# 115V/400Hz transformer calculations

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#### Deefoo

Jan 1, 1970
0
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

P

#### Phil Allison

Jan 1, 1970
0
"Deefoo"
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?

** 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

P

#### Paul E. Schoen

Jan 1, 1970
0
Deefoo said:
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
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
www.pstech-inc.com

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