[Amps] Control transformers

[TexasRF at aol.com]

Jeff, I have not done that but conceptually it should work well. If you use 
 two of the 3kva transformers, one would expect to generate enough d.c. to 
supply  a 6 KW load.
 
The voltage doubler will charge the filter C to 2.8 times the rms voltage  
so two of the 600v units would have a no load voltage of 3394v and full load 
 maybe 3100v or so.At 6 KW, the current could be upwards of 1.7 amps.
 
There are other considerations such as the much higher peak currents caused 
 by a C only filter that would tend to reduce the current capability 
somewhat to  prevent over heating the transformers. Fortunately the copper losses 
are related  to current squared so a modest reduction in current equates to 
a large reduction  in heating.
 
You would wise to find a way to test the insulation break down between  
windings and the core. Perhaps you could build or borrow a break down tester.  
They are very easy to build based on an old microwave oven transformer.
 
For a very rough test, you could connect a 100w incandescent light bulb in  
series with the 120 or 240v primary and connect the 600v windings in 
series. One  end of the 1200v can be connected to the core and that would subject 
the other  end of the 1200v winding to about 1700v peak. If the 120v 
windings were  connected in parallel and 240v applied, the secondary voltage would 
then be  about 3400v peak. You can't run it this way but fine for a brief 
test. The light  bulb will limit the current flow in case there is a 
breakdown. It will also give  a relative indication of the amount of leakage in the 
transformer. One would  expect only a dim glow if all is well. Also, it would 
be a good idea to connect  the two transformer cores together and to ground 
(or neutral) for the brief  test. Be careful as bad stuff can happen!
 
73,
Gerald K5GW
 
 
 
 
In a message dated 4/8/2016 11:16:07 P.M. Central Daylight Time,  
amps at contesting.com writes:

Good day,
I have learned alot from  this list over the years. What I propose to try 
may work or it wont. Im  thinking it wont work but it dont hurt to ask. From 
time to time I come across  1kva,2kva,3kva control transformers. 0 -120v on 
one side and 0  -240,480,575,600 volts on the other. If I was to series two 
of the 600 volt  windings then feed a fullwave doubler, would this work or 
not? I would also  like to series the 120v side feed it 240v. For there 
intended purpose I think  with control transformers, the higher voltage winding 
serves as the primary  and the secondary is the 120v winding. Not sure how 
robust machine control  transformers are.or if there is enough insulation 
between primary and  secondary. Im sure current capacity would drop if I step up 
the  voltage.

Jeff

KD4LYH
_______________________________________________
Amps  mailing  list
Amps at contesting.com
http://lists.contesting.com/mailman/listinfo/amps