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G8MNY  > TECH     11.06.12 04:33l 64 Lines 2353 Bytes #999 (0) @ WW
BID : 45747_GB7CIP
Read: DK3UZ GUEST OE7FMI
Subj: 70-260V Mains Auto Transformer
Path: DB0FHN<DB0MRW<DB0ERF<IZ3LSV<IK2XDE<DB0RES<ON0AR<GB7CIP
Sent: 120610/2203Z @:GB7CIP.#32.GBR.EU #:45747 [Caterham Surrey GBR] $:45747_GB
From: G8MNY@GB7CIP.#32.GBR.EU
To  : TECH@WW

By G8MNY                                (New Jul 11)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
This is a poor variac substitute, but made with a suitable transformer & large
wafer switch, it can provide useful mains test voltages.

Voltages shown are for simplicity of calculation only!

CIRCUIT
                  旼컴컴컴컴컴컴컴컫컴컴훟 260V
 Fuse 1  On       �     旼컴컴컴컴�)컫컴훟 240V
L 훟-o컴훟\o컫컴컴)컴컴�)컴컴컴컫컴)�)컴훟 220V <컴컴 L
(220V)       �.   �     �   -   �  � 쳐컴o 200V
              )||.쳐컴컴)컴훟 <켸  � � 旼o 180V
         110V )||( 40V  �      220 읕)�)훟 150V
        ______)||(______�      110   쳐)훟 120V
       �______.||( 20V  �   + <컫컴컴)�)훟 110V
       �      )||( 0V  LAMP o   �    읕)훟  90V
       � 110V )|| 읕컴컴좔컴좔컴)컴컴컴좔o  70V
       �   ___)||               �
       읕�(컴컴컴컴컴컴o-o컴컴컴�
          �           Fuse 2
N 컴컴컴컴좔컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� N

E 컴쩡컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� E
   _�_
     
Here the 110/220V switching & phase reverse switching (+ or -) of the 40V
secondary is not shown. If a good multi wafer switch is not available, then a
plug board may be more suitable.

SAFETY
To stop switch arcing or shocks on a plug board, only change voltage with the
mains OFF! The inclusion of a 20V lamp (not accessible!) is useful to remind
you!

All housing & wiring etc. should be up to mains standards & also let heat out.

The power rating of the transformer will set the max current at a voltage...

 VOLTS     MAX LOAD CURRENT       e.g. 80W Transformer
  260     Full Secondary                  2A
  240     1.5 x Secondary                 3A
  220       Infinite                    Fuse Limit
  200     1.5 x Secondary                 3A
  180     Full Secondary                  2A
  150     2x Transformer rating         0.6A (220/80 x2)
  130     2x Transformer rating         0.6A
  110     2x Transformer rating         0.6A
   90     2x Transformer rating         0.6A
   70     2x Transformer rating         0.6A

So for an 80W transformer Fuse 1 can be 2 or 3A, & Fuse 2 a 1A.

See also my tech bul on "Maplin Mains Meter 2000MU-UK","Mains Power Protection"
& "Saveplug Motor Economiser".


Why don't U send an interesting bul?

73 De John, G8MNY @ GB7CIP


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