I have a power transformer that I am trying to figure out if it works or not. It has the following listed on the input side

1  |  
2  |
3  |
4  |
5  |  240v
6  |  230v
7  |  220v
8  |  210v
9  |  0v
10 |
11 |
12 |

I am in the UK and use 240 mains, I have a mains cable with an inline fuse. How should I wire the input up?

  • 2
    \$\begingroup\$ In series with a suitable rated fuse and between "0v" and "240v". \$\endgroup\$
    – winny
    Apr 6, 2017 at 10:22

1 Answer 1


As winny commented,

Connect blue (neutral) to the "0v" connection.

Connect brown (line/live/hot) to the "240v" connection.

Your nominal 240V supply is actually now a nominal 230V +10%/-5%. So your local electrical utility can supply you with any voltage between 218.5V and 253V.

Last time I measured mine it was 237V but it varies a bit from day to day. The "240v" connection is a good one to choose if you are unsure.

It would be prudent to reduce the size of your fuse to the lowest value needed to support the load (load current * load voltage / supply voltage)


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