Transformer winding phase test????

[zebra50]

Hi!
I know we've had a lot of transformer/inductance questions recently but I don't think this has been covered.

I want to verify (or otherwise) an assumption that I made, or a conclusion to which I have leapt, about the phase of transformer widnings

Imagine that I have a transformer with 2 primaries and 2 secondaries. The primaries have inductance of 1H each. I can wire them in series two ways - one gives me 4H and one gives me zero Henries.

Am I right in assuming that the method that gives me greatest inductance is necessarily when the primaries are wound in the same direction and therefore are in phase? This would be nice because it gives a very quick way to confirm phase without getting the signal generator out.

Or are there situations when this is not true?

Taking this a bit further -if the above is true, is there a similar rule between the primary and secondary? i.e. can we connect a 'primary' and 'secondary' in series and deduce something about phase from their added inductance?

Many thanks

Stewart

 

[Moby]

Maybe i know something about, but i know that CJ and PRR are real experts for this. So, lets wait :wink:

 

[Guest]

[quote author="zebra50"]Imagine that I have a transformer with 2 primaries and 2 secondaries. The primaries have inductance of 1H each. I can wire them in series two ways - one gives me 4H and one gives me zero Henries.
[/quote]
Exactly, but for "Zero Henries" you loose properties of transformer.
Transformer band span ratio is function of ratio of shunt inductance
and leak {series} inductance.
In Si-iron transformer it is order of 100, in mumetals order of 1000 - 10 000.
AND IN YOUR TRANSFORMER WITH ANTISERIES PRIMARY IT IS ORDER OF 1.
this can perform as Tesla transformer. At first: ommit core. It does nothing.
[quote author="zebra50"]
can we connect a 'primary' and 'secondary' in series and deduce something about phase from their added inductance?
[/quote]
Yes, in 1:1 transformers it can be quick method to check relative
phase {+1 or -1} of primary/secondary connection.
Simply connect secondary to primary in phase series - measure big inductance.
Then connect secondary {with wires in reverse order} to primary
-measure small inductance.
xvlk
P.S.: with wounding connected paralel, results can not be as pretty, because of resistances.

 

[gyraf]

I check for winding phase by shorting my test oscillator with a diode - that gives a nice, asymetrical wave shape that is easily checked with a scope..

Jakob E.

 

[SSLtech]

[quote author="gyraf"]I check for winding phase by shorting my test oscillator with a diode - that gives a nice, asymetrical wave shape that is easily checked with a scope..[/quote]
Genius!

Keith

 

[zebra50]

Definitely a good tip.


Thanks to all. :wink:

 

[NewYorkDave]

A variation on that, which is a little kinder to your oscillator, is to insert a diode in series with the signal, acting as a half-wave rectifier.

This is an old-but-good test that I saw in a Crowhurst book from the '50s.

 

[Guest]

[quote author="gyraf"]I check for winding phase by shorting my test oscillator with a diode - that gives a nice, asymetrical wave shape that is easily checked with a scope..[/quote]
Or one diode paralel to primary, one paralel to secondary
and ear to analyze.

xvlk