Nearly there with IBM 029 KeyPunch

Tony Duell ard at
Fri Jun 12 13:52:46 CDT 2009

> The other thing that changes with f is the inductive impedance of all the
> (other) windings of the transformer. Ferro-resonance transformers do not rely
> only on the resonance principle, magnetic/inductive issues are also very
> involved. I'm not at all convinced that simply changing the C is adapting the
> supply for the new frequency (50 Hz). That you are having to go so far off the
> theoretical new C would tend to support this.

Possibly. However, I have a ferroresonant supply (for a pair of Diablo 
Model 30 hard disks) which has tappings on the 'resonant' winding for 50 
or 60 Hz operation. There's a table inside saying how to strap it for 
different input voltages and t h2 frequencies. The capacitor, IIRC is not 
changed, just the tappings.

This would seem to indicate it's possible to design a ferroresonant 
transformer with the 'main' windings are OK for either frequency. Of 
course this doesn't mean all such transformers are designed that way. 

And as others have pointed out, changing the value of the capacitor is 
not quite the same thing ans changing the tappiongs on the inductor.


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