I was testing a transformer I had bought, and I tested the voltage at 30v, then i proceeded to test the current, I connected both of the outputs from the secondary to a 1 ohm 25watt resistor, that is one on each side, then I connected my meter to it. I got a reading of 3.2 amps, but then it just kept falling, when I disconnected it, it had gone down to 2.75 and was still going. Does that mean I connected it wrong, I dont see how it could be wrong, but I dont understand why the current was falling. Any help?
If you bought this transformer it should have a VA rating in other words a voltage x amps rating. This gives the maximum current on both primary and secondary Example if you bought a 300VA transformer with a 30Volt secondary the maximum current is 300/30 10 amps absolute maximum You then match the load so as not to exceed this value and also you install 10 amp fuses to protect the transformer from burning out. If you do not know the VA rating then start with a high value resistor or better still a potentiometer and slowly decrease the resistance whilst measuring the current until the transformer starts to get hot The load and ammeter should be in series not in parallel
from what you said i understand that to the two ends of the secondary you connected the two ends of the resistor and the two terminals of the ammeter(i assume you use an AC ammeter not a DC a DC ammeter cannot be used) ie you connected the resistor and ammeter in parallel with the transformer secondary ammeters must be connected in series only you were actually shorting the output of the transformer this may permanently damage the windings connect it in series with the load resistor like this one end of transformer secondary to one end of resistor, other end of resistor to one end of AC ammeter , other end of AC ammeter to other end of the transformer secondary your resistor wattage rating is less(about one fourth of what is required) you may still use it but make sure you dont connect it for more than a few seconds ( it will become very hot and may burn) you said your reading was fluctuating make sure to use an AC ammeter not a DC one if you dont have the AC ammeter but have an AC voltmeter , make the connections in parallel , using the AC voltmeter this will give voltage across resistor using ohms law VI*R calculate the current
Are you doing this all at AC? 60Hz? AC meter? With 2 ohms in the load (which is what I interpret you as doing, 2 - 1ohm resistors in series) and 30 volts that is 15 amps or 450 watts. But if you are reading only 3 amps, you are grossly overloading the transformer. And your resistors. Is the transformer rated for that much power? 450 watts? get some load resistors better suited to the rating of the transformer. Also, I note a lot of people mislabeling power supplies as transformers which they are not. .
Did you want to measure the amps across the transformer? Amperage depends on the load. You were in effect shorting out the transformer. NOT GOOD! You measure the current in line. It takes two measurements to read the amperage across the transformer and involves a calculation. I wonder now if the transformer is still working.
