Phase Power & Fuses

• To: tesla-at-pupman-dot-com
• Subject: Phase Power & Fuses
• From: RWB355-at-aol-dot-com (by way of Terry Fritz <terryf-at-verinet-dot-com>)
• Date: Wed, 07 Oct 1998 02:52:11 -0600
• Approved: terryf-at-verinet-dot-com

Mail was: Power Applied?, and further wiring tricks..
 
 Original Poster: "Mike Magnus" <mike-at-gmx-dot-com> 
 
 In the US anyway, the most common household service is 120/240V single
 phase and the line terminals are 180 deg. out of phase with each other. If
 you're dealing with a 3 phase star or Y service (common here in small
 businesses) you get 120 line to neutral, but only 208V line to line because
 the line terminals are 120 deg out of phase.
 
Hi Mike,
Sorry, that was my mistake in assume the 240 volts came from a 3 phase setup
(line to line).

Now Assuming:
3 phase supply
220 V from phase to N (3x)
380V from phase to phase
Each phase is 120° out of phase to the next phase.
Assuming 3 fuses with 20A

We agree on:
You can draw 3 x 20 A from the mains (L1, L2,L3 to N) or in a 3 phase star (Y)
connection for a total of 60 amps or a total of (3 x 4.4 kVA) 13.2kVA at 220
V.

Now comes my question:
How about the delta connection? Would this mean you could only draw 20A?. 
Or how about (being the same question, really) from phase to phase (i.e
380V).This would mean less output on a delta connection.
I always figured you have to take the phase difference into account. I never
could figure this out in a satisfing way.


hope you can help,
Coiler greets from Germany,
Reinhard

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