Author Topic: First DRSSTC, No Sparks on Breakout  (Read 2054 times)

Online davekni

  • High Voltage Senior
  • *****
  • Posts: 693
  • Karma: +34/-0
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: First DRSSTC, No Sparks on Breakout
« Reply #40 on: August 21, 2020, 07:06:06 PM »
A quick simulation shows coupling factor of 0.152 matches your waveform well.  My DRSSTC design point was 0.151.  Unfortunately I had trouble with arcing from part-way-up my secondary at full power, so had to raise my secondary slightly farther, which reduced coupling for my coil to 0.142.  If it weren't for my arcing problem, I'd still be at 0.151.  Unless you build a higher-power bridge to drive it, I doubt your coil is going to have trouble with such mid-secondary arcing.  So I recommend not reducing coupling.  However, if your mechanical design allows easy raising of the secondary coil relative to primary, it doesn't hurt to experiment with coupling factor.

The higher primary current at low bus voltage indicates an efficient coil.  A perfect coil has no loss mechanisms except for arcs from the top.  Without arcs, current would ideally increase indefinitely.  The goal is to have arcs dissipate enough power to keep primary current below your limit.  My guess is that your design is on the edge there.  Good arcs will require close to 250A primary.  If you end up hitting your 250A limit too often, then you will need to raise primary impedance some (reduce primary capacitance and increase primary inductance).  It may be just fine as it is now, as long as the half-bridge is robust enough to handle almost 250A repeatedly.

Your waveform also indicates roughly-matched primary and secondary frequency.  That's best for low-power arcs as you can see.  At full power you will find better performance with slightly lower primary frequency (to match the dropping secondary frequency due to arc capacitance).
David Knierim

Offline Uspring

  • High Voltage Technician
  • ***
  • Posts: 197
  • Karma: +16/-0
  • Physicist
    • View Profile
Re: First DRSSTC, No Sparks on Breakout
« Reply #41 on: August 23, 2020, 07:19:34 PM »
acmq wrote:
Quote
The waveforms indicate too high coupling. The peaks of the output voltage don't have enough time to rise. With proper adjustments and light load the maximum voltage can be reached at the first beat, coinciding with a current notch.
Hi Antonio,

As you write in your paper about DRSSTCs, center frequency tuning optimises power transfer to the secondary and also allows zero current switching. But it has some problems, if you want to keep ZCS, while arcs change the secondary resonance frequency.
This is due to the way, phase shifts between driving voltage and primary current appear. In a standard serial tank the input impedance will look inductive, if the driving frequency is above resonance and capacitive, if below. The DRSSTC center frequency behaves the other way around. So it requires a PLL with inverted feedback, i.e. one, where the oscillator is decreased in frequency, if its phase lags against the reference (the primary current in our case).
That is possible, but in a dynamical situation, where, e.g. the arc requires lowering the driving frequency (since the secondary res f drops), the primary current comes early and the driving frequency must be lowered, i.e. switching will come late. That will involve hard switching to some extent. Hard switching also happens, when you simply keep the driving frequency constant.

It looks to me, that hard switching to some extent cannot be avoided for center frequency operation, even if a PLL is used.

Offline acmq

  • High Voltage Enthusiast
  • *
  • Posts: 15
  • Karma: +2/-0
    • View Profile
Re: First DRSSTC, No Sparks on Breakout
« Reply #42 on: August 25, 2020, 12:14:44 AM »
acmq wrote:
Quote
The waveforms indicate too high coupling. The peaks of the output voltage don't have enough time to rise. With proper adjustments and light load the maximum voltage can be reached at the first beat, coinciding with a current notch.
Hi Antonio,

As you write in your paper about DRSSTCs, center frequency tuning optimises power transfer to the secondary and also allows zero current switching. But it has some problems, if you want to keep ZCS, while arcs change the secondary resonance frequency.
This is due to the way, phase shifts between driving voltage and primary current appear. In a standard serial tank the input impedance will look inductive, if the driving frequency is above resonance and capacitive, if below. The DRSSTC center frequency behaves the other way around. So it requires a PLL with inverted feedback, i.e. one, where the oscillator is decreased in frequency, if its phase lags against the reference (the primary current in our case).
That is possible, but in a dynamical situation, where, e.g. the arc requires lowering the driving frequency (since the secondary res f drops), the primary current comes early and the driving frequency must be lowered, i.e. switching will come late. That will involve hard switching to some extent. Hard switching also happens, when you simply keep the driving frequency constant.

