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It is currently 15 Dec 2019, 18:43

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 Post subject: Transformer question
PostPosted: 07 Apr 2019, 03:12 
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Joined: 01 Jun 2013, 09:05
Posts: 860
Here is a stupid question but I need to ask.

I have never done this because I have always had marked up Tx's.

Looking at a dual voltage transformer where you can wire the primary for 115V dual parallel windings or dual series for 240V.
The windings have a dot designation for phase polarity. However I have an un-marked transformer.

OK I know you can inject AC voltage into the secondary and compare the two primary outputs with a scope for phase.

However this is not possible out in the field at the moment. So does anyone know if the primary windings are connected in series but out of phase will I just get no secondary voltage or will the primary current be excessive due to magnetic field cancelation and burn out the transformer primary winding?

I guess I could trash a small Tx and see what happens... :| . Its something I have never seen.
Obviously its a 50/50 chance of being correct or wrong on first power up.

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M. Gregg

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 Post subject: Re: Transformer question
PostPosted: 07 Apr 2019, 09:02 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi, A problem for sure. If you bring a signal generator type device or even something like a phone that will put out a signal you can use it to measure the output of the transformer. One way it will work and one way will give near zero output. Feed the signal into the primaries and measure the output on the secondaries. Since the impedance of the transformer primaries are likely to be fairly high no harm will come to the device providing the signal. It will require a sensitive meter to measure the secondaries though. If it has low voltage secondaries (and is not in circuit) you can feed the signal into the secondary and measure the primaries to see which way is series additive and which is not. Otherwise at 50-50 you are likely to get smoke half the time.

Good listening
Bruce

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 Post subject: Re: Transformer question
PostPosted: 07 Apr 2019, 14:24 
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gofar99 wrote:
Hi, A problem for sure. If it has low voltage secondaries (and is not in circuit) you can feed the signal into the secondary and measure the primaries to see which way is series additive and which is not. Otherwise at 50-50 you are likely to get smoke half the time.

Good listening
Bruce


Hi Bruce,

I'll give it a try input to secondary and look at the output voltage primary (audio or sine).
Thanks for the reply :) so much going on at the moment.


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M. Gregg

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