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Re: [TCML] Homebuilt Transformer - Can you add shunts?
Hi Phil,
Phil Tuck wrote:
However it may all be immaterial .......
Quoting from one reply in the thread at
http://4hv.org/e107_plugins/forum/forum_viewtopic.php?28717 at 4HV.org "If
at all possible you should not introduce an air gap into the magnetic
circuit it will (dramatically) increase the current that the transformer
draws with no load connected and it will give poorer regulation (change in
output voltage vs. output current."
Yes, regulation will certainly become less than what it could be without
a gap.
Doing some basic tests today with wire around the core and shimming it
apart
confirms this. The shunts in an NST aren't an actual air gap as I
understand
it, having never de-potted one.
No, not at all. There is no air gap in an NST. NST's use shunts. For the
higher voltage NST's, there are usually 2 secondary windings.
Arrangement varies. An example is a Franceformer 12/60. The primary is
center between the two E cores. A secondary coil is place on each side
of the primary. Shunts are inserted between the primary and secondary
coils top and bottom from center core (4 positions in all).
Maybe some ascii art (fixed width font).
|------------------------||------------------------|
| || |
| |-------------------||-------------------| |
| | |||| ||||<---------------- SHUNTS
| | |-----| |||| |----------| |||| |-----| | |
| | | | |||| | | |||| | | | |
| |-| |------| |------| |-| |
| | | | | | | |
| | | | | | | |
| | SEC | | PRI | | SEC | |<--------E-CORE
| | | | | | | |
| |-| |------| |------| |-| |
| | | | |||| | | |||| | | | |
| | |-----| |||| |----------| |||| |-----| | |
| | |||| ||||<---------------- SHUNTS
| |-------------------||-------------------| |
| || |
|------------------------||------------------------|
I have tried some tests today and using the currently unused outside legs
for a new secondary gives me 0.95 volts per turn, but winding a secondary
around the core again as the original was, gives 1.76 volts per turn.
Putting a secondary on an outside leg means there is also an issue
regarding
" leakage flux would be excessive, and the transformer would have poor
regulation".
Yes, but this was current limited transformers do. The leakage is part
of the design as is the poor regulation.
http://www.franceformer.com/
Go down the "Technical" section on the left side of the page and click
on Frequency Asked Questions. Then look at item #2 "How Neon Sign
Transformers are different than power transformers".
Take care,
Bart
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