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I bought this transformer As I need to convert 230vac to 18vac

enter image description here

As can be seen in the image it has 2x 115V terminals and 2x 9v terminals so I assumed it would be centre tapped but this does not seem to be the case.

There is no continuity between the top left terminals and top right, the setup is the same for the lower 9v terminals.

My question is, can I safely bridge the 2 middle top terminals and 2 middle lower terminals to form a 230v winding and 18v winding respectively?

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    \$\begingroup\$ Datasheet says? \$\endgroup\$
    – Tyler
    Sep 26, 2016 at 15:07
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    \$\begingroup\$ Try page 5 of the datasheet. \$\endgroup\$
    – Tyler
    Sep 26, 2016 at 15:09
  • \$\begingroup\$ Here it is. \$\endgroup\$
    – Eugene Sh.
    Sep 26, 2016 at 15:10
  • \$\begingroup\$ Thanks guys I hadn't check for a data sheet as i thought it was a fairly obscure part, but seems readily available \$\endgroup\$
    – andrew
    Sep 26, 2016 at 15:14
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    \$\begingroup\$ Rule 1: always check for a datasheet. Rule 2: if you can't find a datasheet, buy something else ;) \$\endgroup\$
    – marcelm
    Sep 26, 2016 at 15:21

2 Answers 2

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Yes, what you propose is correct. These transformers can be used selecting a serial wiring for 230 V AC or in parallel for 115 V AC. Please make sure to connect the 115V connection to the 0 connection on the other winding. You will remain with one free 0 and one free 115 V connection. The free connection can be wired to the live 230V and the 0 to the neutral.

The same principle is valid for two of the 9 V AC windings. Both parallel and serial connections are possible. If you need more current on the 9V side, then you can put the windings in parallel. If you need 18 V on the secondary side, then you can put them in series.

Note: I want to remind you that working with systems connected to mains voltages can be dangerous.

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From page 5 of the data sheet which can be found here.

enter image description here

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  • \$\begingroup\$ The data sheet offers some very high quality schematics for parallel and serial connection of primary and secondary windings. Even the different colours of the connections are explained. I wish data sheets of that quality were available from all manufacturers. \$\endgroup\$
    – Uwe
    Sep 27, 2016 at 7:03

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