transformer question

[KCC]

Hi,

I recently dug out an old transformer and am thinking to use it on new projects. This thing has four tabs for connecting to AC main. It labels
" 0 100 0 100 " . Anyone knows how to wire this to AC main?

Peter

[peranders]

If the two windings are separate you can either connect them in series (=200V in) or in parallel (=100 V in). Be careful though if you aren't sure about the polarity of the windings.

Wrong connection -> smoke if you don't have low rated fuses between the mains and the transformer.

[e96mlo]

Since the primary voltage is rated for 200 V and you probably have 230 V or 240 V in the outlet, you will have a higher secondary voltage than stated on the transformer. Just so you don't blow any expensive components.

/Marcus

[peranders]

I forgot to say that's really important that you don't exceed the voltage rating. The transformer gets hot immediatly and self destruct eventually.

Why? The iron saturates and the inductance get reduced to nothing and only the internal resistance determine the current through the primary windings.

[e96mlo]

Depending on size and core material different transformers have more or less capability to withstand overvoltage. Or am I wrong here?

When I start to think of it I'm not so sure anymore...

/Marcus

[KCC]

Thanks to peranders and e96mlo for your replys. I appreciated much to your valuable opinions. Well,I think I've solved the mystery with your helps. I am located here in Canada so my ac outlet is 105v. The transformer is center tapped with +/- 28v output.I wired the thing in parallel. At first,I could not get any readings from my multimeter.The digits just kept blinking. So I was stuck for a while. Later I decided to wire the whole power supply up with bridge rectifier and capacitors.Then I connected the power supply to a power amp together with tuner and preamp and a cheap speaker. And,bingo! It worked.I since listened to the radio for hours without any misbehaviours of the power supply.

And,yes,I did use the variac - a dear lesson learned a couple years ago when I witnessed a small atomic bomb blew up in front of my very eyes(followed by fire and smoke and someone upstairs screamed to call 911) as I plugging in my newly wired(translate:expensive) power amp into the ac outlet.And I was certain that I wired it correctly as I've done these so many times without incidents.

Thanks again!