Author Topic: Horrible waveforms advice--just bad test setup?  (Read 1008 times)

Offline GKnapp

  • High Voltage Enthusiast
  • *
  • Posts: 31
  • Karma: +0/-0
    • View Profile
Horrible waveforms advice--just bad test setup?
« on: July 21, 2021, 06:34:13 PM »
Hello all, trying to finally get a coil up and running. Finally put the primary and secondary on to check my feedback and primary phasing.

The coil works--starts oscillating at about 10 volts on the bus, and I can get about an inch spark to an object with 30 volts.

These are the G-E waveforms I'm getting. Before I put it all together with a primary and secondary for testing the feedback, I was getting not perfect, but acceptable square waves. I'm using an aliexpress ud1.3b so it has no phase lead, but seems to work quite well.

With it all put together, I'm getting these horrible things. My test setup isn't truly horrible, but it does have overly long primary wires so I can move them around. The gdt is pretty normal--15 turns or so of cat5 cables twisted together, and about as short as they can reasonably be to the transistors. Could these waveforms just be that my test setup has much too much leakage inductance, bad grounding, etc. or are they bad enough that it implies something else is wrong? Again, before I connected the primary and secondary, the waveforms were mostly okay.



« Last Edit: July 21, 2021, 06:50:46 PM by GKnapp »

Offline alan sailer

  • High Voltage Technician
  • ***
  • Posts: 166
  • Karma: +10/-0
    • View Profile
Re: Horrible waveforms advice--just bad test setup?
« Reply #1 on: July 21, 2021, 07:55:03 PM »
I can see one possible issue with the scope leads. Since there are such large magnetic fields
generated by the primary current you can easily induce voltages on any conducting  loop. The
loop formed  by the ground lead of the scope probe can be a problem. It would be a good idea
to wrap the ground lead around the body of the scope probe to minimize this loop.

Steve Ward wrote a great paper on the pitfalls of measuring DRSSTC wave-forms.

https://hobbydocbox.com/Radio/67533485-Testing-and-verification-waveforms-of-a-small-drsstc-part-1-steven-ward-6-24-2009.html

Cheers.

Offline davekni

  • High Voltage Expert
  • ******
  • Posts: 1791
  • Karma: +88/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: Horrible waveforms advice--just bad test setup?
« Reply #2 on: July 22, 2021, 06:50:07 AM »
Scope ground loop is a possibility as Alan mentioned.  However, I'd expect that to pick up mostly sine-wave field from primary current.  The distortion doesn't have that look.  I'd be more suspicious of a GDT phasing issue - one of the four outputs may have leads reversed.  It is possible that you got some output without running long enough to fry IGBTs.

Looks like the large white cap is your primary resonant capacitor.  What is the array of smaller rectangular capacitors on vectorboard, light gray in color?
David Knierim

Offline GKnapp

  • High Voltage Enthusiast
  • *
  • Posts: 31
  • Karma: +0/-0
    • View Profile
Re: Horrible waveforms advice--just bad test setup?
« Reply #3 on: July 22, 2021, 08:50:34 PM »
After some more testing, I think I must have grounding issues. Even with only one scope between g-e, the bridge was drawing too much power and not working (a different issue from last time..). Not sure why this would be--I'm using a dc bench supply for testing, so everything should be isolated... I know not to use two scopes at a time, but I was able to measure across both igbts, and one starts up on the pulse and the other down for the pulse, so I'd assume I'm good on gdt phasing.

On the principle that if I don't measure it it isn't a problem, I removed all scope probes and it seems to work fine. Draws very little power at 30v, and making about an inch spark to a screwdriver. Based on prior experience, I'd think this means I have all the feedback and other phasing right, as it shouldn't work nearly so well on only 30v if it weren't correct...

Dave, the little array of capacitors is between ground and the negative bus and ~.1uf--on Mads' site, he explains that this can help protect some electronics in cases where there is an arc-over or something by allowing an easy path for the high frequency ac.



