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G8MNY  > TECH     02.12.18 10:30l 69 Lines 2690 Bytes #3 (0) @ WW
BID : 47540_GB7CIP
Read: GUEST
Subj: 70-260V Mains Auto Transformer
Path: ED1ZAC<ED1ZAC<GB7CIP
Sent: 181202/0914Z @:GB7CIP.#32.GBR.EURO #:47540 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To  : TECH@WW

By G8MNY                                (Updated Dec 12)
(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컴컴컴컴컴컴컴컴컴컴컴쩡컴o 260V
 Fuse 1  On            旼컴컴컴컴컴컴컴쩡)컴훟 240V
L 훟-o컴훟\o컫컴컴)컴컴)컴컴컴컴컫컴컴))컴훟 220V <컴 L
(220V)       .           -           쳐컴o 200V
              )||.쳐컴컴)컴훟 <컴켸       旼o 180V
         110V )||( 40V        220       쳐)훟 150V
        ______)||(______      110/20   쳐))훟 130V
       ______.||( 20V     + <컴컴컴컫)))훟 110V
             )||( 0V  LAMP o          쳐))훟  90V
        110V )|| 읕컴컴좔컴좔컴컴컴컴)))컨훟  70V
          ___)||                       읕컴o  40V
                       110           읕컴컴o  20V
       읕(컴컴컴컴컴컴컴컴훟 <컴훟-o켸
                      20/40o    Fuse 2
N 컴컴컴컴좔컴컴컴컴컴컴컴컴좔컴컴컴컴컴컴컴컴컴컴컴컴컴 N

E 컴쩡컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴 E
   __

Here the 110/220V switching & phase reverse switching (+ or -) of the 40V
secondary is not shown. The two lower secondary voltages of 20 & 40V are
available with this complex switching.
If a good 12 position 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
   40     Full Secondary                  2A
   20     Full Secondary                  3A

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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