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transformer getting too hot.


aimans
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i was using a 1500mA, 12V transformer to find the resonance frequency of a copper wire. but the transformer was getting hot too quickly, within 15mins of its running it was too hot to touch. is it because the circuit was short circuited by directly connecting to the copper wire with nothing else? or is there a problem with the transformer?

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i was using a 1500mA, 12V transformer to find the resonance frequency of a copper wire. but the transformer was getting hot too quickly, within 15mins of its running it was too hot to touch. is it because the circuit was short circuited by directly connecting to the copper wire with nothing else? or is there a problem with the transformer?


Can you post a picture of the circuit?
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You were doing what?? You can't connect a wire across a transformer winding... that is a short. Yes, a transformer will get hot if you short it's winding.

Tell us a bit more about...

... find the resonance frequency of a copper wire.


Resonance with what? Self resonance? How are you changing the frequency? At best wire "looks like" a series RL... wire is about 20nH/inch and the wire resistance is very small. You could calculate the frequence where XL=R
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wow I didn't read that first post properly, you can short circuit the seconday of a transformer for testing purposes but you have to be really careful about the current getting too high.

However I have only ever heard of short circuiting a transformers secondary to find copper losses in the transformer.



What were you trying to test? The resonant frequency of a wire?

12088.png

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Yes... but there is no "C" here. It's a series RL circuit.

You short windings of a transformer to measure leakage inductance, but the transformer isn't active. To measure the leakage inductance of a winding, short ALL other windings and measure the L of the winding of interest on a bridge at the frequency the transformer operates... repeat for each winding. I don't see how shorting a winding will help you find copper loss. You need to know either the RMS voltage or current across the winding to do that. To take into consideration higher order affects, the temperature is needed as well as it can/will change the resistance.

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i was trying to determine the frequency of the a.c[ i know it is about 50-60Hz] but wanted to find it myself, and also to find the number of harmonics in a fixed length and mass[i got upto the 3rd harmonic at max. with .9m and .15kg]so i simply shorted it out, the thing got so hot that the plastic on which the windings were made melted, even though the room temperature was close to 0` Celcius.

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If you short circuit a voltage supply without something to limit the current then it gets too hot. Hopefully it is a fuse that gets too hot and it blows to prevent a fire.
Keep away from electrical things until you learn the basics.

The mains frequency in my country is 60Hz. It is 50Hz in some other countries. You can't change it. It is easily measured with a frequency counter. My multimeter has a very accurate frequency counter.

The harmonics are caused by distortion, not by length and not by weight.

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i was trying to determine the frequency of the a.c[ i know it is about 50-60Hz] but wanted to find it myself,


The easiest way to do that is to use an oscilloscope, measure the number of divisions between the start and the finish of one sine wave. Multiply that by the S/div and invert :)


and also to find the number of harmonics in a fixed length and mass[i got up to the 3rd harmonic at max. with .9m and .15kg]so i simply shorted it out, the thing got so hot that the plastic on which the windings were made melted, even though the room temperature was close to 0` Celsius.


This doesn't make any sense, there will only be harmonics present if the load is non-linear. Even if there were any harmonics, the only way to "short" them out is to tune a filter circuit to the frequency of the harmonic, it will then act like a short to those frequencies. Even then, the filter exists between line and ground, not a dead short between the terminals.

Shorting out the transformer's secondary with a wire is a sure way to set your transformer on fire.
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If you short circuit a voltage supply without something to limit the current then it gets too hot. Hopefully it is a fuse that gets too hot and it blows to prevent a fire.
Keep away from electrical things until you learn the basics.

The mains frequency in my country is 60Hz. It is 50Hz in some other countries. You can't change it. It is easily measured with a frequency counter. My multimeter has a very accurate frequency counter.

The harmonics are caused by distortion, not by length and not by weight.


i knew these methods as well, but wanted to implement my theory stuff.

and the harmonics[or loops] in  the stationary wave were caused by keeping a horse shoe magnet at the middle of the wire, so that the wire was inside a perpendicular magnetic field. and when i passed the current from the transformer it vibrated with 3 loops or harmonics.

the loops which are formed in the stationary wave are linked to the length of the wire and the tension in it[hanged mass from a pulley], the equation for the  frequency of the fundamental mode in a stretched wire is below:

T=tension in wire
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AC current through wire that passes through a unknown flux field gives you the frequency based on the number of loops you see?? I've never heard of such a thing... please explain further!!

Are you sure your just not seeing the resonant frequency of the wire... like a guitar string?


here the below files may espolain what i was trying to do, the site does not allow .swf files so i put em in a zip folder,
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