Offline davekni

  • High Voltage Expert
  • ******
  • Posts: 1791
  • Karma: +88/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: Horrible waveforms advice--just bad test setup?
« Reply #4 on: July 23, 2021, 03:52:46 AM »
Quote
I know not to use two scopes at a time, but I was able to measure across both igbts, and one starts up on the pulse and the other down for the pulse, so I'd assume I'm good on gdt phasing.
Are you using two probes at a time?  If either probe is on a high-side IGBT Vge (grounded to a high-side emitter), that will cause problems.  One issue is if the other probe is grounded to a different IGBT emitter.  The other is that the 0.1uF from Vbus- to ground is about 8 ohms reactance at 200kHz, so is close to grounding Vbus-.  Yes, that Vbus- to ground capacitor is useful, though typically not necessary to use an array of capacitors.  You could disconnect it for low-voltage scoping.
David Knierim

Offline GKnapp

  • High Voltage Enthusiast
  • *
  • Posts: 31
  • Karma: +0/-0
    • View Profile
Re: Horrible waveforms advice--just bad test setup?
« Reply #5 on: July 23, 2021, 04:51:37 PM »
I should have said probes not scopes--i know not to use two at the same time, but it was having troubles even with one, which I found odd. I pulled off the secondary, and it had no issues, so I'm a little mystified. But it was all seeming to work and relatively in tune, so I tested it at about 60vac and it made pleasant sparks without drawing too much power so I think I'm good.

Would it be better to reduce the capacitance for that capacitor?

Also, I'm using a ud1.3b and I believe it has a 10ohm OCD resistor. I read that I shouldn't turn the pot voltage higher than 3.75 ish volts for that model, so I think I can't have an effective ocd with my current setup (aiming for max 300a, 289:1 current and feedback transformers). Do I need to parallel or replace that resistor with something lower--and is there a best  way for me to test the ocd? I only have a signal generator that goes to +-2.5 volts.

Offline davekni

  • High Voltage Expert
  • ******
  • Posts: 1791
  • Karma: +88/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: Horrible waveforms advice--just bad test setup?
« Reply #6 on: July 24, 2021, 03:20:42 AM »
Quote
Would it be better to reduce the capacitance for that capacitor?
0.1uF is fine, except if scoping a high-side Vge.  Even with a single probe, grounding a high-side emitter (an H-Bridge output) will cause problems.  A differential probe is best for scoping high-side Vge with Vbus powered even at low Vbus voltage.

Quote
Also, I'm using a ud1.3b and I believe it has a 10ohm OCD resistor. I read that I shouldn't turn the pot voltage higher than 3.75 ish volts for that model, so I think I can't have an effective ocd with my current setup (aiming for max 300a, 289:1 current and feedback transformers). Do I need to parallel or replace that resistor with something lower--and is there a best  way for me to test the ocd? I only have a signal generator that goes to +-2.5 volts.
Yes, you will need to reduce the 10ohm resistor to 3.75 ohms or a bit lower.  For testing, I'd run the coil with OCD set low.  If you want to check with the POT at 3.75V, test initially before reducing the 10ohm resistor value.  Then OCD will be ~120A.  Or, to test the final driver setup, loop the H-Bridge output lead through the CT 2 or 3 times (if the wire fits).  Then OCD will be 1/2 or 1/3rd of the final value.
David Knierim

High Voltage Forum

Re: Horrible waveforms advice--just bad test setup?
« Reply #6 on: July 24, 2021, 03:20:42 AM »

 


