Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - Jesperb123

Pages: [1]
1
Hi Hydron!
I'm sure that would help alot considering i'm starting from scratch  :)

2
Your simulation grounds the bottom of C2/C3/R1.  That is modelling a shorted GDT.
I tried using inductances to model the GDT but I didn't get it to work so I just grounded the node. I will have to try it again.


you have surmised correctly what the diode is for.
C2, C3 are to capacitively couple the GDT to avoid core walk hence saturation due to DC offset they are sufficiently high in value to make sure that no resonances are present near the operating frequency, R11 is a "Q" killer for the same reason acting as a snubber to quench ringing

That seems complicated but now I know what to google atleast. Thanks alot!

3
Hi everyone!

I've been trying my best to understand the schematic for Steve Wards 1.3b driver, but i'm having a hard time understanding the output stage to the GDT. I've used LTspice with some some similar mosfets (they're rated for Vds of -60V and 60V and have a similar gate charge - I couldn't find the L/W/Kp/lambda for the actual mosfets).



These are my conclusions so far (please tell me if i'm wrong):
The additional mosfets connected externally to the UCC2743 are used to switch a higher output voltage than what the UCC can provide. There are two push/pull pairs that work together so we can send current both ways through the GDT - which creates alternating voltages on the GDT secondaries.

I simulated the top pair with this schematic:


Here are the traces:


From this I've gathered that C1 and R2 are used to generated the pulse (the top most trace). The green trace is the voltage source that goes from 9V to 0V after 1ms. Initally the voltage at the node n1 is 24V (when the supply is high) since no current flows through the cap/resistor, but when the supply goes low the voltage at this node drops since the C1 begins charging through R1 (and R1s voltage drop brings down V(n1)). M2 briefly starts to conduct when n1 goes below some thresholdvoltage, and stops conducting when C1's charge is high enough to pull the n1 voltage above M2s threshold voltage. This genereates the positive pulse (while the other part of the circuit generates the negative pulse). Here comes a million questions :D

What purpose does the diode have? is it to limit the voltage at n1 to less than 24+a diode drop?
Another thing I don't understand is the capacitors in the output path (C3 and C2). They seem to increase the fall time of the purple output trace (compared to running the simulation without them). Do I need to choose values for these?

Also, Steve's schematic show mosfets with body diodes across the drain and the source of the mosfets. I presume these are important when we are driving an inductive load but the suggested mosfets (STB16NF06 Nfet and SPB18P06 G Pfet) doesn't seem to have these. Is this some intrinsic property of all mosfets? What am I missing?

Last question: Why does the UCC state that it can provide 4A of output current, but it doesn't mention the output voltage at which it can do this?

Best regards
Jesper Bolin

4
So I've been doing some searching around and found these for 4,12 euro:
Wima FKP4U031507H00KYSD

They have:
  • high dv/dt = 9000V/us
  • very low dissapation factor (<6*10^-4)
  • 2kVdc
  • Negative temperature coefficient for capacitance ==> Xc becomes larger for increasing temperature, better currentsharing?

So I think I should be able to use them in a 2S*2P configuration.

5
Hi hydron!
Ok then I understand why 2 in series might not be enough. I calculated the voltage across the MMC with:

Vpeak = Zc * Ipeak and since Zc is almost equal to abs(Xc) if the esr is low I get:
Vpeak = abs(Xc)* Ipeak

plugging in the numbers abs(Xc) = 5.25 ohms and Ipeak = 500A I get
Vpeak ≈ 2620V.

Using the Vdc rating for the caps mentioned earlier gave me 2*2000V = 4kV. But I guess what you mentioned about Vdc not being equal to Vac shows why two in series might not be enough.

That said, regarding DC voltage rating I haven't run the numbers on your coil but I am a little surprised that you think you can get away with only two of those caps in series. Maybe worth looking at a 3S * 3P config to give the same 0.15uF but at higher voltage and current. Also consider using cheaper caps and more of them - the CD parts you're looking at are overkill for a DRSSTC (their popularity is due to their success in spark-gap coils, though if you have them already there's no reason not to use them!).

