# Transformer phase check

#### superway

Joined Oct 19, 2009
125
Hello,
Can you help me this question?
I would like to check s transfomer inverter side and input 120V/240Vac side are in phase or out of phase. Would you please help me a short way to check it? or do we need to build any simple circuit to check this one?

Thanks a lot.

Ken

#### Bychon

Joined Mar 12, 2010
469
What is an s transformer? What kind of inverter does it connect to and how is it connected? Can you get it out of the circuit? Please explain slower.

#### superway

Joined Oct 19, 2009
125
The transformer 300VA. Input 120/240vac, the output is 60vac and the ratio inverter side is 8 Vac. I want to check to make sure the input 120/24vac and the inverter side 8vac are in-phase.

Thanks

#### Bychon

Joined Mar 12, 2010
469
Connect the 8 volt winding to one end of the 120/240 winding. Connect ac voltage to the 120/240 winding. Measure with volt meter to unconnected end of 8 v winding. If the voltage is higher than what you put in the 120/240 winding, it is in phase at that time. If the voltage is lower, it is out of phase.

#### R!f@@

Joined Apr 2, 2009
9,918
{ed - later}
I was asking the OP. not bychon. Sorry if you guys misunderstood me

U are not making any sense here, and we are having a hard time trying to understand you

{ed}
if you are talking about more than one output voltages from a transformer, then all outputs are always in phase.

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#### t_n_k

Joined Mar 6, 2009
5,455
if you are talking about more than one output voltages from a transformer, then all outputs are always in phase.
Hi R!f@@,

We might be forgiven for arguing this doesn't seem to make sense either. Perhaps I haven't understood your meaning.

It's quite possible for secondary windings to be 180° out of phase depending upon how one measures the voltages across them. Connect the earth lead of a 2 channel CRO to the common point of a centre-tapped secondary and monitor the voltage at either end of the total winding on the two channels - there will normally be a 180° phase difference. Or perhaps connect two isolated secondary windings in series and you come up with two different voltages depending upon whether you connect them as phase adding or subtracting.

This is what is implicit in Bychon's suggested test.

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#### R!f@@

Joined Apr 2, 2009
9,918
Argument is correct tnk,

What I meant was normally it is wound in phase.

How you wire it is totally different.
What say u?

#### superway

Joined Oct 19, 2009
125
Connect the 8 volt winding to one end of the 120/240 winding. Connect ac voltage to the 120/240 winding. Measure with volt meter to unconnected end of 8 v winding. If the voltage is higher than what you put in the 120/240 winding, it is in phase at that time. If the voltage is lower, it is out of phase.
Hi Bychon,
Thanks. I understand what your explanation.
So, your theory is that added up 120v or 240vac to 8vac by series and if the voltage is higher then it is in phase, if it is lower then out of phase ?

#### Bychon

Joined Mar 12, 2010
469
That's what I said.