CV Transformer - Capacitor on separate winding ?

[Dave Dunfield]

>>Disconnecting this capacitor "cures" the excess current draw and
>>the chassis voltages come up fine (still running through variac at
>>reduced AC voltage with series light bulb as I expect this cap is
>>part of a "line voltage regulator".
>>
>>The transformer is labled "C.V." (Constant Voltage?)
>
>The cap needs to be there.  An unloaded CVT runs hot and draws 
>more current due to the highly reactive load.  A side effect
>of storing power in a resonant circuit (floating coil and cap).
>As the transformer is loaded the current remains the same but
>more stored energy is transfered to the active load.  I have
>a Compupro Chassis, TEI and even a spare supply of that style.
>I also have 120V/120V CVT for systems that do not have one 
>internally.  They tend to run warm under normal cases.  It 
>should with a modest load (auto headlamps are handy for this)
>behave and also not blow primary side fuse(s).
>
>By current switchmode tech they are scary but represent old 
>magamp thinking and are reliable devices.

Thanks - yes, I figured the cap needs to be there, but removing
it during low power tests identified it as the cause of the high
current draw - I guess I was not clear on this as several people
have emailed me to warn me not to run it without the cap.

But I think you have provided the information I needed - normally
I bring up a chassis with no load, initially at very low line voltage
to allow the big electrolitic filter capacitors to take it easy as
they reform.... But I've not encountered a resonant transformer
design before - if I understand you correctly, not having any load
at all is putting the transformer/cap into a state where it is drawing
excessive power - I will try supplying a load. Do I need to load all
of the windings, or will drawing from just the 8V supply be adaquate
(I would expect the latter).

Thanks,
Dave
-- 
dave04a (at)    Dave Dunfield
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