Author Topic: Bleed R's for MMC caps ?  (Read 6425 times)

Offline pentode

  • High Voltage Enthusiast
  • *
  • Posts: 36
  • Karma: +2/-0
    • View Profile
    • humourous
Bleed R's for MMC caps ?
« on: February 21, 2019, 02:54:39 PM »
Looking at many MMC constructions on the net some have bleed R's across each cap but most
have none.

So, to bleed or not to bleed, that is the question?
 ..............Across caps rated at a few kV each!


 
« Last Edit: February 21, 2019, 02:56:12 PM by pentode »
"One small step for man"...
…..because he has Arthritis.
www.retinascope.co.uk

Offline Mads Barnkob

  • Administrator
  • Executive Board Member
  • *****
  • Posts: 2267
  • Karma: +71/-0
  • Denmark
    • View Profile
    • Kaizer Power Electronics
Re: Bleed R's for MMC caps ?
« Reply #1 on: February 21, 2019, 03:15:47 PM »
I seem to recall that it is a legacy from SGTC to balance out the MMC if the capacitance of the capacitors is not that great, something that has improved a lot with modern film power capacitors.

As to bleed off excess energy, for large DRSSTCs using a UD2.1 or higher version, a inverter bleeder resistor across the inverter output helps against instability issues due to energy residue in the MMC between pulses, so that kinds of removes the need for single capacitor bleeder resistors and the power rating / voltage rating is also much lower for a 10K power resistor across the inverter, compared to the usually used 10M metal film resistors on the single caps.

Any others have a comment on this?
https://kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics
https://www.youtube.com/KaizerPowerElectronicsDk60/join - Please consider supporting the forum, websites and youtube channel!

Offline Hydron

  • Administrator
  • High Voltage Engineer
  • *****
  • Posts: 487
  • Karma: +25/-0
    • View Profile
Re: Bleed R's for MMC caps ?
« Reply #2 on: February 21, 2019, 06:06:46 PM »
Individual bleed resistors would eliminate the danger of getting a zap off a MMC cap due to uneven stored charge, whereas across the bridge gives less guarantees. Not sure how much of an issue this is in reality though.

I would definitely recommend a resistor across the bridge as Mads said, especially if you are using a UD2.x style driver. Only needs to withstand the bus voltage at your max duty cycle so it's easy and cheap to add.

Offline pentode

  • High Voltage Enthusiast
  • *
  • Posts: 36
  • Karma: +2/-0
    • View Profile
    • humourous
Re: Bleed R's for MMC caps ?
« Reply #3 on: February 22, 2019, 08:28:17 AM »
Thanks both for that.
Incidentally Max,on your excellent article on MMC
http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/mmc-tank-capacitor/
you show photos of MMC caps both with and without individual bleeders.
I daresay many are photos going back some time though.
"One small step for man"...
…..because he has Arthritis.
www.retinascope.co.uk

Offline Hydron

  • Administrator
  • High Voltage Engineer
  • *****
  • Posts: 487
  • Karma: +25/-0
    • View Profile
Re: Bleed R's for MMC caps ?
« Reply #4 on: February 22, 2019, 10:07:23 AM »
Thinking about it more, I personally would add the bleed resistors if only for safety when working on the MMC/coil. It is unfortunately quite annoying to solder them all (I once put together a MMC with 512 bleed resistors - two in series for each cap!).

You will need to try and find resistors with a suitable "overload" voltage or put two in series - their normal rated voltage for steady state is often significantly lower than the MMC capacitor rating but we are not running them in steady state operation.

If you have PCB design experience then you could maybe get something made by a cheap chinese PCB supplier to hold the caps and bleed resistors - they are extremely cheap, especially if you only have 2 layers and 1oz copper, and you can always use both layers (and even stack a couple of identical boards) to get the amount of copper up. See https://github.com/Hydron-4hv/QCW_MMC_PCB/raw/master/Reference%20Outputs/Schematic%20%26%20BoM/QCW_MMC_PCBA-(NO_WE_PRESSFIT).PDF for one I did (I built up 8 of these boards!).

Finally I would not worry so much about the current sharing bit in Mad's guide - this is important for sharing between low impedance parts such as bus capacitors or semiconductors, but the impedance of the MMC capacitors is high enough that they should share pretty much perfectly regardless of connection point unless you do something wrong. Do however space the caps out a bit, and try not to have the resistors touching the caps too.

