[Milsurplus] [MMRCG] Parts Box Inverter

Robert Nickels ranickels at gmail.com
Tue Apr 2 13:39:39 EDT 2024


On 4/2/2024 10:11 AM, Ray Fantini wrote:
> The transformer is a 36 volt and although it is not happy about being 
> driven by a square wave it works and provided a good range of output. 
> Thru trial and error found this one to be best. Transformers work both 
> ways so you can use the primary as the secondary and they don’t know 
> the difference. The trick is to not exceed the insulation value.  
> Cheap Radio Shack transformers tended to get hot or buzz.

Good job Ray!

The transformer is the secret to these things, and many just won't work 
efficiently (hot) or put enough back EMF into the FETs that they get hot 
or fail from overvoltage. Mallory built bazillions of mechanical 
vibrators and vibrapacks and literally wrote the book on how to design 
power supplies using them - you can find it online: 
http://www.tubebooks.org/books/mallory_vibe.pdf

There's a whole chapter on transformer design (and more) - but of course 
you can't buy one nowadays.  However you can scrounge them - or 
experiment with what you have and maybe find one that has the desired 
magnetic characteristics. Vibrators typically ran around 100 - 120 
Hz.    I haven't tried a 400 Hz transformer yet but it might be a good 
way to go, and a bit smaler and lighter as well.

73, Bob W9RAN
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