Then I'll try to find some other capacitors that might work. Thanks alot for your help.

6
Just a quick question

How come we use the Vdc rating when selecting capacitors for the MMC? I think I'll use the 942C20P15K-F (2 parallel strings of 2 caps in series) and the datasheet states that they have a Vdc of 2kV while Vac is only 600V.

Edit: After calculating the RMS current (ontime = 200uS, BPS = 200, Ipk =500A) I get 50A, which the previous (2 parallel strings of 2 caps in series) MMC wouldn't be able to handle. I would need 4 strings of 2 capacitors in series to get the RMS-current rating up, but then I'd have too much capacitance (0.3uF instead of 0.15uF) which would mean I would need a fewer turns on my primary. I'd like to be able to run the teslacoil long enough to play music on it eventually, so I believe I have to take the RMS current rating seriously?

7
Hi Mads!
Thanks for the warm welcome and your guides, I would not have started this project if it wasn't for them :D

Maybe i'm dull but the coil you linked is way bigger than mine. Did you make a smaller version of it?

My small DRSSTC3 ( http://kaizerpowerelectronics.dk/tesla-coils/kaizer-drsstc-iii/ ) peaks at about 300'ish Ampere primary peak current. So for your coil that is about 1/3 larger, I would go with 400A for the OCD settings and design it for 500A to have some 20% headroom.

Then i'll design the bridge and MMC with this in mind. Yesterday I read the threads in the "DRRSTC information and other valuable thread archive", and it seems like one either has to use proper IGBT bricks or multiple TO-247 IGBT's to build the bridge. I'll have to do some more research before I can come to a conclusion, but I've read that IGBTs aren't really suited for high switching speeds, and since my resonant frequency is quite high i'm wondering if I might have to use mosfets instead?

High impedance = low cost.
+ Lower peak currents, overall construction can slack more
+ Smaller and cheaper MMC
+ Smaller and maybe cheaper IGBTs
- Higher switching losses

I'll keep this in mind.

Did you play around with the MMC calculator? http://kaizerpowerelectronics.dk/calculators/mmc-calculator/

I've just started taking a look at it. I'm sure it will be very useful when designing the MMC.

8
If you haven't made your primary too permanent, i would recommend you to use at least 7 turns, to increase inductance so you can decrease capacitance of your MMC. This will result in smaller peak currents, larger ontimes and it's more budget-friendly.

Hi!
Thanks alot for the reply  :D
Since i'm only in the planning stage I can still change alot about the project. The suggested change seems like a good idea. If i use 0.15uF instead of 0.45uF i'll need about 4.12uH from the primary, which according to this calculator (https://www.circuits.dk/flat-spiral-coil-inductor/)  (with the same pipediameter and spacing) I would need at most 5 turns. Is there some other reason for why would I would need more turns? or should I choose a smaller capacitance which increases the turns required?

You can calculate that easily; Xc = 1/(2*pi*f*C) , Vpk = Xc * Ipk

This was why I was struggling. I if I don't know Ipk I can't choose the right voltage rating on the caps for example. Is there some calculation one can do to find the peak current or is it impossible? (sparkloading?). Is 300A a good Ipk number to design MMC and transistors around?

9
Hi!
I'm planning on building a small DRSSTC, but my progress has slowed to a halt. I've tried my best to follow Mads Barnkob's guide on kaizerpowerelectronics.dk to determine some of the parameters:

Secondary design:
75mm diameter secondary
375mm tall
1700 turns (0.2mm cablediameter)

Topload
shape: toroid
Rminor = 3.75cm
Rmajor = 18.75cm

Primary
shape:flat spiral coil
4 turns
86mm inner diameter
10mm inbetween turns
6mm copperpipe with 1mm thickness
tapped at around 3 turns if 0.45uF capacitance is used (to match fres of secondary LC-circuit)


This should give a resonantfrequency of 202.5kHz and a reactance of 50k at resonantfrequency. I've read that 0.15uF to 0.45uF capacitance is suitable for a coil  of this size (http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/mmc-tank-capacitor/). Here's my problem: I need to know how large the current (peak and RMS) in the primary LC-circuit will be to determine which capacitors to use, but I have no idea how to come up with these values. Since i'm on a relatively small budget I figured that the transistors i use will put an upper limit on this value. Some people seem to go about it this way: select a peak current and then design a MMC (and buy transistors) that can handle this current. Since i've got no prior experience with DRSSTCs I don't know what kind of currents I can expect to run in a system like this, hence why i'm stuck.

