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Author Topic: Voltage Transformer  (Read 3582 times)
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W9LCE
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« on: February 15, 2015, 02:34:25 PM »

What does it take - to build my own Toroid Power Transformer?
(I've never tried to wind a toroid - maybe this is stupid!)

Emergency Preparedness can include solid state (even EMP they are saying - with a necessary Faraday Cage - a metal garbage pail)

- I bought a couple dynamotors - but they are SO Noisy
[a new one from Fair Radio is:  IN: 5.5v@31A or 170.5w  and OUT: 600v@175ma or 105w - - that is 61.6% efficiency - not too bad - actually for 6v in - I would get about 650v out - or 114.5w)
[I have a 6v filament transformer (34A - 204w) - then I would run the existing 120vAC Power Supply - but 66% (fil tr) of 66% (PS) is only 43% efficiency - 87w - a single 807]

so - considering -
to run my gear from 6V deep discharge batteries - how about converting it up to 600v - by solid state - to run my Transmitter.  (AND - I could even turn THIS off - for reception - when not transmitting!)

I recently saw a schematic for a 2 transistor flip-flop to substitute for a vibrator (so - just to substitute for the dynamotors -)

for near 120 watts (pr 6146s) - I need a GOOD Transformer:  6v to 600v at 120w  would be 20A at 6v.   But transformers run about 66% efficiency - so I probably will actually need about 30A. 

To build my own 6v to 120v transformer (I've seen the use of a toroid PS)  I would need #8 wire (?#9) to carry a total of 30A at 6v.  Using stranded would be much easier - possible? - reasonable?

[Somewhere I read about the use of a "cut" toroid - where it is two half circles that somehow can be fastened back together - wind primary one side/secondary the same or the other - and reform the full toroid.  Is there such?]

to convert to 120v - I need a 20:1 winding ratio.  So - How many turns would be required for 6v to make a decent transformer? (- 120v would add 20 times that many turns - probably using #30 wire)  How large a toroid should I get?  Are any such available prewound - at a reasonable cost?  where?  for 30A at 6v what switching transistor (pair) would be recommended? 

(the schemat was to substitute for a vibrator, and showed a pair of 2n3055s - I figure on doing this to my Heath GP-11 and to a couple vibrator CB rigs converted to 10M - that I have for backup -  4w)  The mechanical Vibrators do not have a long life!  (in case it becomes an extended disaster!)

I've lived at/through 3 tornadoes (MO and IN) and 3 hurricanes (Southern ALA and FL) - I'm concerned about disasters.
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Patrick J. / KD5OEI
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« Reply #1 on: February 16, 2015, 01:49:32 AM »

This topic might help.
http://amfone.net/Amforum/index.php?topic=36139.0
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Radio Candelstein - Flagship Station of the NRK Radio Network.
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« Reply #2 on: February 18, 2015, 07:54:35 PM »

(the schemat was to substitute for a vibrator, and showed a pair of 2n3055s - I figure on doing this to my Heath GP-11 and to a couple vibrator CB rigs converted to 10M - that I have for backup -  4w)  The mechanical Vibrators do not have a long life!  (in case it becomes an extended disaster!)

Solid state is definitely the way to go but 2n3055s are pretty old technology and beside a pair wont come near handling the current you are quoting.  Modern high current switching FETs are a way better choice.

Are you locked into 6 volts?  12 volts would be much better and 24v better yet.  The design would be relatively simple. A pair or 4 high current FETs like IRFZ46 or similar driven push pull with a TC4428 driven by a CD4060 square wave oscillator at about 50 khz or so.  The transformer would be a relatively small 2.5 inch powdered iron core followed by a fast (FRED) bridge rectifier and filter cap.  Efficiency would be in the mid 95% range. If you decide to go this way I could draw you up a schematic
73s  VE3ELQ
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Patrick J. / KD5OEI
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« Reply #3 on: February 19, 2015, 12:17:39 AM »

Vibrators run at various frequencies, 50, 60, 100 Hz, maybe others.

Within reason I've found that as the frequency is increased the voltage that can be put across the LV winding increases. In this way I was able to make a nice 400Hz 130W inverter using a 6.3VCT 20A transformer.

The output voltage is regulated to within a few volts by a feedback circuit and rectifier that turns on transistors to reduce drive to the oscillator-driven push pull drive amp. A toroid might have done better than the EI core transformer used, but toroid power transformers were not very common or cheap at all back then.

Just something as an idea for when you make this power supply, that it is possible to get good regulation one way or another if you design it for more volts than required.
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Radio Candelstein - Flagship Station of the NRK Radio Network.
W9LCE
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« Reply #4 on: February 19, 2015, 08:56:39 AM »

You ran a 60hz transformer at 400 hz? (like - WWII stuff)  from 6.3v to 120v - what kind of efficiency did you get?  what was the actual output - voltage and current?

6.3v at 20A is 126w - 100% efficiency would have been 125v at 1A!
normal 66% efficiency would give an output of 125v at some 660ma -

and yes - while I have not bought the batteries yet - I have several dynamotors at 6v input (output 600v at 185ma - just right for my 807s and 6146s) (from their ratings - I figured them out as near 60% efficiency) - so I am considering several (2-3) larger 6v batteries - with a solar panel for 6v. (When I can afford it!) 

(and I'm starting to study internet sources about switching power supplies) 

(and also following the presentations on your "Silicon Carbide FETs" - this may be the better way to go - PWM/Class E et al - I was aware of them -but  hadn't been trying to keep up on all this stuff - "don't know nothin"!)

but the big question - I asked - about how many turns should the primary winding on the toroid transformer be?  What kind of stats do you look at to determine it?
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