Re: Typical bandwidth of 60hz wallwart transformers


"Barry Lennox" <bt.l.barryl@xxxxxxxxxxxxxxx> wrote in message
news:hsjn235s2m6cotuh1pqn697t2tt05bs2ms@xxxxxxxxxx
On Sun, 22 Apr 2007 10:36:13 -0400, Jim Flanagan
<jflan@xxxxxxxxxxxxxxx> wrote:

Hi -
I am going to be designing a 400hz 3ph test generator
(about 1W max) and want to use some 60Hz transformers
to use in a DC-AC inverter (linear). Would these
show a significant rolloff at 400Hz or is the bandwidth
OK for this application? What about using some small
audio transformers? I need the output to be around 160 Vrms
and am not sure if a miniature audio transformer has sufficient
dielectric properties to handle this. Obviously, I am trying
to do this on the 'cheap'. Any suggestions?

No problem, I have used el-cheapo transformers (designed for 50 Hz)
several times at 400 Hz (for aircraft test sets) and variable from
about 100Hz to 3-4 Khz. They work fine, even though I'm sure the
efficiency drops off. At the other end of the scale, they also work
OK down to 16 Hz, again I'm sure the efficiency drops off
dramatically, but for the power I required (and your 1 Watt) it did
not matter.

Barry

I don't see any problem. I once measured the frequency response of a
standard laminated core 12 V filament transformer, and the minimum loss was
actually somewhere between 300 and 400 Hz. Also used the 12v center tapped
secondary of a Radio Shack transformer as a 16 to 4 Ohm autotransformer for
audio. It was quite usable, but sounded a bit mellow.

Tam


.

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