I'm re-using transformers...

~

~misfit~ 9 years ago

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)

Vote

I

Ian Field 9 years ago

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

Vote

~

~misfit~ 9 years ago

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)

Vote

P

Phil Allison 9 years ago

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

** 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

Vote

P

Phil Allison 9 years ago

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

** If wrong, the lamp will light brightly.

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

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

..... Phil

Vote

~

~misfit~ 9 years ago

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)

Vote

I

Ian Field 9 years ago

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

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

Vote

~

~misfit~ 9 years ago

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)

Vote

P

Phil Allison 9 years ago

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

** 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

Vote

I

Ian Field 9 years ago

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

Vote

I'm re-using transformers...

Join the Discussion

Didn't find your answer?