Transformer continuity

SimpleSimon · Feb 13, 2011

Thought I was doing the right Thing but now I'm not so sure.
Continuity of a light fitting transformer. If using a basic multimeter, I test continuity of live between the supply side and load side of a transformer, would I expect a reading? Or is it a no because it is only by induction when live the circuit is formed.

johnboy6083 · Feb 13, 2011

if you want to check the windings are good, then you want to test the Live and neutral on the primary and the same on the secondary. you should have a high resistance. if its very low, then the windings are probably shot

Chr!s · Feb 13, 2011

Thought I was doing the right Thing but now I'm not so sure.
Continuity of a light fitting transformer. If using a basic multimeter, I test continuity of live between the supply side and load side of a transformer, would I expect a reading? Or is it a no because it is only by induction when live the circuit is formed.

You will probably have an electronic transformer which uses switching to achieve a required voltage

telectrix · Feb 13, 2011

on a normal 230/12 tranny, you will get a cont. reading across the primary and across the secondary. the primary will be the higher of the 2. electronic ones may not give a reading and can only be checked by applying 230v to the primary and seeing if you get 12v on the sec.

RogertheBodger · Feb 13, 2011

Yes the Primary coil induces a voltage in the secondary coil, but they are Electrically seperate, you should get a reading through both coils but not between.

johnboy6083 · Feb 13, 2011

i assumed that you were talking about a normal inductive tranny, not a switchmode powers supply.

SimpleSimon · Feb 13, 2011

RogertheBodger said:
Yes the Primary coil induces a voltage in the secondary coil, but they are Electrically seperate, you should get a reading through both coils but not between.

This is what I thought.
Checjing kitchen light in my house cause it tripped RCBO last night when switched on, came to it today and all wires are fine so went to go to turn it on to see if it still tripped and it didn't trip the RCBO. Lights didn't come on however so got me thinking that the trannys gone (cheap horrible IKEA one) checked basic continuity across the primary and secondary and got nothing so assumed it was that. Now I've walked away it got me realising that I did it wrong.
Johnnyboy that's what I need to do is check the resistance between the windings. Thanks.
I won't be doing that though cause I've chucked the ugly thing n it gives me an excuse to get a new one.