It looks to me, that hard switching to some extent cannot be avoided for center frequency operation, even if a PLL is used.

I am aware of the problem with PLL instability with drive at the central frequency. A possible solution is to use a comparator, with a wideband bandpass filter before it to filter out some noise and still keep proper phasing. With heavy load the central drive system naturally degrades to something similar to an impedance matching network and continues to work well. In my experiments I didn't use any feedback, and even so obtained reasonable results. With feedback, of course the switching is expected to be better. I stopped the experiments at quite long time ago, after realizing that my driver, built by my students when the designs were still primitive, had many problems requiring extensive modifications and a complete rebuild. Just yesterday I took the system from storage to see if it still works. It works, but I will probably not make the required changes. I will make a video from the measurements.
« Last Edit: August 26, 2020, 11:35:24 PM by acmq »

Offline acmq

  • High Voltage Enthusiast
  • *
  • Posts: 15
  • Karma: +2/-0
    • View Profile
Re: First DRSSTC, No Sparks on Breakout
« Reply #43 on: August 27, 2020, 12:02:00 AM »
Here is the video:
The coils were designed for complete energy transfer in 8.25 cycles, and perform as expected with excitation at 294 kHz. The system is not very powerful with the normal bus voltage of 170 V, and much less with 15 V, but is safe for measurements. It appears that the IGBTs are dropping too much voltage (the gate drive is too low anyway). Maybe there is a bad contact in the primary circuit.

High Voltage Forum

Re: First DRSSTC, No Sparks on Breakout
« Reply #43 on: August 27, 2020, 12:02:00 AM »

 


