Transformer question/ issue

Paul Frost

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Dec 25, 2015
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4,530
im no electrician so yeah...
when i connect a transformer to my 240V plug it just gets short circuted, no wires are touching, and nothing is connected to the output, and the way it works is confusing, i am basicly creating a short circut, how does it even work ? i mean like you connect 1 side of the wire, loop it around a metal core, and connect the other side back to the plug, how the hell should that work ? :??:
 
Solution


There could be two reasons - 1. There is a short somewhere, 2. The design of the transformer is improper.

Every computer PSU has a transformer inside that converts the AC voltage (110, 220) to 12 Volts DC. It can be plugged in and left plugged in even when the computer is turned OFF and even when the PSU switch is turned OFF.
Coiled wire with an alternating current running through is the basic definition of an inductor. An inductor generates a magnetic field. In the transformer a magnetic field is created in the iron core. A collapsing magnetic field introduces current on the secondary side of the transformer. The number of windings determine the voltage change. An inductor is NOT a short and on a transformer with an open secondary winding it will be very difficult for current to flow.

Http://lmgtfy.com/?q=How+does+a+transformer+work

If you're flipping a breaker when you plug it in there a short in the transformer or you are hooking it up wrong. Or plugging it in to DC
 

Paul Frost

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Dec 25, 2015
42
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4,530
do i need to have a load on the output ? or on the input ? because i dont have any load, or measuring devices such as volt meters/amp meters
i read the wiki page.... the basic stuff
 


The output side does not need a load. When a load is applied the transformer will supply the designed voltage and amps.
 


There could be two reasons - 1. There is a short somewhere, 2. The design of the transformer is improper.

Every computer PSU has a transformer inside that converts the AC voltage (110, 220) to 12 Volts DC. It can be plugged in and left plugged in even when the computer is turned OFF and even when the PSU switch is turned OFF.
 
Solution


This design information I do not know. An electrical engineer should be in a position to answer this. Taking the power factor into consideration, the transformer should be designed for 60 watts, even though 14.5 X 3 = 43.5 watts.
 

makkem

Distinguished
Hi
Point one ; did you use enamelled wire for the winding,this is essential.
Point two ; You need to know the resistance per meter of the enamelled wire this enables you to calculate the length you need in order not to short out the power.For instance if the resistance is 10 ohms on 240V you will get 24A which will blow your fuse.
Point Three ; You need to know a lot of electrical theory to design and wind your own transformers ,you need to calculate resistances and inductances and determine winding ratios ,number of windings and gauge of wires.to try this with insufficient knowledge,especially with 240V can be very dangerous and can be a fire risk,it will also likely cost you more than buying one .
Best advice has to be Buy one.
 

makkem

Distinguished
Ah,right.
The problem you are having is that the transformers in SMPS are used in a different way(try googling switch mode circuit) in that they are not connected live to neutral but are effectively in series with the load and as such have a very low coil resistance ,much lower than a standard transformer and as such cannot be used as such .
It is that low coil resistance that is causing your problems .
Your multimeter will beep if the resistance is below a certain value and as such will depend on how the manufacturer has set it up,but with a conventional transformer it would not beep as the resistance would be quite high but with that transformer I would think that it would beep.