Message 21893 in TECH.WW
From: G8MNY
Date: Tue, 05 May 26 06:43:00 Z
Newsgroups: TECH.WW
Subject: AC 3 Phase Power
Message-ID: <58917_GB7CIP>
Path: N2MH4|GB7BED|GB7YEW|GB7CIP
R:260508/1449Z 30906@N2MH4.#SENC.NC.USA.NOAM LinBPQ6.0.24
R:260505/0651Z 10788@GB7BED.#21.GBR.EU LinBPQ6.0.25
R:260505/0651Z 17966@GB7YEW.#79.GBR.EURO LinBPQ6.0.24
R:260505/0643Z @:GB7CIP.#32.GBR.EURO #:58917 [Caterham Surrey GBR]
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 and distributed, it is more
efficient than other AC systems, except for DC that is the most efficient, but
that is difficult and costly to transform the voltage at high power.
The wire colour scheme may differ between countries & also the voltage!
up vectorialy, so at first sight 2x 230V does not make 415V between 2 lives.
Line
415V | | Brown o
415V | | | / \ Load Load
230V 230V 230V If loads balanced No Neutral
(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 and 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
(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
___________________
3 PHASE BRIDGE RECTIFIERS
Only 6 diodes produce a 3 phase bridge and that gives about 14% @ 300Hz (6x
________________
/_\ /_\ /_\ \|/
12 PHASE RECTIFIERS
With push pull or 3 phase bridge system, and using both star & delta windings
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.
________________________
Floating /_\ /_\ /_\ /_\ /_\ /_\ |
/_\ /_\ /_\ /_\ /_\ /_\ \|/
See my Tech bul "AC Theory".
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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