Offline pentode

  • High Voltage Enthusiast
  • *
  • Posts: 36
  • Karma: +2/-0
    • View Profile
    • humourous
Re: Bleed R's for MMC caps ?
« Reply #5 on: February 22, 2019, 12:20:26 PM »
512 resistors. Wow!
Unlike your huge array I only have 18  poly 942  caps to fit so it's easy to put them in
my small 6 x 3 array.

Does your M10.2 R's take a long time to discharge caps?
The bleed current will be very low, at 1000 v being only
some 100 micro amps !
I would wait some time before getting hold of them :)

Thanks for suggestions though.
« Last Edit: February 22, 2019, 12:24:34 PM by pentode »
"One small step for man"...
…..because he has Arthritis.
www.retinascope.co.uk

Offline Hydron

  • Administrator
  • High Voltage Engineer
  • *****
  • Posts: 487
  • Karma: +25/-0
    • View Profile
Re: Bleed R's for MMC caps ?
« Reply #6 on: February 22, 2019, 04:34:14 PM »
Actually it's very quick to discharge - the caps are only 6.2nF so the time constant is only 63ms - enough to render the array safe in well under a second, and even enough to perform the job of the inverter bleed resistor too given the low pulse rep rate of the QCW coil this MMC has been built for. From a safety perspective a 10M resistor should be good enough for even capacitors into the low-uF range if you give them a minute or two to discharge.

For 18 caps I would 100% put them in, even if you have to put two in series 36 resistors will not take long to solder up.

Offline pentode

  • High Voltage Enthusiast
  • *
  • Posts: 36
  • Karma: +2/-0
    • View Profile
    • humourous
Re: Bleed R's for MMC caps ?
« Reply #7 on: February 23, 2019, 08:36:58 AM »
Ooops sorry, I read your nano caps as Micro farads !

Whilst on bleeders I have a 6,800 microfarad filter cap  working at 360 volts
to bleed.
Using  8k still leaves 40v after 2 minutes !
"One small step for man"...
…..because he has Arthritis.
www.retinascope.co.uk

Offline Hydron

  • Administrator
  • High Voltage Engineer
  • *****
  • Posts: 487
  • Karma: +25/-0
    • View Profile
Re: Bleed R's for MMC caps ?
« Reply #8 on: February 23, 2019, 03:04:49 PM »
Yes I know about that well - I have 4x6800uF for my qcw coil and an even larger bleed resistor - takes a long time to drop to a safe level. I do however have a high efficiency led in series with the bleeder R to tell me when there is voltage present - stays obviously lit until well after its safe. May also add a neon indicator to be doubly sure.

Offline pentode

  • High Voltage Enthusiast
  • *
  • Posts: 36
  • Karma: +2/-0
    • View Profile
    • humourous
Re: Bleed R's for MMC caps ?
« Reply #9 on: February 23, 2019, 03:38:09 PM »
 FOUR 6800's. Gosh :)

That's a nice idea. I may put one on my 6800.
Better safe than sorry.
But putting something in series with bleeders puts
  a lot of faith in their continuity, don't you think? .  ;D


« Last Edit: February 23, 2019, 03:42:09 PM by pentode »
"One small step for man"...
…..because he has Arthritis.
www.retinascope.co.uk

Offline Hydron

  • Administrator
  • High Voltage Engineer
  • *****
  • Posts: 487
  • Karma: +25/-0
    • View Profile
Re: Bleed R's for MMC caps ?
« Reply #10 on: February 24, 2019, 12:25:05 AM »
yeah that did occur to me - hence the planned addition of a neon indicator (which should run on DC OK) as a separate safety feature.

So far I have only had it running up to ~100V in testing, though I did manage to short it out at ~50V or so with a test probe (which promptly disappeared into vapour!).

I'd rather not run so much capacitance, but for a QCW I need to have enough to avoid the bus voltage drooping too much over a single pulse and a thumping great capacitor bank was the easiest (and cheapest, given I got them free) way to do it.

