Author Topic: My first QCW  (Read 2638 times)

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2987
  • Karma: +140/-2
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: My first QCW
« Reply #20 on: October 14, 2024, 01:14:27 AM »
Quote
The toroid heated up so much that it collapsed by a few millimeters (toroid is 3d printed).
Is there space between top of secondary winding and toroid?  If little or no space, induction heating of toroid is likely cause of heating (and of wasted power).  Magnetic field lines need a path to return to bottom.  (I've built a couple coils with ferrite plates between secondary top and toroid to minimize gap needed.  Much easier and lighter to leave a gap.  I'd recommend a gap of roughly secondary radius, half radius at very minimum.

Other less-likely possibility is poor electrical connection between foil tape and secondary top.  Most foil tape has non-conductive (or minimally conductive) adhesive.  Usually there are enough random points of contact at edges.  Sometimes requires folding under a narrow hem on tape edges to contact adjacent foil.
David Knierim

Offline Mathieu thm

  • High Voltage Technician
  • ***
  • Posts: 106
  • Karma: +8/-0
    • View Profile
Re: My first QCW
« Reply #21 on: October 14, 2024, 08:50:34 PM »
Quote
Is there space between top of secondary winding and toroid?  If little or no space, induction heating of toroid is likely cause of heating (and of wasted power).  Magnetic field lines need a path to return to bottom.  (I've built a couple coils with ferrite plates between secondary top and toroid to minimize gap needed.  Much easier and lighter to leave a gap.  I'd recommend a gap of roughly secondary radius, half radius at very minimum.
Yes, there is a gap between the secondary and the topload, the size of the gap is about the size of the secondary radius.

Quote
Other less-likely possibility is poor electrical connection between foil tape and secondary top.  Most foil tape has non-conductive (or minimally conductive) adhesive.  Usually there are enough random points of contact at edges.  Sometimes requires folding under a narrow hem on tape edges to contact adjacent foil.
I'll look into it to improve the contact.
I've also thought of a hypothesis: I've noticed that the 2.5 mm² copper that serves as my breakout point has changed color because it's very hot, and on the video, you can see that after a burst, the tip is red. So maybe this heat is also dissipating into the topload, which is enough to make it heat up.
As can be seen on this screenshot :

Offline Benjamin Lockhart

  • High Voltage Technician
  • ***
  • Posts: 141
  • Karma: +15/-0
    • View Profile
Re: My first QCW
« Reply #22 on: October 14, 2024, 10:44:23 PM »
My guess is simply induction heating from the primary and secondary current. Like Dave said, I'd raise the toroid a little bit.
Another thing that might help would be cutting a thin strip of foil out of the toroid so it doesn't act as a shorted turn.
« Last Edit: October 14, 2024, 10:47:52 PM by Benjamin Lockhart »

Offline Mathieu thm

  • High Voltage Technician
  • ***
  • Posts: 106
  • Karma: +8/-0
    • View Profile
Re: My first QCW
« Reply #23 on: October 14, 2024, 11:55:58 PM »
Quote
My guess is simply induction heating from the primary and secondary current. Like Dave said, I'd raise the toroid a little bit.
Another thing that might help would be cutting a thin strip of foil out of the toroid so it doesn't act as a shorted turn.

I'll try it next time

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2987
  • Karma: +140/-2
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: My first QCW
« Reply #24 on: October 15, 2024, 04:39:15 AM »
Quote
I've also thought of a hypothesis: I've noticed that the 2.5 mm² copper that serves as my breakout point has changed color because it's very hot, and on the video, you can see that after a burst, the tip is red. So maybe this heat is also dissipating into the topload, which is enough to make it heat up.
My QCW copper breakout point tip also melts a bit when initially sharp.  I doubt that heat conducts enough from copper breakout to topload.  It is only momentarily that hot.
David Knierim

Offline Anders Mikkelsen

  • Global Moderator
  • High Voltage Technician
  • *****
  • Posts: 133
  • Karma: +20/-0
    • View Profile
Re: My first QCW
« Reply #25 on: October 15, 2024, 01:45:59 PM »
Excellent performance! Glad to see you worked out the issues in the end. Toroid heating is very likely from induction heating by the fields around the coils as mentioned. Steve Ward mentioned that he had to slot his toroid for this reason, to avoid the shorted turn effect. This would have the added effect of not blocking the primary field near the breakout point, which might affect the degree of corkscrewing in the arcs and possibly the spark growth. It's also possible to use thicker metal for the toroid, to give less heating for a given induced current, but the benefit here will be limited by the skin depth of conduction at the operating frequency.

Offline Mathieu thm

  • High Voltage Technician
  • ***
  • Posts: 106
  • Karma: +8/-0
    • View Profile
Re: My first QCW
« Reply #26 on: October 15, 2024, 07:17:25 PM »
Quote
Excellent performance!

Thanks !

Quote
My QCW copper breakout point tip also melts a bit when initially sharp.  I doubt that heat conducts enough from copper breakout to topload.  It is only momentarily that hot.
Quote
Toroid heating is very likely from induction heating by the fields around the coils as mentioned. Steve Ward mentioned that he had to slot his toroid for this reason, to avoid the shorted turn effect. This would have the added effect of not blocking the primary field near the breakout point, which might affect the degree of corkscrewing in the arcs and possibly the spark growth. It's also possible to use thicker metal for the toroid, to give less heating for a given induced current, but the benefit here will be limited by the skin depth of conduction at the operating frequency.

I will make the changes on the toroid, starting by increasing the gap between the secondary and the toroid. And if it's not going to change much, I'll be looking to slot the toroid.

Offline Mathieu thm

  • High Voltage Technician
  • ***
  • Posts: 106
  • Karma: +8/-0
    • View Profile
Re: My first QCW
« Reply #27 on: October 25, 2024, 07:46:41 PM »
I increased the height of the toroid, all went well, and a few tens of seconds later I couldn't pass more than about 80cm of arc without triggering the ocd. so I put the toroid back on as before but the same problem occurs.
I thought it might be the mmc that had lost some of its capacity as I've been abusing it, but it has exactly the same capacity as when I started (12nF).

is it possible that the mmc loses some of its capacity after a few seconds of operation and then returns to its normal capacity?
Any suggestions?

EDIT : I tested the primary with a dummy load, and everything worked normally, maybe a problem with the secondary , but I don't see where it could be.
« Last Edit: October 25, 2024, 10:07:36 PM by Mathieu thm »

Offline Mathieu thm

  • High Voltage Technician
  • ***
  • Posts: 106
  • Karma: +8/-0
    • View Profile
Re: My first QCW
« Reply #28 on: October 26, 2024, 07:49:37 PM »
Good news !
The qcw works as before, I was afraid there might be a problem with the electronics, but no. The problem was that part of the arc was inside the secondary, creating a small carbon track.



I replaced the wooden support and improved the insulation at the level of the threaded rod.
No more toroid heating problems with this gap between toroid and secondary :



« Last Edit: November 04, 2024, 11:10:04 PM by Mathieu thm »

Offline Benjamin Lockhart

  • High Voltage Technician
  • ***
  • Posts: 141
  • Karma: +15/-0
    • View Profile
Re: My first QCW
« Reply #29 on: October 27, 2024, 06:24:25 AM »
Looks great! I hope to build a QCW someday.

High Voltage Forum

Re: My first QCW
« Reply #29 on: October 27, 2024, 06:24:25 AM »

 


