Needing to make a suitable current transformer
nzoomed, Sat Sept 05 2015, 10:21PMFor my DRSSTC, im using the UD 2.7C in my system.
I see these transformers here
But i know most people make them easily enough, but finding the suitable toroids is the hard issue, but i see in the link provided that they sell the same toroids that i believe loneoceans uses for his coils.
But i cant find these on mouser, is anyone aware of the part numbers to look for on mouser? As im planning to place my order for the UD components soon, and would like to get everything in one go.
Also, what is the purpose of the second current transformer? It doesnt look like many people are using two of them.
TIA
Re: Needing to make a suitable current transformer
Alex Yuan, Sun Sept 06 2015, 02:27AM
I've used these ferrite toroids with success, and they're only 81 cents each! Or 69.5 cents if you get 10 or more.
(DigiKey part number 495-3865-ND)
I've used these up to 900A.
Two current transformers are used for the current feedback and over current detection.
Alex Yuan, Sun Sept 06 2015, 02:27AM
I've used these ferrite toroids with success, and they're only 81 cents each! Or 69.5 cents if you get 10 or more.
(DigiKey part number 495-3865-ND)
I've used these up to 900A.
Two current transformers are used for the current feedback and over current detection.
Re: Needing to make a suitable current transformer
nzoomed, Sun Sept 06 2015, 03:26AM
OK, they look good, and mouser stock them too, do you use two of these per transformer in a figure 8 pattern?
I would like to know more about winding and assembling these as i cant find much info and i see so many different configurations, some people add another two smaller toroids to one large toroid, but if i can get away with using just these, it would be great.
And im unsure what wire people use, is solid core wire like from cat5 cable the best to use?
nzoomed, Sun Sept 06 2015, 03:26AM
OK, they look good, and mouser stock them too, do you use two of these per transformer in a figure 8 pattern?
I would like to know more about winding and assembling these as i cant find much info and i see so many different configurations, some people add another two smaller toroids to one large toroid, but if i can get away with using just these, it would be great.
And im unsure what wire people use, is solid core wire like from cat5 cable the best to use?
Re: Needing to make a suitable current transformer
Alex Yuan, Mon Sept 07 2015, 01:06AM
for <1000A you can just use two of them. Wind 32 turns on each of the toroids with any wire gauge around 22-24. It's not important what you wind it with, as long as it fits well. Ethernet cable works great. When you've wound both toroids with 32 turns, take one and loop it once through the other toroid, and that gives you a turns ratio of 1:32:32 which is 1:1024. Then just feed the wires from the second toroid to your driver.
Alex Yuan, Mon Sept 07 2015, 01:06AM
for <1000A you can just use two of them. Wind 32 turns on each of the toroids with any wire gauge around 22-24. It's not important what you wind it with, as long as it fits well. Ethernet cable works great. When you've wound both toroids with 32 turns, take one and loop it once through the other toroid, and that gives you a turns ratio of 1:32:32 which is 1:1024. Then just feed the wires from the second toroid to your driver.
Re: Needing to make a suitable current transformer
nzoomed, Mon Sept 07 2015, 10:20PM
I guess you have to solder the loop closed and keep the joint well insulated from touching the toroid.
Anyway its possible my coil will exceed 1000A, but i wont know until i have it running.
My main problem is now i may be expecting it to draw up to 20A from the mains!
nzoomed, Mon Sept 07 2015, 10:20PM
Alex Yuan wrote ...
for <1000A you can just use two of them. Wind 32 turns on each of the toroids with any wire gauge around 22-24. It's not important what you wind it with, as long as it fits well. Ethernet cable works great. When you've wound both toroids with 32 turns, take one and loop it once through the other toroid, and that gives you a turns ratio of 1:32:32 which is 1:1024. Then just feed the wires from the second toroid to your driver.
OK, that seems simple enough, i never realised they had two separate windings, i would have never thought that one turn around the second transformer would do anything!for <1000A you can just use two of them. Wind 32 turns on each of the toroids with any wire gauge around 22-24. It's not important what you wind it with, as long as it fits well. Ethernet cable works great. When you've wound both toroids with 32 turns, take one and loop it once through the other toroid, and that gives you a turns ratio of 1:32:32 which is 1:1024. Then just feed the wires from the second toroid to your driver.