High Voltage Forum

Re: Bleed R's for MMC caps ?
« Reply #10 on: February 24, 2019, 12:25:05 AM »

 


* Recent Topics and Posts

post Re: Big Coil Build Log
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
Today at 05:47:34 AM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
davekni
Today at 04:45:07 AM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
MRMILSTAR
Today at 04:18:27 AM
post Push Pull VTTC
[Vacuum Tube Tesla Coils (VTTC)]
janno288
Today at 01:10:08 AM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
Alberto
March 27, 2024, 10:54:52 PM
post Re: CM400 Induction Heater
[Electronic Circuits]
markus
March 27, 2024, 11:53:42 AM
post Re: OCD Triggering Early + Low Output
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 27, 2024, 05:14:36 AM
post Re: Is the UD2.7C under voltage lock out basically worthless?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 27, 2024, 04:47:48 AM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 27, 2024, 04:41:59 AM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
March 27, 2024, 12:04:34 AM
post Re: Super flat QCW simulation (does this look reasonable?)
[Dual Resonant Solid State Tesla coils (DRSSTC)]
toooldforthis
March 26, 2024, 11:08:14 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 26, 2024, 11:07:20 PM
post Re: Is the UD2.7C under voltage lock out basically worthless?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 26, 2024, 10:46:29 PM
post OCD Triggering Early + Low Output
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Saattvik24
March 26, 2024, 09:03:43 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
March 26, 2024, 08:46:59 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 26, 2024, 05:02:18 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
March 26, 2024, 03:16:03 PM
post Re: CM400 Induction Heater
[Electronic Circuits]
Anders Mikkelsen
March 26, 2024, 01:41:49 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 26, 2024, 04:48:22 AM
post Re: Re-chargeable 1.5 volt lithium ion AAA batteries
[General Chat]
MRMILSTAR
March 26, 2024, 04:16:37 AM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 26, 2024, 04:16:24 AM
post Re: Smoke Screen Machine Protect 950 XP - Teardown of a Smoke Cannon!
[Electronic Circuits]
davekni
March 26, 2024, 04:13:02 AM
post Re: CM400 Induction Heater
[Electronic Circuits]
davekni
March 26, 2024, 04:00:43 AM
post Re: Re-chargeable 1.5 volt lithium ion AAA batteries
[General Chat]
davekni
March 26, 2024, 03:19:18 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
thedoc298
March 26, 2024, 01:50:42 AM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 25, 2024, 08:05:02 PM
post Re: Smoke Screen Machine Protect 950 XP - Teardown of a Smoke Cannon!
[Electronic Circuits]
Mads Barnkob
March 25, 2024, 07:41:29 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
March 25, 2024, 06:45:46 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 25, 2024, 05:44:25 PM
post Re: CM400 Induction Heater
[Electronic Circuits]
Anders Mikkelsen
March 25, 2024, 04:47:17 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
March 25, 2024, 04:27:22 PM
post Re-chargeable 1.5 volt lithium ion AAA batteries
[General Chat]
MRMILSTAR
March 25, 2024, 03:57:34 PM
post Re: CM400 Induction Heater
[Electronic Circuits]
markus
March 25, 2024, 02:06:41 PM
post Re: Odd MOSFET Driver Behavior
[Solid State Tesla Coils (SSTC)]
KrisPringle
March 25, 2024, 04:43:25 AM
post Re: Odd MOSFET Driver Behavior
[Solid State Tesla Coils (SSTC)]
davekni
March 25, 2024, 02:39:40 AM
post Re: Odd MOSFET Driver Behavior
[Solid State Tesla Coils (SSTC)]
KrisPringle
March 25, 2024, 12:47:09 AM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
Alberto
March 24, 2024, 07:36:32 PM
post Re: My completed 14-stage Cockroft-Walton voltage multiplier
[Voltage Multipliers]
Alberto
March 24, 2024, 07:27:24 PM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
MRMILSTAR
March 24, 2024, 04:25:23 AM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
Alberto
March 23, 2024, 10:47:35 PM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
MRMILSTAR
March 23, 2024, 09:30:21 PM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
Alberto
March 23, 2024, 04:34:31 PM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
MRMILSTAR
March 23, 2024, 03:04:25 PM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
Alberto
March 23, 2024, 01:38:34 PM
post Re: capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
MRMILSTAR
March 23, 2024, 04:20:03 AM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
davekni
March 23, 2024, 12:54:30 AM
post Re: Smoke Screen Machine Protect 950 XP - Teardown of a Smoke Cannon!
[Electronic Circuits]
davekni
March 23, 2024, 12:05:57 AM
post capacitor and diodes. Voltage values for a CW
