and capacitance
> and inductance turn the phase differences between
> U and I around, which makes for differences under
> idle vs. load conditions. This was all nice and clear
> to me when I did it in school but I forgot most of it
> since :-(
I think what you are thinking about is usually referred
to as "power factor". This is the shift in phase between
current and voltage that results from driving a reactive
load. It means a motor at "no load" can still draw 30%
full load current. It just doesn't "use" it.