Hello the Group:
I accept the fact that a few rocks will be thrown, but allow me to describe
my source for a 5 Kw plate transformer. About in 1996 I started building
large Tesla Coils, in the 15 Kw input range. The ideal source for high
voltage power was a Pole transformer, run backwards. Over the years, I
obtained 4 in the 5-25 Kw range. These had a 14,400 VAC primary, with a
120/240 VAC secondary on the smaller ones, with a 22,600 VAC primary and a
120/240VAC secondary on the biggest one. The Tesla Coils worked well,
stopping traffic during each run at night, with 12-16 foot arcs !
OK, so I lost interest in my 61 KHz, 15 Kw Tesla coil work. Sold the main
system and still had 3 pole transformers. Amateur Radio called again, and
after getting active I decided to build a Linear. On the shelf were four
3-400Z tubes I got for free new in the box in 1969, so I designed an amp
around those tubes, which can be referenced as a low cost alternative.
Where to get a decent plate transformer became a real issue for me. The
shed had those two 5 Kw 14,400 to 240 VAC pole transformers, so I took a
closer look. Actually, they were both wound with two 7,200 VAC primary
windings and the standard 120/240 VAC output for residential use. A switch
allowed selecting primary series or parallel connections, at the
descrrestion of the power company who purchased the pole transformer. OK, I
paid $45 for these puppies, so I pulled it out of the can, let the oil
(NON-PCP) drain for a month and then started to modify this transformer.
The unit I had decided to work on was wound in a beautiful manner. With the
two 7,200 VAC windings on the outside, I simply cut off one layer at a time
from each winding. Sounds crazy, but it was extremely easy to do! I went
layer by layer, then would inject 10 VAC into the 240 VAC "Secondary" and
extrapolate the present AC output. I paralleled the two original 7,200 VAC
windings to provide the current I needed. I did check the wire size and
found I would easily be able to supply the required current, based on 500
CM/amp. Good enough for a 50% duty cycle.
The finished plate supply provided 2850 VDC under no load and 2700 VDC under
a 1300 watt output load, around 2,000 watts input. Ah, 168 mfd in the
filter cap. I used a boost/buck transformer in the circuit, the primary of
the boost/buck was fed by a autotransformer. So, it was easy to dial in the
planned for plate voltage. 1N5408 diodes and a step start allowed things to
stay alive.
If anyone wants pictures and further details, just ask. Pole transformers
are really low cost, if you have friend at the local electrical co-op!
This is NOT an approach for the beginner, consider this a marginal set of
details----Just some comments to consider---
Just another alternative,
Chuck W9POU
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