[Voltage Multipliers]
Alberto
March 22, 2024, 11:45:03 PM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
OmGigaTron
March 22, 2024, 11:30:09 PM
post Smoke Screen Machine Protect 950 XP - Teardown of a Smoke Cannon!
[Electronic Circuits]
Mads Barnkob
March 22, 2024, 10:20:35 PM
post Re: Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
Benbmw
March 22, 2024, 09:21:13 PM
post Re: What actually kills MOSFETs?
[Beginners]
AstRii
March 22, 2024, 03:37:11 PM
post What actually kills MOSFETs?
[Beginners]
FPS
March 22, 2024, 05:09:20 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 22, 2024, 03:57:54 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 22, 2024, 02:59:25 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 21, 2024, 06:31:42 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
rikkitikkitavi
March 21, 2024, 03:08:01 PM
post Re: [WTS] IGBT, Ferrite, Capacitors, Tools, PSU, Industrial components and parts
[Sell / Buy / Trade]
Mads Barnkob
March 21, 2024, 01:37:32 PM
post Re: Difference between these transformers
[Transformer (Ferrite Core)]
Alberto
March 21, 2024, 11:42:07 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 21, 2024, 04:09:14 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 21, 2024, 02:15:31 AM
post My Homemade Structural Analysis X-Ray Machine
[X-ray]
Luca c.
March 21, 2024, 01:35:40 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Saattvik24
March 20, 2024, 10:40:00 PM
post Re: Difference between these transformers
[Transformer (Ferrite Core)]
Mads Barnkob
March 20, 2024, 08:03:41 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Mads Barnkob
March 20, 2024, 07:51:57 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
March 20, 2024, 10:39:47 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 20, 2024, 04:09:59 AM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 20, 2024, 01:13:23 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Keybored
March 20, 2024, 12:45:16 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 20, 2024, 12:30:30 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 19, 2024, 11:12:24 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 19, 2024, 09:47:49 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 19, 2024, 09:44:19 PM
post Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Saattvik24
March 19, 2024, 06:52:09 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 19, 2024, 05:02:44 PM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
Mads Barnkob
March 19, 2024, 05:01:41 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
March 19, 2024, 04:31:02 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
March 19, 2024, 03:59:54 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 19, 2024, 06:41:39 AM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
davekni
March 19, 2024, 04:05:49 AM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
OmGigaTron
March 18, 2024, 09:08:35 PM
post Re: Can I Trust This Super Cheap Site?
[General Chat]
2020-Man
March 18, 2024, 09:07:35 PM
post Re: Can I Trust This Super Cheap Site?
[General Chat]
Twospoons
March 18, 2024, 08:57:06 PM
post Re: Can I Trust This Super Cheap Site?
[General Chat]
MRMILSTAR
March 18, 2024, 03:51:33 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 18, 2024, 02:59:46 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 18, 2024, 02:33:25 PM
post Can I Trust This Super Cheap Site?
[General Chat]
2020-Man
March 18, 2024, 11:02:12 AM
post Re: Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
Twospoons
March 18, 2024, 02:36:11 AM
post Re: Best forum for vacuum tube amplifiers?
[General Chat]
Mads Barnkob
March 17, 2024, 07:42:55 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Michelle_
March 17, 2024, 04:15:14 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Michelle_
March 17, 2024, 05:05:04 AM
post Re: Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
davekni
March 17, 2024, 04:50:51 AM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Twospoons
March 17, 2024, 04:45:17 AM
post 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Michelle_
March 17, 2024, 04:17:51 AM
post Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
Terry
March 17, 2024, 01:29:32 AM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 17, 2024, 12:33:06 AM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Keybored
March 16, 2024, 08:46:20 PM
post Re: Bleeder resistor for MMC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Hydron
March 16, 2024, 08:39:24 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Hydron
March 16, 2024, 08:21:44 PM
post Best forum for vacuum tube amplifiers?
[General Chat]
yourboi
March 16, 2024, 08:20:13 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