* Recent Topics and Posts

post Re: Recommended development boards for QCWDRSSTC
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
davekni
Today at 07:33:57 PM
post Re: Ud failure
[Dual Resonant Solid State Tesla coils (DRSSTC)]
FonziDaytona
Today at 07:06:33 PM
post What am I missing?!?!?
[Spark Gap Tesla Coils (SGTC)]
Conrad73
Today at 06:35:43 PM
post Radiometer Copenhagen OSG 42b Oscilloscope Repair, From The 1950'ish
[Laboratories, Equipment and Tools]
Mads Barnkob
Today at 03:18:22 PM
post Re: Recommended development boards for QCWDRSSTC
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Rafft
Today at 02:53:30 PM
post Recommended development boards for QCWDRSSTC
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
dru
Today at 09:05:37 AM
post Re: Ud failure
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
Today at 08:29:09 AM
post Re: Ud failure
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
Today at 05:27:41 AM
post Re: Gauss meter for strong magnetic fields
[Laboratories, Equipment and Tools]
klugesmith
Today at 02:12:21 AM
post Ud failure
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
Today at 01:50:45 AM
post Re: controlling the negative gate bias voltage of the Gate drive transformer
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 24, 2022, 09:36:58 PM
post UD2.x mod
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Rafft
September 24, 2022, 05:06:28 PM
post Re: Gate drive transformer with negative gate bias voltage
[Dual Resonant Solid State Tesla coils (DRSSTC)]
prabhatkumar
September 24, 2022, 06:56:35 AM
post Re: Gate drive transformer with negative gate bias voltage
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 24, 2022, 06:09:03 AM
post Re: Gauss meter for strong magnetic fields
[Laboratories, Equipment and Tools]
davekni
September 24, 2022, 01:32:08 AM
post Re: Some questions about my first drsstc.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
mthome4
September 23, 2022, 10:55:21 PM
post Re: Gauss meter for strong magnetic fields
[Laboratories, Equipment and Tools]
AstRii
September 23, 2022, 10:39:13 PM
post controlling the negative gate bias voltage of the Gate drive transformer
[Dual Resonant Solid State Tesla coils (DRSSTC)]
prabhatkumar
September 23, 2022, 05:48:17 PM
post Gauss meter for strong magnetic fields
[Laboratories, Equipment and Tools]
Peregrine
September 23, 2022, 02:01:10 PM
post Re: UD2.7 dual Purpose Use
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 23, 2022, 03:04:31 AM
post Re: UD2.7 dual Purpose Use
[Dual Resonant Solid State Tesla coils (DRSSTC)]
FonziDaytona
September 22, 2022, 04:15:36 PM
post Re: SSTC - PCB design
[Beginners]
Przemekk00
September 22, 2022, 12:39:51 PM
post Re: Possible Leads on Single Photon Camera
[General Chat]
alan sailer
September 22, 2022, 12:05:55 AM
post Re: Possible Leads on Single Photon Camera
[General Chat]
Mads Barnkob
September 21, 2022, 10:32:29 PM
post Possible Leads on Single Photon Camera
[General Chat]
alan sailer
September 21, 2022, 03:57:38 PM
post Re: Driverless Single Mosfet Relay interrupted SSTC? - [All kinds of problems]
[Solid State Tesla Coils (SSTC)]
davekni
September 21, 2022, 05:50:15 AM
post Re: Musical interrupter problems
[Solid State Tesla Coils (SSTC)]
RoamingD
September 20, 2022, 10:29:41 PM
post Re: Musical interrupter problems
[Solid State Tesla Coils (SSTC)]
Mads Barnkob
September 20, 2022, 08:24:30 PM
post Re: Driverless Single Mosfet Relay interrupted SSTC? - [All kinds of problems]
[Solid State Tesla Coils (SSTC)]
TiagoBS
September 20, 2022, 06:23:54 PM
post Re: Some questions about my first drsstc.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 20, 2022, 05:20:07 AM
post Re: TO247 mounting
[Beginners]
davekni
September 20, 2022, 05:15:35 AM
post Re: MidiStick V2.0: Next gen tesla coil interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
TMaxElectronics
September 19, 2022, 11:43:47 PM
post Re: TO247 mounting
[Beginners]
Weston
September 19, 2022, 09:58:56 PM
