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Re: Capacity Value Transformation



This looks like an attractive idea at first glance:

> Original Poster: "J. B. Weazle McCreath" <weazle-at-hurontel.on.ca> 
> 
> 
> Hello Coilers:
> 
> While reading a text on A.C. motors I came across an interesting circuit
> that might have application in Tesla coil power supplies.  The value of
> a capacitor can be increased by the use of a transformer, as in this
> example.  A transformer with a primary/secondary voltage ratio of 1:2
> has a 20 uF. capacitor connected across its secondary.  This causes an
> apparent capacity equal to the ratio squared times the capacitor value,
> in this case 80 uF., to be across the primary.
> 
> I'm wondering if by using a relatively low KVA rated 1:2 ratio transformer
> one could achieve power factor correction with relatively small values of
> PFC capacitors.  This would be particularly useful for larger coils that
> require capacitors in the hundreds of micro-farads for PFC.  The primary
> of the "capacitor transformer" would simply be paralleled with the MOT or
> pole pig primary.  One cap of 40 uF., a readily obtainable value in oil
> filled motor run caps, would yield an apparent capacity of 160 uF. in the
> power transformer primary circuit.
> 
> At present I do not have the facilities to check this idea out in actual
> practice, so I'd be interested in hearing from anyone who does try it.
> Thoughts, criticism, and other comments are of course welcome.
> 
> 
> 73, Weazle, VE3EAR/VE3WZL

The apparent tradeoff is using an extra component instead of more 
capacitance.  A second tradeoff is the need for a higher working 
voltage for the capacitor. Attention would have to be paid to the 
possibility of core saturation with the high circulating currents. Is 
such a tradeoff worth it?  

Regards,
malcolm