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filholder 22nd March 2006 11:39 PM

Transformer issue
 
HI,

Sorry if this sounds stupid but what exactlly am i doing wrong, I am trying to test the voltage ouput of some transformers i recent found. They are rated as 43v secondaries and have 2x 120v primaries. Since the output volatge would be too high instead of running the primaries after each other to make a normal 240 input i have been trying to run them in parraell,.

The issue is i cannot test even one of the units, I plug one in with nothing attached and it blows the 13a mains fuse, i then though maybe it needs some load the other end so i rigged up a bridge rectifer and with 1 ohm 5 watt resistors on the output ( read somewhere this stops in rush current blowing fuses) going into a big capacitor.

Flick switch again, transformer humms for a couple of seconds and then the bloody 13 a fuse goes again.

They are bg transfomers have no VA rating but they weight 3 kilos each, any ideas on how i can get the thing up long enough to do some tests.

phil

davidlzimmer 23rd March 2006 01:56 AM

I'm not positive about what you a saying but, I would think you would wire in parallel for 120 and series for 240.

paulb 23rd March 2006 03:09 AM

Quote:

Originally posted by davidlzimmer
I'm not positive about what you a saying but, I would think you would wire in parallel for 120 and series for 240.
Yup. You have 2x120 volt primaries and are running from 240, putting them in series is your only choice. You are stuck with the 43 volts on the secondary.

slowhands 23rd March 2006 03:13 AM

Re: Transformer issue
 
Quote:

Originally posted by filholder

HI,

I am trying to test the voltage ouput of some transformers i recent found. They are rated as 43v secondaries and have 2x 120v primaries. Since the output volatge would be too high instead of running the primaries after each other to make a normal 240 input i have been trying to run them in parraell,.
phil

You must use the primaries in series. You cannot wire them in parallel without saturating the core and burning up the transformer. Don't even try.
Quote:

Originally posted by filholder

The issue is i cannot test even one of the units, I plug one in with nothing attached and it blows the 13a mains fuse, i then though maybe it needs some load the other end so i rigged up a bridge rectifer and with 1 ohm 5 watt resistors on the output ( read somewhere this stops in rush current blowing fuses) going into a big capacitor.

Flick switch again, transformer humms for a couple of seconds and then the bloody 13 a fuse goes again.

They are bg transfomers have no VA rating but they weight 3 kilos each, any ideas on how i can get the thing up long enough to do some tests.

phil

It is fortunate the fuses blew, rather than burning out the wires. The transformer cannot be used with the primaries in parallel on 240 volt, 50Hz. Test it with primaries in series. If the secondary voltage is too high, sorry, get another transformer with lower voltages.

davidlzimmer 23rd March 2006 03:18 AM

OK, I gotta ask!

How do you guys get those quotes in the boxes???

I've never been able to figure it out!

If it had wires I'd have a better chance!

theChris 23rd March 2006 03:22 AM

let me try to get it out of a box:

\[quote\]
text in the box
\[/quote\]

if you see \ chars there, just remove them. i have no idea if phpbbb supports escaping of things.

alternatively, click on the quote or list buttons.

davidlzimmer 23rd March 2006 03:30 AM

\[quote\]
if you see \ chars there, just remove them. i have no idea if phpbbb supports escaping of things.
\[/quote\]

Let's see....

Bazukaz 23rd March 2006 03:30 AM

I think wiring primaries of both transformers in series(with each trafo's primaries wired in series too) could be a possibility to reduce output voltage twice.The ouput power would probably decrease.

davidlzimmer 23rd March 2006 03:32 AM

Scr_w it! :-)

davidlzimmer 23rd March 2006 03:34 AM

How bout each in parrallel then sereised?


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