post Re: Some questions about my first drsstc.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
mthome4
September 19, 2022, 09:05:35 PM
post Re: Musical interrupter problems
[Solid State Tesla Coils (SSTC)]
RoamingD
September 19, 2022, 12:58:35 PM
post Re: UD2.7 dual Purpose Use
[Dual Resonant Solid State Tesla coils (DRSSTC)]
FonziDaytona
September 19, 2022, 12:13:46 AM
post Re: MMC capacitor crash
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 19, 2022, 12:09:22 AM
post Re: UD2.7 dual Purpose Use
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 18, 2022, 11:38:51 PM
post Re: UD2.7 dual Purpose Use
[Dual Resonant Solid State Tesla coils (DRSSTC)]
FonziDaytona
September 18, 2022, 10:41:54 PM
post Re: Musical interrupter problems
[Solid State Tesla Coils (SSTC)]
davekni
September 18, 2022, 10:31:32 PM
post Re: Musical interrupter problems
[Solid State Tesla Coils (SSTC)]
RoamingD
September 18, 2022, 10:09:33 PM
post Re: UD2.7 dual Purpose Use
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 18, 2022, 09:58:34 PM
post Re: UD2.7 dual Purpose Use
[Dual Resonant Solid State Tesla coils (DRSSTC)]
FonziDaytona
September 18, 2022, 08:45:21 PM
post Re: Musical interrupter problems
[Solid State Tesla Coils (SSTC)]
Mads Barnkob
September 18, 2022, 07:55:11 PM
post Re: Syntherrupter - A Feature-rich, Polyphonic Interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Max
September 18, 2022, 07:25:30 PM
post TO247 mounting
[Beginners]
mthome4
September 18, 2022, 06:32:10 PM
post Musical interrupter problems
[Solid State Tesla Coils (SSTC)]
RoamingD
September 18, 2022, 05:48:17 PM
post Re: UD2.7 dual Purpose Use
[Dual Resonant Solid State Tesla coils (DRSSTC)]
FonziDaytona
September 18, 2022, 05:44:14 PM
post Re: MMC capacitor crash
[Dual Resonant Solid State Tesla coils (DRSSTC)]
JCF
September 18, 2022, 05:22:31 PM
post Re: UD2.7 dual Purpose Use
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 18, 2022, 06:10:33 AM
post Re: UD2.7 dual Purpose Use
[Dual Resonant Solid State Tesla coils (DRSSTC)]
FonziDaytona
September 18, 2022, 12:47:41 AM
post Re: Some questions about my first drsstc.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 17, 2022, 06:37:23 PM
post Re: Some questions about my first drsstc.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
mthome4
September 17, 2022, 11:56:26 AM
post Re: Some questions about my first drsstc.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 17, 2022, 01:50:27 AM
post Re: Some questions about my first drsstc.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
mthome4
September 16, 2022, 11:05:46 PM
post Re: MMC capacitor crash
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
September 16, 2022, 09:48:56 PM
post Re: MMC capacitor crash
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 16, 2022, 09:04:59 PM
post Re: MMC capacitor crash
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
September 16, 2022, 08:32:01 PM
post Re: MMC capacitor crash
[Dual Resonant Solid State Tesla coils (DRSSTC)]
JCF
September 16, 2022, 04:17:31 PM
post Re: MMC capacitor crash
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 16, 2022, 05:40:05 AM
post Re: Getting last joules out of batteries
[Laboratories, Equipment and Tools]
klugesmith
September 15, 2022, 11:18:56 PM
post Re: SALE(US) - 30 amp 3 phase GE volt-pac variac auto transformer 0-520v
[Sell / Buy / Trade]
rikkitikkitavi
September 15, 2022, 10:16:03 PM
post Re: MMC capacitor crash
[Dual Resonant Solid State Tesla coils (DRSSTC)]
JCF
September 15, 2022, 04:15:12 PM
post Re: MMC capacitor crash
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 15, 2022, 05:54:55 AM
post Re: Getting last joules out of batteries
[Laboratories, Equipment and Tools]
Weston
September 14, 2022, 10:36:37 PM
post Re: Help with PLL induction heater driver
[Electronic Circuits]
dbach
September 14, 2022, 09:09:09 PM
post Re: Few questions before a TC show
[Dual Resonant Solid State Tesla coils (DRSSTC)]
AstRii
September 14, 2022, 06:47:04 PM
