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G8MNY > TECH 24.05.20 09:22l 142 Lines 6515 Bytes #999 (0) @ WW
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Subj: AC 3 Phase Power
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Sent: 200524/0821Z @:GB7CIP.#32.GBR.EURO #:57322 [Caterham Surrey GBR]
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From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Aug 08)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
3 PHASE POWER
This is how AC power is normally generated & distributed, it is more efficient
than other AC systems, except for DC that is the most efficient, but that is
difficult & costly to transform the voltage at high power.
The wire colour scheme may differ between countries & also the voltage!
The phase angle between phases is 120ø, because of this the voltages are added
up vectorialy, so at first sight 2x 230V does not make 415V between 2 lives.
You divide by û3 (1.732) to get the line to neutral voltage.
Line
BROWN ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ STAR LOADS DELTA LOADS
(red) /³\ /³\ /³\ o Brown
415V | | Brown o
\³/ 415V | Load / \
BLACK ÄÄÄÄÄÄÄÄÄÄÄÄÄ | ³ / 60ø \
(yellow) /³\ | /³\ | 120ø o 120ø 414V 415V
415V | | | / \ Load Load
\³/ \³/ | | Grey 120ø Black / 60ø 60ø \
GREY ÄÄÄÄÄÄÄÄÄ | | Load Load o______ 415V ______o
(blue) /³\ | | o o Grey Load Black
230V 230V 230V If loads balanced No Neutral
\³/ \³/ \³/ centre = neutral &
BLUE ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ loads all get 230V
(black) (neutral)
The 3 line currents are normaly loaded up to be as equal as possable to reduce
the current in the neutral cable normal the same gauge. But Philip M1EUR
reports that Neutal cable may need to be 2x the gauge (CSA) if electronic loads
with very high harmonic current are used!
NEW COLOUR HAZARDS !
New EU colours are Brown Black Grey for Lives & Blue Neutral
replacing Red Yellow Blue for Lives & Black Neutral. Green/Yel earth.
N.B. the lethal change for both BLACK & BLUE colours!
Also note the colour layout of new 3 phase 4 core cable means, that a joint can
not be straight to an old cable & bigger joints casings will be needed to allow
for at least 2 cores to be bridged!
Single phase will change from Red live, Black Neutral to Brown & Blue
respectifully. But highly confusing in a 3 phase board with both old black
wire loads for Neutrals & Black Bus feed for live! Brown & Blue sleeves are to
be used over Red & Black wires!
3 PHASE TRANSFORMERS
Like any transformer the voltage can be changed, or isolated etc. The
difference being that 3 legs of the transformer carry the windings rather than
just the middle. ÚÄÄÄÄÄÄÄÄÄÄÄ¿ The winding connections can be either STAR or
³ ÚÄÄ¿ ÚÄÄ¿ ³ DELTA or combinations of both.
ÚÁÄÁ¿ÚÁÄÁ¿ÚÁÄÁ¿ When cross connected star-delta a rotation of
Windings->³ 1 ³³ 2 ³³ 3 ³ 90ø in phase occurs. (30ø to other phases)
ÀÂÄÂÙÀÂÄÂÙÀÂÄÂÙ .
Laminated ³ ÀÄÄÙ ÀÄÄÙ ³ | or / \ becomes _ / or /'³
Core ->ÀÄÄÄÄÄÄÄÄÄÄÄÙ / \ '---' \ '\,³
(due to magneto striction of the core, audio hum given off from the steel is @
300Hz on 50Hz system)
3 PHASE RECTIFICATION
With rectification 3 diodes gives about 30% ripple at 150Hz (3x supply) the
ripple is not much as singe phase, as some of the 120ø voltages overlap.
___________________
_³_ _³_ _³_ /|\
/_\ /_\ /_\ | 100% ´ _.-._ _.-._ _.-._ Â Ripple
Br ÄÄÄÙ ³ ³ Raw 70%_³ / \ / \ / ³
³ ³ DC ³ ³ ³ ³ ~
Bk ÄÄÄÄÄÄÄÄÄÙ ³ | ³ ³ ³ ³ ³ ³
³ | ³³ ³ ³ ³ ³
GyÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ | ÅÄÄÄÄÄÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄ Phase Angle
\|/ 0ø 120 180 240 310 360ø
BlÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
3 PHASE BRIDGE RECTIFIERS
Only 6 diodes produce a 3 phase bridge & that gives about 14% @ 300Hz (6x
supply) ripple peak to peak, as more of the 60ø voltages overlap.
________________
_³_ _³_ _³_ /|\
/_\ /_\ /_\ | 100% ´ _.-._.-._.-._.-._.-._ Â Ripple
Br ÄÄÄ´ ³ ³ | 86% /³ / / \ / \ / \ / \ / ~
³ ³ ³ | ³ ³ ³ ³ ³ ³ ³
Bk ÄÄÄ)ÄÄÄÄÄ´ ³ Raw ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³
³ ³ ³ DC ³³ ³ ³ ³ ³ ³ ³
Gr ÄÄÄ)ÄÄÄÄÄ)ÄÄÄÄÄ´ | ÅÄÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄ Phase Angle
_³_ _³_ _³_ | 0ø 60 120 180 240 310 360ø
/_\ /_\ /_\ \|/
ÀÄÄÄÄÄÁÄÄÄÄÄÁÄÄÄÄ
12 PHASE RECTIFIERS
With push pull or 3 phase bridge system, & using both star & delta windings
there can effectively be 12 lives that are only 30ø apart. This can also be
achieved with push pull phase on each leg of the transforner.
| \ / \ | /
* + * = *
/ \ | / | \
Using 2x 3 phase bridges or 12 winding & diodes the resultant ripple is only
about 3.6% @ 600Hz, assuming all the voltages are equal! Very little filtering
is then needed for say a 100kW Tx HT supply.
________________________
_³_ _³_ _³_ _³_ _³_ _³_ /|\
Floating /_\ /_\ /_\ /_\ /_\ /_\ |
. BrDÄÄ´ ³ ³ ³ ³ ³ | 100% ´ _.-.-.-.-.-.-.-.-. = Ripple
/ \ BkDÄÄ)ÄÄÄ´ ³ ³ ³ ³ | 96% /³ / / /\/\/\/\/\/\/\
'---' GyDÄÄ)ÄÄÄ)ÄÄÄ´ ³ ³ ³ | ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³
Windings ³ ³ ³ ³ ³ ³ Raw ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³
BrSÄÄ)ÄÄÄ)ÄÄÄ)ÄÄÄ´ ³ ³ DC ³³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³
| BkSÄÄ)ÄÄÄ)ÄÄÄ)ÄÄÄ)ÄÄÄ´ ³ | ÃÄÄÂÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄ Phase Angle
/ \ GySÄÄ)ÄÄÄ)ÄÄÄ)ÄÄÄ)ÄÄÄ)ÄÄÄ´ | 0ø 30 60 120 180 240 310ø
_³_ _³_ _³_ _³_ _³_ _³_ |
/_\ /_\ /_\ /_\ /_\ /_\ \|/
ÀÄÄÄÁÄÄÄÁÄÄÄÁÄÄÄÁÄÄÄÁÄÄÄÄ
See my Tech bul "AC Theory".
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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