* Recent Topics and Posts

post Re: My DRSSTC1 rebuild / Strange GDT ringing
[Dual Resonant Solid State Tesla coils (DRSSTC)]
LoFoTroFo
Today at 06:17:25 PM
post Re: Single board for SSTC and DRSSTC operation
[Solid State Tesla Coils (SSTC)]
davekni
December 01, 2024, 10:45:49 PM
post Re: My DRSSTC1 rebuild / Strange GDT ringing
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
December 01, 2024, 09:53:13 PM
post Re: My DRSSTC1 rebuild / Strange GDT ringing
[Dual Resonant Solid State Tesla coils (DRSSTC)]
LoFoTroFo
December 01, 2024, 03:42:44 PM
post Re: Last cap in CW always blowing up
[Voltage Multipliers]
JoeBusic
December 01, 2024, 03:30:50 PM
post Scientific Atlanta (Cisco) 1 GHz Combiner and PSU Teardown
[Electronic Circuits]
Mads Barnkob
December 01, 2024, 11:43:09 AM
post GU-81M Hartley Driven VTTC
[Vacuum Tube Tesla Coils (VTTC)]
janno288
December 01, 2024, 10:46:59 AM
post Single board for SSTC and DRSSTC operation
[Solid State Tesla Coils (SSTC)]
Simranjit
November 30, 2024, 09:10:38 PM
post Re: My DRSSTC1 rebuild / Strange GDT ringing
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
November 30, 2024, 07:29:22 PM
post My DRSSTC1 rebuild / Strange GDT ringing
[Dual Resonant Solid State Tesla coils (DRSSTC)]
LoFoTroFo
November 30, 2024, 01:47:58 PM
post Re: Many Multiple Mini Capacitor
[Dual Resonant Solid State Tesla coils (DRSSTC)]
rikkitikkitavi
November 29, 2024, 02:10:44 PM
post Re: Many Multiple Mini Capacitor
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
November 28, 2024, 09:34:29 PM
post Many Multiple Mini Capacitor
[Dual Resonant Solid State Tesla coils (DRSSTC)]
rikkitikkitavi
November 28, 2024, 07:52:42 PM
post Re: Oscilloscope recommendation for SSTC?
[Solid State Tesla Coils (SSTC)]
Simranjit
November 26, 2024, 11:34:05 PM
post Re: The evolution of a solid state Tesla coil
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Anders Mikkelsen
November 25, 2024, 01:03:46 AM
post GU-81M VTTC 2.7MHz Help
[Vacuum Tube Tesla Coils (VTTC)]
janno288
November 24, 2024, 01:53:22 PM
post Re: My SSTC's IGBT's blow up when toroid is added
[Solid State Tesla Coils (SSTC)]
AstRii
November 21, 2024, 07:17:16 PM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic Circuits]
petespaco
November 20, 2024, 12:11:18 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic Circuits]
betalab99
November 19, 2024, 05:41:27 PM
post Re: Testing and teardown of a commercial induction heater
[Electronic Circuits]
Anders Mikkelsen
November 19, 2024, 01:33:48 PM
post Re: Testing and teardown of a commercial induction heater
[Electronic Circuits]
DashApple
November 19, 2024, 08:02:30 AM
post Re: First DRSSTC, Full Bridge PCB & IGBT Selection question.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
November 19, 2024, 05:31:47 AM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
futurist
November 19, 2024, 02:33:42 AM
post Re: Testing and teardown of a commercial induction heater
[Electronic Circuits]
dejuli2
November 18, 2024, 11:19:28 PM
post Re: First DRSSTC, Full Bridge PCB & IGBT Selection question.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
November 18, 2024, 08:43:20 PM
post Re: Testing and teardown of a commercial induction heater
[Electronic Circuits]
DashApple
November 18, 2024, 06:07:11 PM
post Re: Is intentional overlap in the secondary theoretically possible?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
MinuteMylar
November 18, 2024, 05:04:09 PM
post Re: First DRSSTC, Full Bridge PCB & IGBT Selection question.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Beggernator.
November 18, 2024, 12:17:41 PM
post Re: Testing and teardown of a commercial induction heater
[Electronic Circuits]
dejuli2
November 18, 2024, 09:25:38 AM
post Re: First DRSSTC, Full Bridge PCB & IGBT Selection question.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
November 18, 2024, 01:09:10 AM
post Re: 160mm DRSSTC project
[Dual Resonant Solid State Tesla coils (DRSSTC)]
paulsimik
November 17, 2024, 11:36:52 PM
post Re: 160mm DRSSTC project
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mathieu thm
November 17, 2024, 10:28:23 PM
post Re: 160mm DRSSTC project
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
November 17, 2024, 10:13:44 PM

Sitemap 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 
SimplePortal 2.3.6 © 2008-2014, SimplePortal