110v transformer

[Coco199]

Installing a wall mounted transformer.

Single phase with 2 x 16 amp sockets

Input connections are 240v 220v 0v 10v

Output/secondary side 55v 0v 55v

Whay would the connections regarding the input/primary side live neutral earth.

The 10v is throwing me off

 

[brianmoooore]

The 10 volt tap is 'fine tuning' for the output voltage. Use whichever one gives closest to 110 V output.
Live in goes to 220 or 240 and neutral in goes to 0 or 10.

 

[snowhead]

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With the 10v (effectively -10v) you can get inputs of;

0v and 220v = 220v
10v and 220v = 230v
0v and 240v = 240v
10v and 140v = 250v

As per Brian, to trim the 55 0 55 to 110v, depending on the available input voltage.

 

[Lucien Nunes]

What they ^^ said, to accommodate various mains voltages. Note that the tapping should be chosen on the basis of the actual mains voltage, not adjusted to put the output voltage 'right' when off load, because the voltage will fall by the regulation percentage once full load is applied. For example, on 230V mains you might find the output closer to 55-0-55 using the 240+0 taps rather than 220+10, if measured off load. But on load the voltage would fall, possibly out of spec. If the mains is 230V use 220+10.

 

[brianmoooore]

All mains voltage is declared as 230 volts, and a few years ago it was declared as 240 volts, but no actual changes were made.
Definitely measure the output voltage under load, but don't assume that 220 + 10 are the correct taps, just because the DNO say so.
My own supplies are normally around the 245 volt area.

 

[Simon47]

I also normally see 240V+. The DNOs like to keep it as high as they can (without going over the upper limit of course) as that minimises I2R losses and maximises the capacity of the network. But things have changed somewhat with the level of embedded generation (mostly solar PV) and I suspect quite a few final substation taps have had to be changed where changed/reversed power flows have resulted in higher end user voltages (probably coming to light as a result of the owners of the new PV installs complaining that their inverters trip out on very sunny days).