Transformer help!

[audiohed]

I have acquired a transformer which is 120/240 capable- 2 white and 2 green inputs, wht. wht. grn. grn. in that order. How should I wire for 120? I get continuity 1 and 4, with 2 and 3 jumpered.

[pieter t]

Can you measure inductance?

[Mooly]

You would normally connect the windings in parallel for 120 volt and in series for 240 volt operation.

The 'difficulty' comes from having to get the windings phased correctly.

1/ Identify the two separate windings via a simple continuity check. Each winding should have no continuity to the other.

2/ So first separate and then pick any wire of the four and check for continuity to the other three. You should find the wire you picked reads to just one of the others. Those two make one winding so label them clearly as a pair.

3/ The wires left should also make a similar pair with continuity. That is the second winding. Again label them as a pair.

4/ There should be NO continuity between the two pairs.

5/ Now we wire and test it safely by using a DBT (dim bulb tester) which is simply a domestic 60 or 100 watt mains filament bulb that you connect IN SERIES with the incoming mains. A lower wattage bulb is fine to.

6/ Connect one winding to the incoming supply via the bulb. The bulb acts to limit current in the event the windings are incorrectly wired and as a bonus illuminates to warn you.

7/ Connect the other winding in parallel. (If the wires in each pair were white and green then connect green to green and white to white in parallel).

8/ Switch on and confirm the output voltages are correct. The bulb should not be illuminated (apart from an initial flash). If the bulb lights brightly then reverse the wires to one winding only.

Hope that helps, its two minutes of a job with the transformer in front of you

[AKSA]

Thank you Karl,

This is terffic advice.

Good luck, Audiohed!

Hugh