post Re: The most powerful Russian Tesla coil in Europe (and maybe in the world)
[Dual Resonant Solid State Tesla coils (DRSSTC)]
hammertone
September 14, 2022, 04:45:43 PM
post Re: MMC capacitor crash
[Dual Resonant Solid State Tesla coils (DRSSTC)]
JCF
September 14, 2022, 03:43:03 PM
post Re: SSTC - PCB design
[Beginners]
davekni
September 14, 2022, 06:38:17 AM
post Re: Sources for optical parts?
[Light, Lasers and Optics]
klugesmith
September 14, 2022, 02:16:33 AM
post Re: Circuit drawing software for dummies
[Printed Circuit Board]
Twospoons
September 14, 2022, 12:31:44 AM
post Re: Sources for optical parts?
[Light, Lasers and Optics]
Twospoons
September 13, 2022, 10:21:13 PM
post Re: The most powerful Russian Tesla coil in Europe (and maybe in the world)
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
September 13, 2022, 10:20:28 PM
post Re: Where to find a "small" focal spot x-ray tube
[X-ray]
Fijcho
September 13, 2022, 10:05:48 PM
post Re: MMC capacitor crash
[Dual Resonant Solid State Tesla coils (DRSSTC)]
JCF
September 13, 2022, 06:00:00 PM
post Re: Sources for optical parts?
[Light, Lasers and Optics]
klugesmith
September 13, 2022, 05:37:54 PM
post Re: Few questions before a TC show
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
September 13, 2022, 10:23:49 AM
post Re: The most powerful Russian Tesla coil in Europe (and maybe in the world)
[Dual Resonant Solid State Tesla coils (DRSSTC)]
TeslaFX_rus
September 13, 2022, 09:59:45 AM
post Sources for optical parts?
[Light, Lasers and Optics]
Twospoons
September 13, 2022, 07:36:43 AM
post Re: Some questions about my first drsstc.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 13, 2022, 03:43:58 AM
post Re: Circuit drawing software for dummies
[Printed Circuit Board]
LoOdaK
September 12, 2022, 09:45:41 PM
post Re: Some questions about my first drsstc.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
mthome4
September 12, 2022, 08:09:42 PM
post Re: Circuit drawing software for dummies
[Printed Circuit Board]
Mads Barnkob
September 12, 2022, 04:34:54 PM
post Re: Some questions about my first drsstc.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Maju
September 12, 2022, 04:32:03 PM
post Re: SSTC - PCB design
[Beginners]
Przemekk00
September 12, 2022, 03:00:32 PM
post Re: Circuit drawing software for dummies
[Printed Circuit Board]
LoOdaK
September 12, 2022, 02:26:47 PM
post Re: Circuit drawing software for dummies
[Printed Circuit Board]
Mads Barnkob
September 12, 2022, 01:09:53 PM
post Few questions before a TC show
[Dual Resonant Solid State Tesla coils (DRSSTC)]
AstRii
September 12, 2022, 12:52:58 PM
post Re: Circuit drawing software for dummies
[Printed Circuit Board]
Twospoons
September 12, 2022, 07:20:11 AM
post Re: Help with PLL induction heater driver
[Electronic Circuits]
petespaco
September 12, 2022, 04:48:21 AM
post Circuit drawing software for dummies
[Printed Circuit Board]
abstruse1
September 12, 2022, 03:33:52 AM
post Help with PLL induction heater driver
[Electronic Circuits]
dbach
September 12, 2022, 02:28:17 AM
post Re: QCW music with Midi
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyglas
September 11, 2022, 11:32:31 PM
post SALE(US) - 30 amp 3 phase GE volt-pac variac auto transformer 0-520v
[Sell / Buy / Trade]
pache11
September 11, 2022, 10:31:06 PM
post Re: Question about Flip-Flop wiring for DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
bockett
September 11, 2022, 10:28:43 PM
post Re: Question about Flip-Flop wiring for DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
September 11, 2022, 10:15:59 PM
post Re: UV-cured cyanoacrylate glues?
[Light, Lasers and Optics]
pache11
September 11, 2022, 10:05:44 PM
post Re: CO2 laser refurbishing
[Light, Lasers and Optics]
pache11
September 11, 2022, 09:57:35 PM
post Re: Question about Flip-Flop wiring for DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
bockett
September 11, 2022, 09:24:04 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