I guess you have to solder the loop closed and keep the joint well insulated from touching the toroid.
Anyway its possible my coil will exceed 1000A, but i wont know until i have it running.
My main problem is now i may be expecting it to draw up to 20A from the mains!
Re: Needing to make a suitable current transformer
Alex Yuan, Tue Sept 08 2015, 01:00AM
yeah sorry for not clarifying, you loop it through once and solder it. I haven't had a problem with isolation, I just leave it open :P
My coils draw about 15A and I've been meaning to research a good PFC boost converter design to try out.
Alex Yuan, Tue Sept 08 2015, 01:00AM
yeah sorry for not clarifying, you loop it through once and solder it. I haven't had a problem with isolation, I just leave it open :P
My coils draw about 15A and I've been meaning to research a good PFC boost converter design to try out.
Re: Needing to make a suitable current transformer
nzoomed, Tue Sept 08 2015, 07:23AM
Thanks for your help.
I dont think my coil will exceed 1000A, but i could hit 800.
It will possibly draw 20A at the wall so i may need an electrician to wire up a 20A socket at the wall for this thing.
Getting excited, ive never built one of these before and im going for large!
nzoomed, Tue Sept 08 2015, 07:23AM
Thanks for your help.
I dont think my coil will exceed 1000A, but i could hit 800.
It will possibly draw 20A at the wall so i may need an electrician to wire up a 20A socket at the wall for this thing.
Getting excited, ive never built one of these before and im going for large!
Re: Needing to make a suitable current transformer
Alex Yuan, Tue Sept 08 2015, 03:40PM
in no way 1000A is a hard limit, just saying I'd use bigger current transformers in a larger coil
Alex Yuan, Tue Sept 08 2015, 03:40PM
in no way 1000A is a hard limit, just saying I'd use bigger current transformers in a larger coil
Re: Needing to make a suitable current transformer
nzoomed, Tue Sept 08 2015, 09:39PM
nzoomed, Tue Sept 08 2015, 09:39PM
Alex Yuan wrote ...
in no way 1000A is a hard limit, just saying I'd use bigger current transformers in a larger coil
OK, i also believe that the comparator chip for the OCD on the universal driver board has a limit of 8-9v, so with larger coils this could be an issue, although Loneoceans talks about adding another resistor to address this.in no way 1000A is a hard limit, just saying I'd use bigger current transformers in a larger coil
Re: Needing to make a suitable current transformer
Alex Yuan, Wed Sept 09 2015, 12:03AM
You pick your burden resistor to make sure it will be in that range.
Alex Yuan, Wed Sept 09 2015, 12:03AM
You pick your burden resistor to make sure it will be in that range.
Re: Needing to make a suitable current transformer
nzoomed, Wed Sept 09 2015, 02:13AM
Yes thats true, only problem is i wont know if the voltage from the CT will exceed that or not until i test it at full output, although i believe i should be OK if my coil stays below 1000A.
nzoomed, Wed Sept 09 2015, 02:13AM
Alex Yuan wrote ...
You pick your burden resistor to make sure it will be in that range.
You pick your burden resistor to make sure it will be in that range.
Yes thats true, only problem is i wont know if the voltage from the CT will exceed that or not until i test it at full output, although i believe i should be OK if my coil stays below 1000A.
Re: Needing to make a suitable current transformer
Alex Yuan, Wed Sept 09 2015, 02:05PM
you should be able to calculate your peak primary current, or at least have a very educated guess as to what you are aiming for.
Alex Yuan, Wed Sept 09 2015, 02:05PM
you should be able to calculate your peak primary current, or at least have a very educated guess as to what you are aiming for.
Re: Needing to make a suitable current transformer
nzoomed, Wed Sept 09 2015, 11:35PM
Yes, well ive been working on what wintesla is giving me and what others are getting with similar spec'd coils.
Im not 100% up with tesla coil theory so am using computer models.
nzoomed, Wed Sept 09 2015, 11:35PM
Alex Yuan wrote ...
you should be able to calculate your peak primary current, or at least have a very educated guess as to what you are aiming for.
you should be able to calculate your peak primary current, or at least have a very educated guess as to what you are aiming for.
Yes, well ive been working on what wintesla is giving me and what others are getting with similar spec'd coils.
Im not 100% up with tesla coil theory so am using computer models.
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