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Author Topic: Elementary My Dear Watson 3- phase alt and power  (Read 2016 times)
Lloyd
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« on: June 29, 2010, 07:35:39 PM »

http://www.radioelectronicschool.net/files/downloads/3phase.pdf

As the title says "Elementary My Dear Watson" some may find this boorish, it makes understanding 3-phase much easier...at least for me... I might not have had to harass Mobile_Bob as much if would have found this before I began my venture down "Custom Alternator Lane".

Can you answer without peeking?? Just for the record this is a test...I won't be grading. But if you need help with the answers, then this WP is worth the read.

Lloyd


Computing three-phase values using a wye-connected power source and a
delta-connected load

It is assumed the alternator has a line voltage of 240 V and
the load has an impedance of 12 Ω per phase. Find all missing values.
EP(A) _______ EP(L) _______
IP(A) _______ IP(L) _______
EL(A) 240 ___ EL(L) _______
IL(A) _______ IL(L)________
P _________ Z(PHASE) 12 Ω


Computing three-phase values using a delta-connected source and a wye connected
load

2. Assume the alternator has a line voltage of 4,160 V and the
load has an impedance of 60 Ω per phase. Find all missing values.
EP(A) _______ EP(L) _______
IP(A) _______ IP(L) _______
EL(A) 4160 V_ EL(L) _______
IL(A) _______ IL(L)________
P _________ Z(PHASE) 60 Ω


Computing three-phase values using a wye-connected source and two
three-phase loads

3. It is assumed that the alternator has a line voltage of 560
V. Load 1 has an impedance of 5 Ω per phase and load 2 has an
impedance of 8 Ω per phase. Find all missing values.
EP(A) _______ EP(L1) ______ EP(L2) ______
IP(A) _______ IP(L1) _______ IP(L2) _______
EL(A) 560 V__ EL(L1) ______ EL(L2) ______
IL(A) _______ IL(L1) _______ IL(L2) _______
P _________ Z(PHASE) 5 Ω Z(PHASE) 8 Ω
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JUST REMEMBER..it doesn't matter what came first, as long as you got chickens & eggs.
Semantics is for sitting around the fire drinking stumpblaster, as long as noone is belligerent.
The Devil is in the details, ignore the details, and you create the Devil's playground.
mike90045
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« Reply #1 on: August 09, 2017, 08:30:42 AM »

Question

Can a oversize (say 30Kva) 3 ph transformer be used to create 3 phase from a single 120V leg ? 
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mobile_bob
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« Reply #2 on: August 09, 2017, 09:48:06 AM »

"Can a oversize (say 30Kva) 3 ph transformer be used to create 3 phase from a single 120V leg ?  "

no!

bob g
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mike90045
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« Reply #3 on: August 09, 2017, 11:00:42 AM »

Can you expand on the NO ?   too much current needed on the 120v winding?
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Tom
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« Reply #4 on: August 09, 2017, 10:40:16 PM »

There is only 1 phase on one leg. You would need to rectify it to DC and run it through a 3 phase inverter, use a 120vac motor to turn a 3Ph generator, or easiest use a  3Ph variable frequency drive.
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Ashwamegh 6/1 - ST5 @ just over 1750 hrs

Tom
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« Reply #5 on: August 25, 2017, 04:23:49 PM »

"Can a oversize (say 30Kva) 3 ph transformer be used to create 3 phase from a single 120V leg ?  "

no!

bob g

  There is a contavaluted way with a T-Transformer and maybe a delta-wye page shift.....iirc.  Better to find a three phase VFD and supply it with single phase. 
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