How to build transformer

Power transformers can get hot and that can cause problems with insulation. However, modern 'enamel' is really tough and 'wires' (actually rods) for power transformers are wound with glass fiber tapes that can stand more than 200C. Still larger transformers are immersed in oil. It is not uncommon to run transformers at 100C and nothing happens to the insulations or the transformer.

c_mitra said:

This is a very old value and is overly conservative. Modern transformers happily run at 100C and 30AWG copper wire will happily take 0.5A without fuss.

If you are selling to the Defense, then perhaps 150mA is fine!!

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Personally, I don't want my Transformer Running That HOT.
And Maybe, If you also don't care about CONSIDERABLE VARIATIONS IN VOLTAGE WITH LOAD.
But He is also wanting 1.5 AMPS output, Not 0.5 Amps!

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RITESH KAKKAR; said:

why how you calculate?

how to calculate its impedance.

i want to build Dc to Dc converter i am learning how core changes and other factor make transformer..

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Is this Transformer for a 12 VDC to 110 or 220 VAC Inverter?
Or is this Just a Step Down Transformer?
And at What Frequency? 50 or 60 Hz.?

chemelec said:

And Maybe, If you also don't care about CONSIDERABLE VARIATIONS IN VOLTAGE WITH LOAD.
But He is also wanting 1.5 AMPS output, Not 0.5 Amps!

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He just mentioned that he wanted to practice winding a transformer for 24V at 1.5A- he did not mention the input voltage or the frequency.

I would suggest him to go through the steps in a systematic way and perhaps use trifilar winding for the output to get about 1.5A current capacity.

I believe he has not got a fixed focus yet. He is perhaps just learning how to use the equations and formulae and learn the steps.

All transformers show considerable variations (in output voltage) with input voltage and output current (there are constant current and constant voltage transformers too) but we are not discussing that here.

If a person wants to learn the basic principles of a transformer by winding two coils on a iron nail, I do not have any objection.

I Also Don't object to winding coils on a Nail, for simple Tests.

And He DID Mention Making a DC to AC Inverter.

When I said about Voltage Variations, I didn't mean Constant Voltage.

However I have some CHEAP Chinese Transformers.
Rated 1 Amp at 12 Volts, and that is Correct.
However at 10 Ma Load, they are 19 Volts out.
I Don't consider that as being a good transformer.
Driving Some Circuits with this could result in burning out parts.

My better quality transformers are stable within 1 or 2 volts between full load and No Load.
I consider that as Acceptable.

My better quality transformers are stable within 1 or 2 volts between full load and No Load.
I consider that as Acceptable.

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You forgot to mention the prices of the two transformers- one you consider acceptable and the other one you do not consider acceptable.

I just looked around- I have 3 wall transformers that are written 12VAC 1A- and the no load voltage is 18V for all of them. They are all china made. All came as power adapters for various items.

It will cost only a little to add a rectifier, filter and a regulator. Much less than the price difference between the 'acceptable' and 'non-acceptable' brands of transformers.

I do not think I can get a 12VAC 1A secondary and 220V primary 50 Hz transformers that will have output stable within 1-2V between full and no load... they are simply not available here...

Problem is Regulating your Transformer to 12 Volts, Won't work properly.
As it gets pulled down to about 14.5 Volts, your Regular no longer regulates.

But Yes they are CHEAP to Buy and OK for some Applications.

In Canada here, I have Numerous Good transformer available.

Take Care.............

chemelec said:

Problem is Regulating your Transformer to 12 Volts, Won't work properly.
As it gets pulled down to about 14.5 Volts, your Regular no longer regulates..

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After rectification and adding a simple capacitor, the voltage goes up still higher. I do not think that I am overloading the output and I do not see that the regulator goes out of regulation. But the input side (at the capacitor) remains around 16V or so, and that is ok...

I made a power supply based on a 12.6 V transformer. It produces 16VDC, no load. Its voltage drops as I increase load.

Why are people guessing that Ritesh wants Regulated 12VDC when in post #9 he said, "i will try to make ac source of some 24V 1.5amp"? From a nail with some wire on it.