 If anyone could point me in the right direction I would be very grateful.
//Jesper




Pages: [1]

* Recent Topics and Posts

post Re: Drsstc Driver Board for Tesla Coil Driver Optic Fiber Splice
[Dual Resonant Solid State Tesla coils (DRSSTC)]
iw1esu
Today at 01:56:54 PM
post Cap Identification 64KV
[Capacitor Banks]
Thermionix
Today at 07:14:33 AM
post Re: ZVS driven Plasma Ball (w/ segmented PTFE Secondary)
[Transformer (Ferrite Core)]
zytra
Today at 05:20:21 AM
post Re: ZVS driven Plasma Ball (w/ segmented PTFE Secondary)
[Transformer (Ferrite Core)]
klugesmith
Today at 03:44:12 AM
post Re: ZVS driven Plasma Ball (w/ segmented PTFE Secondary)
[Transformer (Ferrite Core)]
davekni
Today at 03:31:35 AM
post Re: ZVS driven Plasma Ball (w/ segmented PTFE Secondary)
[Transformer (Ferrite Core)]
zytra
Today at 03:01:47 AM
post Re: Cold Gas Satellite Thruster
[General Chat]
klugesmith
Today at 02:53:23 AM
post Re: ZVS driven Plasma Ball (w/ segmented PTFE Secondary)
[Transformer (Ferrite Core)]
davekni
Today at 02:52:00 AM
post Cold Gas Satellite Thruster
[General Chat]
Patrick
Today at 02:02:40 AM
post Re: Segmented PTFE Secondary, Large Plasma Ball project
[Transformer (Ferrite Core)]
zytra
Today at 01:04:03 AM
post Re: Segmented PTFE Secondary, Large Plasma Ball project
[Transformer (Ferrite Core)]
davekni
Today at 12:39:10 AM
post Re: Segmented PTFE Secondary, Large Plasma Ball project
[Transformer (Ferrite Core)]
zytra
January 19, 2021, 11:13:22 PM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
AeraCura_
January 19, 2021, 10:45:50 PM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
N1G3L
January 19, 2021, 09:17:18 PM
post Re: Alcatel Lucent B4 RRH2x60-4R teardown and reverse engineering
[Radio Frequency]
Da_Stier
January 19, 2021, 06:20:10 PM
post Fusor power supply
[Voltage Multipliers]
hammertone
January 19, 2021, 05:27:02 PM
post Re: Just a noob with some HV concerns...
[Beginners]
MrScrOggs
January 19, 2021, 01:21:13 PM
post Re: Just a noob with some HV concerns...
[Beginners]
klugesmith
January 19, 2021, 07:04:16 AM
post Re: Segmented PTFE Secondary, Large Plasma Ball project
[Transformer (Ferrite Core)]
zytra
January 19, 2021, 06:37:53 AM
post Re: Segmented PTFE Secondary, Large Plasma Ball project
[Transformer (Ferrite Core)]
davekni
January 19, 2021, 06:16:41 AM
post Re: Segmented PTFE Secondary, Large Plasma Ball project
[Transformer (Ferrite Core)]
zytra
January 19, 2021, 05:00:50 AM
post Re: Segmented PTFE Secondary, Large Plasma Ball project
[Transformer (Ferrite Core)]
davekni
January 19, 2021, 04:03:12 AM
post Just a noob with some HV concerns...
[Beginners]
MrScrOggs
January 19, 2021, 03:07:11 AM
post Re: Segmented PTFE Secondary, Large Plasma Ball project
[Transformer (Ferrite Core)]
zytra
January 19, 2021, 02:57:27 AM
post Re: compact midi interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
TMaxElectronics
January 19, 2021, 12:06:44 AM
