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G8MNY > TECH 23.04.24 15:31l 56 Lines 2656 Bytes #4 (0) @ WW
BID : 6064_GB7CIP
Read: GUEST
Subj: Variacs
Path: JH4XSY<N3HYM<W0ARP<LU9DCE<EA2RCF<I0OJJ<GB7CIP
Sent: 240423/0624Z @:GB7CIP.#32.GBR.EURO #:6064 [Caterham Surrey GBR] $:6064_GB
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (New Dec 07)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
Varaic is a traded name of The General Radio Co. for a variable tapped toroid
mains auto transformer (non isolating) usually with up to 17% overvoltage.
260o__ Ratings are normally in amps. But this can be
240o__||) fuse confusing as the laminate core will have a power
LÄo-oÄÄÄÄo__||)<ÄoÄoÄL rating as a 50% step down auto transformer which is
fuse 220 ||) when the core has the maximum work to do of half the
||) output rating, as half the output current flows
INPUT ||) OUTPUT through the top section & half comes up from the
-10o__||) lower. However using a few % from the top or bottom
NÄÄÄÄÄÄÄÄo__||)______N you can easily cook the winding as the core can put
0 ³ out huge currents. So an input & output fuse is needed
EÄÄÄÄÄÄÄÄoÄÄÄĮÄÄÄÄÄÄÄE to protect it! e.g. 250VA one needs a 1.5A slow blow
mains fuse & a 3A fast blow on the output should do.
Wiper _ Turns
ÜÜÜ======³ ³ Bared _.śĀĀĀś._
Ś---------------------æ .ś~ /~\ ~ś.
³²²²²²²²²²²²²²²²²²²²²²³ .' \ ³ Ū ³ / '.
³²²²²²²²²²²²²²²²²²²²²²³ / .ś' ³ ³ 'ś. \
³²²²²²²²²²²²²²²²²²²²²²³One layer Ž . ³ ³ . Ż
³²²²²²²²²²²²²²²²²²²²²²³of winding Ż___ / \ ___Ž
³²²²²²²²²²²²²²²²²²²²²²³ ŽÄÄÄ: ³ 0 ³ :ÄÄÄŻ
³²²²²²²²²²²²²²²²²²²²²²³ Ż~~~ \ / ~~~Ž
³²²²²²²²²²²²²²²²²²²²²²³ Ž ' ~---~ ' Ż
³²²²²²²²²²²²²²²²²²²²²²³ \ 'ś. .ś' /
³²²²²²²²²²²²²²²²²²²²²²³ '. / ' śśś ' \ .'
~~~~~~~~~³ ³~~~~~~~~~ 'ś._ ³³³ _.ś'
³ ³Shaft ~~ĮĮĮ~~
ĄÄŁfor
knob
Bad arcing can damage the brush & windings. Do check the brush & spring out if
you have arcing. Insulation damage can cause fires as a shorted turn has almost
infinite current available.
With toroidals the winding are exposed on the outside & variacs even more so if
the bare windings are not fully encased,
See my buls "70-260V Mains Auto Transformer", "Constant Voltage Transformers",
"Maplin Mains Meter 2000MU-UK", "Portable Appliance Testing" & also "Mains
Power Protection".
Why Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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