115V/400Hz transformer calculations

Feb 17, 2006 2 Replies

Would it be viable possibility for me to construct a 115V/400Hz isolation/step-down transformer for measurement purposes (i.e. hardly any power required)? I need only one and I have never done something like that before. It may be 1:1 or step-down to 3V.



Could someone please show me or point me to an example analysis/calculation to figure out what kind of core would be needed, how many windings and what the wire diameter(s) would be?



Any help would be greatly appreciated.



Thanks,



--DF


"Deefoo"

** Why on earth construct one ??

Standard AC power transformers work fine at 400 Hz if lightly loaded.

The now common toroidal type works to 10 kHz or beyond fully loaded.

Another candidate is a small audio output tranny from a valve amp.

........ Phil

analysis/calculation

what

You can use (just about) any 60 Hz transformer on 400 Hz. The 120 VAC primary would not saturate until about 800 volts. You could also use an audio transformer, especially one designed for tube circuits. If you have an old power transformer core, you can probably use a rough figure of 0.05 volt per turn at 60 Hz, and 0.4 volts/turn at 400 Hz, for about a 50 W (60Hz) transformer. You can try wrapping an approximate number of turns, and then slowly apply voltage until the current starts to increase sharply (this is saturation). Then just add turns as needed. You can figure wire size from a chart, but for measurement purposes, almost any fine magnet wire that will fit the core should be OK. #36 is easy to work with and should handle 100 mA or so.

Paul E. Schoen

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