post Re: Segmented PTFE Secondary, Large Plasma Ball project
[Transformer (Ferrite Core)]
davekni
January 18, 2021, 11:56:31 PM
post Re: how to run these guys?
[Transformer (Ferrite Core)]
Alberto
January 18, 2021, 11:50:22 PM
post Re: Segmented PTFE Secondary, Large Plasma Ball project
[Transformer (Ferrite Core)]
klugesmith
January 18, 2021, 10:30:15 PM
post Re: Segmented PTFE Secondary, Large Plasma Ball project
[Transformer (Ferrite Core)]
zytra
January 18, 2021, 10:03:46 PM
post Re: Segmented PTFE Secondary, Large Plasma Ball project
[Transformer (Ferrite Core)]
davekni
January 18, 2021, 09:58:44 PM
post Re: Segmented PTFE Secondary, Large Plasma Ball project
[Transformer (Ferrite Core)]
zytra
January 18, 2021, 08:52:29 PM
post Re: Segmented PTFE Secondary, Large Plasma Ball project
[Transformer (Ferrite Core)]
davekni
January 18, 2021, 07:08:09 PM
post Re: Adding interrupter Self oscillating tesla coil
[Beginners]
davekni
January 18, 2021, 06:49:28 PM
post Re: Alcatel Lucent B4 RRH2x60-4R teardown and reverse engineering
[Radio Frequency]
Da_Stier
January 18, 2021, 06:12:44 PM
post Re: Segmented PTFE Secondary, Large Plasma Ball project
[Transformer (Ferrite Core)]
klugesmith
January 18, 2021, 04:53:23 PM
post Adding interrupter Self oscillating tesla coil
[Beginners]
arto
January 18, 2021, 11:54:54 AM
post Re: Segmented PTFE Secondary, Plasma Ball project
[Transformer (Ferrite Core)]
zytra
January 18, 2021, 08:27:18 AM
post Re: Self Oscillating Half Bridge Wonder
[Solid State Tesla Coils (SSTC)]
Acid Byte
January 18, 2021, 06:57:06 AM
post Re: Segmented PTFE Secondary, Plasma Ball project
[Transformer (Ferrite Core)]
davekni
January 18, 2021, 06:43:19 AM
post Re: Segmented PTFE Secondary, Plasma Ball project
[Transformer (Ferrite Core)]
zytra
January 18, 2021, 05:48:27 AM
post Re: how to run these guys?
[Transformer (Ferrite Core)]
klugesmith
January 18, 2021, 01:03:48 AM
post Re: how to run these guys?
[Transformer (Ferrite Core)]
Alberto
January 18, 2021, 12:26:26 AM
post Re: how to run these guys?
[Transformer (Ferrite Core)]
davekni
January 17, 2021, 11:29:04 PM
post Re: how to run these guys?
[Transformer (Ferrite Core)]
Alberto
January 17, 2021, 09:55:24 PM
post Re: Segmented PTFE Secondary, Plasma Ball project
[Transformer (Ferrite Core)]
zytra
January 17, 2021, 09:34:21 PM
post Re: Segmented PTFE Secondary, Plasma Ball project
[Transformer (Ferrite Core)]
davekni
January 17, 2021, 08:51:50 PM
post Re: how to run these guys?
[Transformer (Ferrite Core)]
davekni
January 17, 2021, 08:04:54 PM
post Re: compact midi interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
tophat
January 17, 2021, 05:40:59 PM
post Re: Schlieren images projected onto a wall (no camera)
[Light, Lasers and Optics]
Uspring
January 17, 2021, 05:12:45 PM
post Re: how to run these guys?
[Transformer (Ferrite Core)]
SteveN87
January 17, 2021, 02:20:09 PM

SimplePortal 2.3.6 © 2008-2014, SimplePortal