I'm re-using transformers...

Once upon a time on usenet Ian Field wrote:
"~misfit~" <shaun.at.pukekohe@gmail.com> wrote in message
news:eek:hqll7$krj$1@dont-email.me...
Once upon a time on usenet Phil Allison wrote:
~misfit~ wrote:

-----------------


Phil quick question (as I can't readily find the answer right now).

Can I use a transformer with the primary side described as 'double
120v 50/60Hz' on 240v by running the two primaries in series?




** Errr - that is how it is meant to be used.

I thought so as it makes sense but I haven't read that anywhere and
the site selling them doesn't say that.

In parallel for 120VAC, in series for 240VAC.

Makes sense.

You WILL need a to get the phasing right, hopefully the units are
marked or you have an info sheet showing which wire colours to join.

Hopefully. I haven't ordered yet but AliExpress isn't known for
giving out lots of info. :-/

Series won't do anything if you get the phase wrong. Power up
parallel with a light bulb in series to limit the current in case you
got it wrong.
Click to expand...

Thanks. I'll screw a batten fitting to a piece of wood, been meaning to do
that for a while. I knew there was a reason to keep a few old incandescant
bulbs...

I've got quite a few saved transformers and have been connecting up the ones
that I know the primaries are 240v but am having trouble working out what's
going on with secondaries where there are multiples. I'm getting AC volts
readings between secondary wires that, when tested for resistance (not
powered up) don't appear to be connected. I'm guessing capacitive coupling
maybe? Was thinking putting a light bulb for a load might give me a better
idea of what's going on.

I have a nice little (~50VA) toroidial that is obviously 'double 120v' as
two primary wires are soldered together and have heatshrink over them. (I
removed it and tested resistance and it reads like a centre-tapped winding.)
However it's got four secondary wires and I'm damned if I can make sense of
whats's going on just with the meter. (Tested for resistance unpowered then
AC volts when powered up.) I'm hoping loading them will help.

Cheers,
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)
 
"Phil Allison" <pallison49@gmail.com> wrote in message
news:72972ad8-b75e-4360-94ca-efae71c64c90@googlegroups.com...
Ian Field wrote:

--------------------



** Errr - that is how it is meant to be used.

In parallel for 120VAC, in series for 240VAC.

You WILL need a to get the phasing right, hopefully the units are
marked
or you have an info sheet showing which wire colours to join.


In series - wrong phasing just doesn't work.

In parallel - wrong phasing lets the magic smoke out.


** Nonsense, the situations are both the same.

One half of the primary is trying to magnetise the core in the opposite
direction to the other. So the core does not magnetise, there is no back
emf - leaving only the resistance of the windings.
Click to expand...

Are you saying that series out of phase primaries *DOES* work - or parallel
out of phase primaries *ISN'T* destructive?
 
Once upon a time on usenet Ian Field wrote:
"Phil Allison" <pallison49@gmail.com> wrote in message
news:72972ad8-b75e-4360-94ca-efae71c64c90@googlegroups.com...
Ian Field wrote:

--------------------



** Errr - that is how it is meant to be used.

In parallel for 120VAC, in series for 240VAC.

You WILL need a to get the phasing right, hopefully the units are
marked
or you have an info sheet showing which wire colours to join.


In series - wrong phasing just doesn't work.

In parallel - wrong phasing lets the magic smoke out.


** Nonsense, the situations are both the same.

One half of the primary is trying to magnetise the core in the
opposite direction to the other. So the core does not magnetise,
there is no back emf - leaving only the resistance of the windings.

Are you saying that series out of phase primaries *DOES* work - or
parallel out of phase primaries *ISN'T* destructive?
Click to expand...

So the question must be is there a way to tell if you've got it wrong? If I
wire a lamp in series with it what would happen if it were wrong - or right?
Is the wattage of the lamp important considering I'm wanting to test some
quite small transformers (>50VA) as well as larger ones.

Thanks,
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)
 
Ian Field wrote:

-------------------

In series - wrong phasing just doesn't work.

In parallel - wrong phasing lets the magic smoke out.


** Nonsense, the situations are both the same.

One half of the primary is trying to magnetise the core in the opposite
direction to the other. So the core does not magnetise, there is no back
emf - leaving only the resistance of the windings.


Are you saying that series out of phase primaries *DOES* work - or parallel
out of phase primaries *ISN'T* destructive?
Click to expand...

