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# Dual Athlon MP 1U units

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Robert G. Brown rgb at phy.duke.edu
Sun Jan 27 10:39:39 PST 2002

On Sat, 26 Jan 2002, Bari Ari wrote:

> Bari Ari wrote:
>
>
> > A power factor corrected power supply will match the capacitive loads of
> > the semiconductors on the motherboard to raise the power factor closer
> > to 1. Resistive loads account for very little on a well designed
> > motherboard.
>
>
> Just to clarify -- Resistive loads other than the semiconductors.
>
> Bari

Dear Bari,

You mean resistive loads other than the ones with resistance that
actually produce the heat we're talking abotu?

;-)

Just kidding.  In the spirit of correcting our goofball errors, my own
algebra was off by 1/sqrt 2.  Let's try:

P_av = 1/2 V_max I_max \cos{\delta} = V_rms I_rms \cos{\delta|

so that V_rms = 1/sqrt{2} V_max and I_rms = 1/sqrt{2} I_max.  So if peak
voltage is 120V and peak current is 1.7A and \delta = 0 (power factor
unity), peak power is 204 W and average power is 102 W.

My error is worse than your error.  I actually teach this stuff -- you'd
think I could get it right... :-o>-  (<- "Oh, my!" smiley.)

rgb

--
Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu