Author Topic: my first DRSSTC is not working properly  (Read 392 times)

Offline zanikk

  • High Voltage Enthusiast
  • *
  • Posts: 2
  • Karma: +0/-0
    • View Profile
my first DRSSTC is not working properly
« on: November 18, 2019, 06:56:18 PM »
Hello.
I'm making my first DRSSTC and I'm having some problems. :(

here are some pics and details
/im using one tesla interrupter with a 250us/
coil





full bridge: CM200DY-12H



MMC: 6 strings in parallel of 2 in series Cornell Dubilier , 0.45uf


well , the first problem is that i have a strange waveform coming out of  the bidge , the current wave form looks good for me but the voltage looks very strange, I have  already tested the bridge with a fixed square wave on the feedback input and i got a really nice square wave on the output so i think the bridge works well.





 The second problem its that i'm geting  5/7cm sparks when i put the ground cable near the topload (at 50v dc) , i tested with 100v and 200v dc but eny sparks jump out of the breakout point :(
/>
Thanks for helping :)
« Last Edit: November 18, 2019, 07:07:26 PM by zanikk »

Offline davekni

  • High Voltage Technician
  • ***
  • Posts: 131
  • Karma: +5/-0
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: my first DRSSTC is not working properly
« Reply #1 on: November 19, 2019, 06:17:03 AM »
For the voltage waveform, I'd guess it's distorted by inductive voltage drop in the ground.  If you can ground the scope probe at the IGBT brick and measure the bridge output voltage near by on the same brick, you'll likely see less distortion.

My first guess for low performance is mismatched primary-to-secondary frequency.  But that's entirely a guess.

Hopefully you'll get more responses from others here who have built more similar coils.
David Knierim

Offline Mads Barnkob

  • Administrator
  • High Voltage Expert
  • *****
  • Posts: 1180
  • Karma: +17/-0
  • Denmark
    • View Profile
    • Kaizer Power Electronics
Re: my first DRSSTC is not working properly
« Reply #2 on: November 20, 2019, 10:25:09 AM »
Hi Zanikk and welcome to HVF :)

First off, it looks like a really well built coil and setup overall, you have done your home work.

What is the resonant frequency of your secondary + topload? What is the resonant frequency of your primary tap point + MMC?

It looks like you are using some regular 3 pin current transformers used for maybe 50 Hz mains current sensing? What are those two black current monitors? Since you say it works at low voltage, but at higher it stops working, maybe you are saturating those current transformers?

Another simple test, have you tried to reverse the polarity of the primary wires or feedback transformer?

Low voltage testing can be misleading due to IGBT output capacitance being relative to C-E voltage, the higher voltage the lower output capacitance, so you will always see higher switching spikes at low voltages, yours looks a bit over damped so its actually a slow charging instead, just guess work.
http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

Offline zanikk

  • High Voltage Enthusiast
  • *
  • Posts: 2
  • Karma: +0/-0
    • View Profile
Re: my first DRSSTC is not working properly
« Reply #3 on: November 20, 2019, 06:07:23 PM »
Thanks for the tips, the same thing happened to another guy , so i think im going to ground the scope :) .
The resonant frequency of the secondary + topload its 71.4khz and the resonance of the  primary +MMC its 69.2khz.
The current transformers are CST206-1A (100:1) ,i saw a guy on youtube that use those ct at 100khz with 350vdc on the bridge so...
(The primary circuit still oscillating at 200vdc)
if I reverse the feedback CT the coil starts oscillating at 9khz and I don’t see eny current on the primary  :-\ .
Could be something with the gdt? I saw a peak voltage of 10v and im running it with ucc37321/2 at 15v peak ,im just thinking that im running the igbt at linear region , thats bad for the igbts i think.
Yesterday i had tried to make a new gdt (1:2:2:2:2) , but seems very difficult to wind , could i use two gdts (1:2:2), one for each half bridge, instead of one gdt for the full bridge ? I apreciate your help :)

Offline Mads Barnkob

  • Administrator
  • High Voltage Expert
  • *****
  • Posts: 1180
  • Karma: +17/-0
  • Denmark
    • View Profile
    • Kaizer Power Electronics
Re: my first DRSSTC is not working properly
« Reply #4 on: November 20, 2019, 08:18:32 PM »
I would not put my money on those current transformers (even though they are free from many kinds of power electronics). I attached the datasheet, for 70 kHz you are looking at some 40-50% derating of the V/uS rating and it is only specified up to 110Arms (~150Apeak) which is way too low for a DRSSTC, a coil like yours is able to push some 500-800 Apeak.

GDTs are very easy to make with CAT5 network cable, you can see how I did + calculations here: http://kaizerpowerelectronics.dk/tesla-coils/kaizer-drsstc-i/ stick with 1:1:1:1:1. Which leads me to another question, what kind of driver are you using? If you only have UCC driver chips on the output stage that is too weak for driving bricks!

Are your bricks heating up? Since you suspect linear operation only? Do not fear too much about IGBTs getting damaged from that, they can dissipate a lot of power. If you can touch the heat sink there is not a problem.

http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

Offline klugesmith

  • High Voltage Experimenter
  • **
  • Posts: 85
  • Karma: +4/-0
    • View Profile
Re: my first DRSSTC is not working properly
« Reply #5 on: November 20, 2019, 09:06:08 PM »
Thanks for sharing the CT datasheet, Mads.

The volt-seconds limit (ET maximum) is about core saturation, which gets worse at low frequencies.  [edit] Maybe also core loss & temperature rise, which gets worse at high frequencies. At any frequency you can reduce ET by using a smaller burden resistor.  Same primary & secondary currents, smaller voltages, so less magnetization & loss in the core. [\edit]

What do veteran coilers have to say about Rogowski coils for getting quantitative current waveforms?
No saturation, because no iron.  I guess that for the narrowband, high frequency of a TC,  it's easy to get plenty of sensitivity, and you could even skip the voltage integration step (so scope waveform is proportional to di/dt).

The wikipedia page about Rogowski coils starts out with a definition that's too narrow.  Coil does not have to be helical with return winding along the axis; that's just a popular way for DIY'ers to make them from coaxial cable.  I have some multilayer PC-board Rogowski coils, made in a waste section of a circuit board for work. Would love to send one to a competent coiler for experiments. Not the same as the stock picture attached here.
« Last Edit: November 21, 2019, 01:21:45 AM by klugesmith »

Offline Uspring

  • High Voltage Technician
  • ***
  • Posts: 122
  • Karma: +9/-0
  • Physicist
    • View Profile
Re: my first DRSSTC is not working properly
« Reply #6 on: November 21, 2019, 02:48:18 PM »
Probably the biggest disadvantage of a coreless CT is the requirement of a much lower burden resistor R due to the reduced inductance. In order to get a low phase shift between input and output current R << Reactance of L.

Offline Hydron

  • Administrator
  • High Voltage Engineer
  • *****
  • Posts: 273
  • Karma: +8/-0
    • View Profile
Re: my first DRSSTC is not working properly
« Reply #7 on: November 21, 2019, 08:04:53 PM »
I've had a quick play around with Rogowski coils, though my aims were more to make something that could fit around a TO-247 leg. It quickly became apparent that I needed to put in more time into it than I had available though, so not much to report other than it's not necessarily easy to shield one from E-fields. Gotta be possible though, as there are commercial devices out there designed to do exactly what I want (at a crazy price), sadly without much info from patents, teardowns etc. Like you I also intend to make a PCB one at some point - for the lazy there are even Altium design files for one floating around on the TI website (as part of an app-note of theirs).

As for those CTs, I haven't crunched the numbers but if they are getting pushed too hard then you can always make a cascade using another ferrite core with say 10 turns as a primary, then run one of those turns through the small CTs so that the ratios multiply to get 1000:1. If you keep the same V/A sensitivity (by increasing the burden R) you won't gain any margin in saturation on the small ones, but you will reduce the likelihood of parasitics ruining your day, so you likely can live with a lower sensitivity and thus a lower chance of saturation.

High Voltage Forum

Re: my first DRSSTC is not working properly
« Reply #7 on: November 21, 2019, 08:04:53 PM »

 


* Recent Topics and Posts

post Re: Unusual polarized non-electrolytic energy discharge capacitor
[Capacitor banks]
T3sl4co1l
Today at 05:45:54 AM
post Re: Modern go-to switching devices
[Beginners]
T3sl4co1l
Today at 05:37:17 AM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
davekni
Today at 05:26:41 AM
post Re: Modern go-to switching devices
[Beginners]
klugesmith
Today at 04:54:15 AM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
John123
Today at 02:30:40 AM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
jturnerkc
Today at 02:21:19 AM
post Re: Aethra CCD Webcam Teardown - From Back When Streaming Was Expensive!
[Electronic circuits]
John123
Today at 02:14:48 AM
post Modern go-to switching devices
[Beginners]
John123
Today at 01:54:55 AM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
John123
Today at 01:37:03 AM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
jturnerkc
Today at 12:57:15 AM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
MRMILSTAR
December 13, 2019, 11:48:12 PM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
jturnerkc
December 13, 2019, 11:19:27 PM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
John123
December 13, 2019, 11:00:18 PM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
jturnerkc
December 13, 2019, 10:50:03 PM
post Re: Unusual polarized non-electrolytic energy discharge capacitor
[Capacitor banks]
MRMILSTAR
December 13, 2019, 10:46:20 PM
post Re: Unusual polarized non-electrolytic energy discharge capacitor
[Capacitor banks]
klugesmith
December 13, 2019, 10:31:03 PM
post Re: Unusual polarized non-electrolytic energy discharge capacitor
[Capacitor banks]
AndreiRS
December 13, 2019, 10:00:04 PM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
John123
December 13, 2019, 09:08:28 PM
post Unusual polarized non-electrolytic energy discharge capacitor
[Capacitor banks]
MRMILSTAR
December 13, 2019, 09:06:47 PM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
MRMILSTAR
December 13, 2019, 08:56:27 PM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
jturnerkc
December 13, 2019, 05:05:55 PM
post Re: How do you keep in contact with forum people...?
[General chatting]
Mads Barnkob
December 13, 2019, 09:31:58 AM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
johnf
December 13, 2019, 07:56:39 AM
post Re: Royer oscillator (ZVS) driven Jacob's ladder, E80 core transformer
[Transformer (ferrite core)]
AndreiRS
December 13, 2019, 03:59:49 AM
post How do you keep in contact with forum people...?
[General chatting]
AndreiRS
December 13, 2019, 03:23:31 AM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
klugesmith
December 13, 2019, 12:16:53 AM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Laci
December 12, 2019, 08:35:24 PM
post Re: How To Make a Stencil For Spray Paint With Cheap Hand Tools
[General chatting]
johnf
December 12, 2019, 07:53:35 PM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
John123
December 12, 2019, 02:52:58 PM
post Re: Royer oscillator (ZVS) driven Jacob's ladder, E80 core transformer
[Transformer (ferrite core)]
John123
December 12, 2019, 02:42:19 PM
post Re: Full bridge much "weaker" than half bridge?
[Solid state Tesla coils]
nick
December 12, 2019, 11:17:36 AM
post Re: Royer oscillator (ZVS) driven Jacob's ladder, E80 core transformer
[Transformer (ferrite core)]
davekni
December 12, 2019, 04:51:08 AM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
davekni
December 12, 2019, 04:26:22 AM
post Re: How To Make a Stencil For Spray Paint With Cheap Hand Tools
[General chatting]
AndreiRS
December 12, 2019, 01:21:35 AM
post Re: Using same winding on separate rails?
[Transformer (iron core)]
Twospoons
December 11, 2019, 10:49:04 PM
post Re: A dynamical arc model v2
[Dual Resonant Solid State Tesla coils]
Uspring
December 11, 2019, 05:28:46 PM
post Re: Full bridge much "weaker" than half bridge?
[Solid state Tesla coils]
Fumeaux
December 11, 2019, 03:11:42 PM
post Re: Royer oscillator (ZVS) driven Jacob's ladder, E80 core transformer
[Transformer (ferrite core)]
John123
December 11, 2019, 02:22:10 PM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
John123
December 11, 2019, 02:09:19 PM
post Full bridge much "weaker" than half bridge?
[Solid state Tesla coils]
nick
December 11, 2019, 01:10:57 PM
post Re: Possible use for large inductor (laminated core)
[Transformer (iron core)]
kamelryttarn
December 11, 2019, 08:48:36 AM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
davekni
December 11, 2019, 06:08:48 AM
post Re: SSTC low voltage at gate transformer and heating drivers
[Solid state Tesla coils]
davekni
December 11, 2019, 05:38:17 AM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
davekni
December 11, 2019, 05:01:31 AM
post Re: Using same winding on separate rails?
[Transformer (iron core)]
John123
December 11, 2019, 01:52:43 AM
post Re: Using same winding on separate rails?
[Transformer (iron core)]
klugesmith
December 11, 2019, 01:41:04 AM
post Re: Worlds Weirdest Microwave Oven, From A Weapons Factory - The Husqvarna Cupol
[Transformer (iron core)]
klugesmith
December 11, 2019, 01:37:13 AM
post Re: Using same winding on separate rails?
[Transformer (iron core)]
John123
December 11, 2019, 01:19:58 AM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
jturnerkc
December 11, 2019, 01:14:32 AM
post Re: Using same winding on separate rails?
[Transformer (iron core)]
klugesmith
December 11, 2019, 01:04:08 AM

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