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Registered Member #3926
Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525
Hello everybody after two attempts to make a suitable bobbin to slot over my UK bought 60x55x15 U cores (129x55x15 O/A) I have now had some success, The bobbin was machined by a work collegue from ABS plastic, after using black nylon I discovered this wasnt a suitable insulator. Dimensions are;
Outer diamater 57mm (to suitably sit inside the core away with decent spacing from the primary)
Inner diameter is 21.5mm (as the core is 15 horizontal length would calculate to 21.2132034) I would show the calculation but have never done calculations on HTML
Wall thickness increased to 5mm
Outer minor diamater is 31.5mm
Height is 78mm to sit inside the core
3mm radial slots of 12.5mm depth, around 5-6mm of this depth is used by the windings.
Secondary turns was a complete guess maybe 400-600
Using a safe 12 primary turns I'm getting quite some output, maybe 10Kv at 100ma, I have not tested output or input powers as of yet, will do by later this evening.
At 250khz voltage is estimated around 45Kv, it can jump around 15mm. When at 35khz voltage can jump 5-6mm, according to air breakdown voltage this would be about 15-18kv
This transformer is running from a fullbridge which powers a ferrite toridial core, using rectified mains, I have wound 11 turns for 200volts (under highest tested load so far) into the homemade transformer which uses 12 turns.
I just have one question, I need to calculate a tesla coil MMC, using all the internet calculators I have come to conclusion that they will not work for a HF transformer, any advice?
I have also finished winding the tesla coil (by hand...) using PVC drain pipe 110OD, 1150 turns as 20-80 unraveled before lacquer.
Sorry for the video, it is a little out of proportion, The green box is about 200mm X 140mm x 60mm
Registered Member #3926
Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525
Sorry for the double post but I have tried numerous times to edit my original post. Is there any good websites where I can upload a video of the transformer working to show everybody?
Registered Member #3926
Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525
Well I measured input today and input power is approaching 1.5kw, I hope this results in an impressive SGTC, I now need to calculate an MMC but cannot find a calculator that I can use with high frequency transformers, only 50/60hz.
Registered Member #46164
Joined: Wed May 07 2014, 08:16AM
Location: California, USA
Posts: 89
Platinum wrote ...
Sorry for the double post but I have tried numerous times to edit my original post. Is there any good websites where I can upload a video of the transformer working to show everybody?
Registered Member #1875
Joined: Sun Dec 21 2008, 06:36PM
Location:
Posts: 635
At these driving frequencies you're going to have to rectify the output of your transformer to use with a large spark gap coil. Put avalanche-rated diodes like these in series:
Once your output is DC, you can use whatever capacitor you want, so long as it resonates with your primary at the correct frequency for your secondary. It's hard to say what would be ideal for your system without knowing more details about your system.
You'll need to make sure there's enough leakage inductance (or a high enough drive frequency) in your transformer to handle the capacitor charging.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
thats pretty good, many ignition coils and flybacks burnout when they try that for to long. but when we make our own we can kinda make the secondary more ideal for what we do.
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My finished homewound/made ferrite HF HVAC transformer
