Which coil of a transformer should I connect to 220V?

• Feb 28, 2007

• #1

jhanus

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Hello,

I found a transformer with cutoff wires, I want to use it , but primary coil has 3 leads:
red, blue and brown. So which pair to connect to 220V?

Resistance between are as on picture.

Why are there 3 leads, none is connected to the iron core.

Thanks.

 

• Feb 28, 2007

• #2

D

dkace

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Re: Transformer question

maybe the third one is for tapping. How big the transformer is?

Try putting voltages starting from 24V upwards to see the outcome. Where was this Tr before implemented? There is no indication what so ever ?

Can you upload a photo or something?

D.

 

• Feb 28, 2007

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E-design

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Re: Transformer question

It looks like the transformer has a 240V with a tap for the 220V winding as well:

Blue - Brown (220V)
Blue - Red (240V)

 

• Feb 28, 2007

• #4

jhanus

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Re: Transformer question

Thanks,

Transformer was implemented in some old radio or tv.
Why should 220-240V make difference, when our 220 V output can oscillate from 210 to 230V.


Picture:

https://obrazki.elektroda.pl/52_1172675883.JPG

 

• Feb 28, 2007

• #5

E-design

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Re: Transformer question

Manufacturers often provide this 240V winding to accomodate countries that use 240V mains.

 

• Feb 28, 2007

• #6

D

dkace

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Re: Transformer question

It is either 220 to 24 or 220 to 9V just check it by applying a voltage of 220V and measure the output. I don't know anything about the tap so i second what E-design is saying . But just to be sure, just run a measurement.

D.

 

• Feb 28, 2007

• #7

jhanus

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Re: Transformer question

Haha, thank you all.

You just saved me a fuse or a transformer!, because I wanted to connect red-brown.

Just like E-design said:

E-design said:

It looks like the transformer has a 240V with a tap for the 220V winding as well:

Blue - Brown (220V)
Blue - Red (240V)

Click to expand...

-input 220V(Blue - Brown), output is 28V and (-18 )-0-18

But I don't know what is max. current or nominal, how to calculate that?!

 

• Feb 28, 2007

• #8

E-design

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Re: Transformer question

By the looks of it I would think 35VA to 50VA max.

 

• Feb 28, 2007

• #9

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dkace

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Re: Transformer question

I agree! normally these transformers output 35-50VA. What do you want to operate?

D.

 

• Feb 28, 2007

• #10

jhanus

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Re: Transformer question

I need power source like laboratory panel.

So I would use it for variety things(motors, stepper, Op-Amp, uC, ...).

When you say 35VA is this equal to output of:
- 35V and 1A
- 17.5V and 2A

 

• Mar 1, 2007

• #11

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dkace

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Re: Transformer question

Try this link


I think you will get a full answer...

D.

 

• Mar 1, 2007

• #12

jhanus

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Re: Transformer question

Thanks for help.

 

• Mar 2, 2007

• #13

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wisepie

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Re: Transformer question

Another estimation can be made is to check the copper wire size. Normally current density of 3 ~ 5 A/mm2 will be applied.