* Recent Topics and Posts

post Re: Have you ever tripped a breaker during normal operation ?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
panjaksli
December 02, 2020, 08:57:34 PM
post Re: Have you ever tripped a breaker during normal operation ?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
December 02, 2020, 08:17:09 PM
post Re: mini tesla (hopefully not a fail)
[Beginners]
davekni
December 02, 2020, 08:12:55 PM
post Re: Have you ever tripped a breaker during normal operation ?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
panjaksli
December 02, 2020, 07:34:53 PM
post Re: HF Litz wire as a primary coil
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
December 02, 2020, 07:14:18 PM
post Re: Have you ever tripped a breaker during normal operation ?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
December 02, 2020, 07:05:18 PM
post Re: Have you ever tripped a breaker during normal operation ?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
panjaksli
December 02, 2020, 06:58:40 PM
post Re: Have you ever tripped a breaker during normal operation ?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Max
December 02, 2020, 06:56:50 PM
post Re: Have you ever tripped a breaker during normal operation ?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
profdc9
December 02, 2020, 06:20:35 PM
post Re: Have you ever tripped a breaker during normal operation ?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
panjaksli
December 02, 2020, 05:24:23 PM
post Re: Have you ever tripped a breaker during normal operation ?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
buchtawill
December 02, 2020, 03:25:59 PM
post Re: Have you ever tripped a breaker during normal operation ?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
panjaksli
December 02, 2020, 03:02:01 PM
post Have you ever tripped a breaker during normal operation ?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
panjaksli
December 02, 2020, 01:36:04 PM
post Re: mini tesla (hopefully not a fail)
[Beginners]
bogdan
December 02, 2020, 08:55:06 AM
post Re: HF Litz wire as a primary coil
[Dual Resonant Solid State Tesla coils (DRSSTC)]
johnf
December 02, 2020, 07:43:14 AM
post Re: How to design FPGA based on EDA technology?
[Electronic Circuits]
Genterman
December 02, 2020, 06:53:52 AM
post Re: DRSSTC trouble
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
December 02, 2020, 03:29:14 AM
post Re: DRSSTC trouble
[Dual Resonant Solid State Tesla coils (DRSSTC)]
buchtawill
December 02, 2020, 02:43:33 AM
post Re: SKP DRSSTC = aliexpress driver + medium coil + large bricks ;)
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Maju
December 01, 2020, 10:44:31 PM
post Re: mini tesla (hopefully not a fail)
[Beginners]
davekni
December 01, 2020, 07:44:14 PM
post Re: transistor markings question
[Beginners]
davekni
December 01, 2020, 07:39:48 PM
post Re: HF Litz wire as a primary coil
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
December 01, 2020, 07:38:53 PM
post Re: How to design FPGA based on EDA technology?
[Electronic Circuits]
petespaco
December 01, 2020, 06:30:33 PM
post Re: Question about arduino polyphonic MIDI interrupter
[Dual Resonant Solid State Tesla coils (DRSSTC)]
bozidar
December 01, 2020, 04:58:29 PM
post Re: Question about arduino polyphonic MIDI interrupter
[Dual Resonant Solid State Tesla coils (DRSSTC)]
TMaxElectronics
December 01, 2020, 04:22:10 PM
post Re: Question about arduino polyphonic MIDI interrupter
[Dual Resonant Solid State Tesla coils (DRSSTC)]
bozidar
December 01, 2020, 03:02:51 PM
post Re: Half-brigde with pot on mosfet gates question
[Solid State Tesla Coils (SSTC)]
TMaxElectronics
December 01, 2020, 12:08:56 PM
post transistor markings question
[Beginners]
NOOBPASTE51
December 01, 2020, 12:02:19 PM
post Re: Question about arduino polyphonic MIDI interrupter
[Dual Resonant Solid State Tesla coils (DRSSTC)]
TMaxElectronics
December 01, 2020, 11:55:01 AM
post Re: HF Litz wire as a primary coil
[Dual Resonant Solid State Tesla coils (DRSSTC)]
TMaxElectronics
December 01, 2020, 11:50:19 AM
post Re: Analog HFBR amplifier
[Electronic Circuits]
TMaxElectronics
December 01, 2020, 11:21:56 AM
post Half-brigde with pot on mosfet gates question
[Solid State Tesla Coils (SSTC)]
costas_p
December 01, 2020, 11:17:16 AM
post Re: Question about arduino polyphonic MIDI interrupter
[Dual Resonant Solid State Tesla coils (DRSSTC)]
bozidar
December 01, 2020, 11:11:50 AM
post Re: mini tesla (hopefully not a fail)
[Beginners]
bogdan
December 01, 2020, 09:29:24 AM
post Re: HF Litz wire as a primary coil
[Dual Resonant Solid State Tesla coils (DRSSTC)]
johnf
December 01, 2020, 07:03:56 AM
post Re: How to design FPGA based on EDA technology?
[Electronic Circuits]
johnf
December 01, 2020, 06:49:26 AM
post Re: SSTC or DRSSTC with GaN Transistors
[Solid State Tesla Coils (SSTC)]
Steve Ward
December 01, 2020, 04:59:28 AM
post How to design FPGA based on EDA technology?
[Electronic Circuits]
Genterman
December 01, 2020, 04:02:06 AM
post Re: DRSSTC trouble
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
December 01, 2020, 03:46:10 AM
post Re: DRSSTC trouble
[Dual Resonant Solid State Tesla coils (DRSSTC)]
buchtawill
December 01, 2020, 02:00:54 AM
post Re: HF Litz wire as a primary coil
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Steve Ward
December 01, 2020, 01:47:10 AM
post Re: DRSSTC trouble
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
December 01, 2020, 12:02:23 AM
post Re: Site Info desperately needed: http://www.stevehv.4hv.org/
[General Chat]
Mads Barnkob
November 30, 2020, 10:28:56 PM
post Re: I started making a drsstc
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Miki_407
November 30, 2020, 08:58:41 PM
post DRSSTC trouble
[Dual Resonant Solid State Tesla coils (DRSSTC)]
buchtawill
November 30, 2020, 08:53:00 PM
post Re: I started making a drsstc
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
November 30, 2020, 08:49:30 PM
post Re: Simple H-Bridge construction with low parasitic inductances (for SSTC or ...)
[Beginners]
davekni
November 30, 2020, 08:45:46 PM
post Re: mini tesla (hopefully not a fail)
[Beginners]
davekni
November 30, 2020, 06:56:13 PM
post Re: I started making a drsstc
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Miki_407
November 30, 2020, 01:16:04 PM
post Re: I started making a drsstc
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
November 30, 2020, 12:56:05 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