** In both cases the transformer will not work and will be destroyed by overheating unless a fuse blows.

In order to function, the core must magnetise at supply frequency.


...... Phil
 
~misfit~ wrote:

---------------------
So the question must be is there a way to tell if you've got it wrong? If I
wire a lamp in series with it what would happen if it were wrong - or right?
Click to expand...

** If wrong, the lamp will light brightly.

Otherwise faintly or not at all and your secondary voltages are there.

Is the wattage of the lamp important considering I'm wanting to test some
quite small transformers (>50VA) as well as larger ones.
Click to expand...

** A 40 to 60W lamp, NOT CFL or LED is good.



...... Phil
 
Once upon a time on usenet Phil Allison wrote:
~misfit~ wrote:

---------------------

So the question must be is there a way to tell if you've got it
wrong? If I wire a lamp in series with it what would happen if it
were wrong - or right?



** If wrong, the lamp will light brightly.

Otherwise faintly or not at all and your secondary voltages are
there.

Is the wattage of the lamp important considering I'm wanting to test
some quite small transformers (>50VA) as well as larger ones.



** A 40 to 60W lamp, NOT CFL or LED is good.
Click to expand...

Thanks Phil, I've saved a few incandescant bulbs. It's good to have a use
for one again. ;)
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)
 
"Phil Allison" <pallison49@gmail.com> wrote in message
news:86b18eb3-9d5c-46cb-a305-d3a8806a0738@googlegroups.com...
Ian Field wrote:

-------------------


In series - wrong phasing just doesn't work.

In parallel - wrong phasing lets the magic smoke out.


** Nonsense, the situations are both the same.

One half of the primary is trying to magnetise the core in the opposite
direction to the other. So the core does not magnetise, there is no
back
emf - leaving only the resistance of the windings.


Are you saying that series out of phase primaries *DOES* work - or
parallel
out of phase primaries *ISN'T* destructive?


** In both cases the transformer will not work and will be destroyed by
overheating unless a fuse blows.

In order to function, the core must magnetise at supply frequency.
Click to expand...

So why do some manufacturers add anti-phase bucking windings to primaries?

AFAIK: Its something to do with controlling leakage inductance, but beyond
that...............
 
Once upon a time on usenet Ian Field wrote:
"Phil Allison" <pallison49@gmail.com> wrote in message
news:86b18eb3-9d5c-46cb-a305-d3a8806a0738@googlegroups.com...
Ian Field wrote:

-------------------


In series - wrong phasing just doesn't work.

In parallel - wrong phasing lets the magic smoke out.


** Nonsense, the situations are both the same.

One half of the primary is trying to magnetise the core in the
opposite direction to the other. So the core does not magnetise,
there is no back
emf - leaving only the resistance of the windings.


Are you saying that series out of phase primaries *DOES* work - or
parallel
out of phase primaries *ISN'T* destructive?


** In both cases the transformer will not work and will be destroyed
by overheating unless a fuse blows.

In order to function, the core must magnetise at supply frequency.

So why do some manufacturers add anti-phase bucking windings to
primaries?
AFAIK: Its something to do with controlling leakage inductance, but
beyond that...............
Click to expand...

Gah! Please don't say things like that, I'm on a steep learning curve as it
is! ;-)
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)
 
Ian Field wrote:

-------------------


** In both cases the transformer will not work and will be destroyed by
overheating unless a fuse blows.

In order to function, the core must magnetise at supply frequency.


So why do some manufacturers add anti-phase bucking windings to primaries?

AFAIK: Its something to do with controlling leakage inductance, but beyond
that...............
Click to expand...

** So your reply to the OP was based on guesswork.

You had no hands on experience and you did not look it up.

Brilliant.



....... Phil
 
"Phil Allison" <pallison49@gmail.com> wrote in message
news:f1417a53-b1da-42aa-b59c-3d4caa3b7016@googlegroups.com...
Ian Field wrote:

-------------------



** In both cases the transformer will not work and will be destroyed by
overheating unless a fuse blows.

In order to function, the core must magnetise at supply frequency.


So why do some manufacturers add anti-phase bucking windings to
primaries?

AFAIK: Its something to do with controlling leakage inductance, but
beyond
that...............



** So your reply to the OP was based on guesswork.

You had no hands on experience and you did not look it up.
Click to expand...

Knowing that anti phase series primaries don't work wasn't a guess.
 
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