Hi,
I'm looking to design an HT power supply for a YC156 (3CPX5000A7)
triode. One approach is the common single phase input, single phase
transformer, lots of expensive high voltage capacitors.
I've been considering another approach, which seems to me to be much
simpler:- use a 3-phase supply, 3-phase transformer, and a bridge with 6
diodes. This gives 4.2% RMS ripple, without any storage capacitors,
compared with a totally unacceptable 48.2% for single phase bridge
without any storage capacitor or choke.
I suspect the 3-phase transformer will cost more than a single phase
one, as there are more windings, but this cost is probably more than
offset by the cost savings in not having any electrolytic capacitors.
The other potential advantage, is that in the event of an arc in the
tube, there is far less stored enegy, so protection systems don't need
to be as rugged. Assuming you have a 3 phase supply (which I do) it
seems the obvious way to go.
However, somone once told me that such a system with no storage
capacitance would destroy a transformer. Does anyone know if this is
true ? What approaches are taken on large HT supplies for amplifers much
bigger than amatuer ones? 3-phase would obviously be used, but do they
use storage capacitors ??? Perhaps just a small amount would be enough,
but I'm not sure why any would be needed.
I once played around with the concept of using three single phase
transformers on a 3-phase supply. This works fine, which does mean it
would be possible to design an HT supply that worked with a 3-phase
supply, or used the three tranformers in parallel to use it from a
single phase supply. It would only take an hour or so to reconfigure the
transformers to swap from single phase to 3-phase operation.
Comments ??
--
Dr. David Kirkby Ph.D,
email: drkirkby@ntlwold.com (formally davek@medphys.ucl.ac.uk)
web page: http://www.david-kirkby.co.uk
Amateur radio callsign: G8WRB
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