[Boatanchors] High Voltage 400 Hz Supply

[Jim Wiley]

Instead of an inverter, how about an audio oscillator followed by a 
small amplifier, into a reversed output transformer?   A Wein bridge or 
phase-shift oscillator would produce a reasonably pure sine wave 
(important for properly calibrating an AC voltmeter).. The frequency 
could be made adjustable if desired. 


Inverters tend to produce non-sinusoidal waveforms that can complicate 
the calibration process.


However, to even more simplify the situation, an ordinary AF signal 
generator could be used as the source, followed by a utility amplifier 
(and old stereo amp would be just fine) and again, a reversed audio 
output transformer (could be a reversed "70 volt" PA system speaker 
transformer).


The only remaining problem is to determine exactly how much AC voltage 
is being generated.  If your scope is properly calibrated (lots of ways 
to do that) then all you need is to generate the signal,. measure it 
with the scope, and do a little arithmetic to come up with the AC RMS 
voltage.


The entire setup could be assembled and taken down as  needed for 
occasional use.


- Jim, KL7CC

 

David C. Hallam wrote:
> I am considering various ways to build a HV 400 Hz supply to calibrate 
> AC VTVM's.  Current requirement is obviously low and I need variable 
> voltage up to 300VAC,  So what I need is some type of an inverter to 
> convert from 60 Hz to 400 Hz and a transformer to step up to 300V.  As I 
> see it, the inverter needs to have a voltage variable output, or can 
> accept a variable line input from a 120V 60Hz variac, or I need a 400 Hz 
> variac to put on the output.
>
> Since this will have very limited usage, cost is important.  Any 
> suggestions on how to do this at low cost?
>
> David
> KW4DH
>
>