Hi,
I got a spare toroidal transformer, input: 230v, output: 48v, 100va. My little project is a 24v DC preamp, so I can use this spare transformer as the power transformer for 115v input, right?
A friend of mine advise me not, because the max output power is now 25va instead of 100va, is it right?
I got a spare toroidal transformer, input: 230v, output: 48v, 100va. My little project is a 24v DC preamp, so I can use this spare transformer as the power transformer for 115v input, right?
A friend of mine advise me not, because the max output power is now 25va instead of 100va, is it right?
Hi . If input voltage twice lower than designed ,output voltage will be twice lower too . But there is one bonus - such trafo will have very low consumption from mains when no load or with little load. I think power will reduce twice also , if its rated for 48v 2amp , you still can draw 2 amp from it ,you just get lower voltage 24v from it .
Ximikas must be close to the truth.
The power limit of a transformer is often decided by the maximum temperature at continuous operation. The temperature is mainly decided by the current and the winding resistance (primary+secondary). When the current is the same but the voltage half, you first order have half the power. But, a transformer has an output voltage drop due to winding resistance. And, as the winding resistance is unchanged the voltage drop is relatively more important with 115Vac input than with 230Vac input such that the voltage at full loading becomes a little less than half.
There is no risk using the transformer like that but the core could do (much) better with optimized windings.
The power limit of a transformer is often decided by the maximum temperature at continuous operation. The temperature is mainly decided by the current and the winding resistance (primary+secondary). When the current is the same but the voltage half, you first order have half the power. But, a transformer has an output voltage drop due to winding resistance. And, as the winding resistance is unchanged the voltage drop is relatively more important with 115Vac input than with 230Vac input such that the voltage at full loading becomes a little less than half.
There is no risk using the transformer like that but the core could do (much) better with optimized windings.
Both the responses above are correct
The primary and secondary current capacity remains the same, but the secondary voltage is proportional to the reduction of input voltage.
So -
Voltage transformation 230/115 * 48 = about 24Vac output, at the same (100VA/48v) = 2A ac nominal output current.
You can expect 48VA output. Should be far more than enough for a preamplifier!
The transformer will run mechanically-quiet, and cool, because the core is sized for a much higher applied primary voltage. As Fauxfrench point - effectively the core is now over-sized for the application - but that is not a disadvantage, for a preamp this should work very nicely.
The primary and secondary current capacity remains the same, but the secondary voltage is proportional to the reduction of input voltage.
So -
Voltage transformation 230/115 * 48 = about 24Vac output, at the same (100VA/48v) = 2A ac nominal output current.
You can expect 48VA output. Should be far more than enough for a preamplifier!
The transformer will run mechanically-quiet, and cool, because the core is sized for a much higher applied primary voltage. As Fauxfrench point - effectively the core is now over-sized for the application - but that is not a disadvantage, for a preamp this should work very nicely.
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