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Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
RickR, yes connecting the rings electrically is a must! It's still on the todo list.
Dr. Spark I had a question for you. What do you use for your MMC parameters in Fatboy? I was particularly interested in the voltage rating of your MMC as it seems to have held up a long time at the power level you run at. Was just looking for a general comparison.
Also I'm doing my best to have it finished by WWT, if not you can be sure to see both of these coils at WWT 2012
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Dr. Spark wrote ...
I must say am a bit envious of your build however, as flat primary and phase compensation but think will keep the antique DRSSTC (FATBOY) and just start over on a new super design FATBOY 2 using Finn’s new phase controller. Kind of fun looking at old coils and reflecting where we were five years ago.
The MMC is a string of five times 14 banks. Have fans on both sides of MMC keeping them cool in Arizona summers. The area that will focus on FATBOY 2 is the bus between caps. There is a lot more RF than first designed for and get a bit of heating on the MMC bus @ 240vac in @ 185us duration. Have added a second bus over first but not a clean design. Get a big fat copper bus between banks as hard to go back and add more.
Great work guys, thanks for sharing!
Dr. Spark
Thanks every one for the complements, gives me more motivation to finish the thing
So DR Spark you use a 28KvDC bank? 14 x 2kv?
I am not looking to break any records with this coil. The goal of this coil is to have a supper reliably big DR that can reliably push out 10 or 11 feet. I'm looking foreword to seeing how well phase lead works out with CM600HA-24H at 40KHz it should be near perfect ZCS!
It would be way cool to see a FATBOY 2! There's nothing like running two very large DRSSTC at the same time.
Registered Member #205
Joined: Sat Feb 18 2006, 11:59AM
Location: Skørping, Denmark
Posts: 741
Goodchild wrote ...
Great work you are doing. I saw your photos on flickr, nice to see someone posting scope shots, keep doing that here as well. Looking forward to seeing your solution when it comes to driving those CM600 gates!
We plan to use some rather large gate drive transformers to drive the gates of the CM600s. We came to this solution because of it's simplicity compared to high side gate drive. Ive driven large bricks in the past (such as CM300s) with GDTs and with great success, so I figured why could it not be applied here?
I am certainly not suggesting it can't. Thumper is driven by gate transformers, and did 13+ feet doing so. Even a 4:1 stepdown design, on 2 inch OD cores. Somehow, I felt I didn't have the same fine controll over the turn on and off of the bricks, and had to use gate resistors to get there. To me, it was a step back from active gate drive, and that is why I am presently going back. Still, good luck with yours, as a super reliable 10-11 footer machine you can´t loose with that design.
A note about designing the MMC: Voltage across the MMC: Calculate impedance Z, of cap @ Fres. Then voltage across is ohms law @Ipeak. Example: Fres: 40kHz, Cpri. 1.5uF, Z=2.65ohm
Voltage across @1700Apeak: 4505Apeak
Steve Conner is the originator of this formula to estimate RMS current, a key parameter in MMC design, Irms = 0.5*Ipk*sqrt(Ton*BPS)
I have had good results using the CD 940C12W1P5K-F. I have used them for Museum OLTC running now for 5 years on end, and Thumper logging a more modest hours.
When I test the motor on the bench, I do so with only one of these caps, in series with suitable coil, and it begins to break down at 3500V, passing 1000Apeak! It is the voltage that kills them.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
If you wanted total isolation, you could pump corn oil through the primary, then into a car/van transmission radiator, the radiator would sit in a large mass of water...that would give you absolute confidence of zero electrolysis, and 100% isolation. but, maybe you dont need it.
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Finn Hammer wrote ...
Goodchild wrote ...
Great work you are doing. I saw your photos on flickr, nice to see someone posting scope shots, keep doing that here as well. Looking forward to seeing your solution when it comes to driving those CM600 gates!
We plan to use some rather large gate drive transformers to drive the gates of the CM600s. We came to this solution because of it's simplicity compared to high side gate drive. Ive driven large bricks in the past (such as CM300s) with GDTs and with great success, so I figured why could it not be applied here?
I am certainly not suggesting it can't. Thumper is driven by gate transformers, and did 13+ feet doing so. Even a 4:1 stepdown design, on 2 inch OD cores. Somehow, I felt I didn't have the same fine controll over the turn on and off of the bricks, and had to use gate resistors to get there. To me, it was a step back from active gate drive, and that is why I am presently going back. Still, good luck with yours, as a super reliable 10-11 footer machine you can´t loose with that design.
A note about designing the MMC: Voltage across the MMC: Calculate impedance Z, of cap @ Fres. Then voltage across is ohms law @Ipeak. Example: Fres: 40kHz, Cpri. 1.5uF, Z=2.65ohm
Voltage across @1700Apeak: 4505Apeak
Steve Conner is the originator of this formula to estimate RMS current, a key parameter in MMC design, Irms = 0.5*Ipk*sqrt(Ton*BPS)
I have had good results using the CD 940C12W1P5K-F. I have used them for Museum OLTC running now for 5 years on end, and Thumper logging a more modest hours.
When I test the motor on the bench, I do so with only one of these caps, in series with suitable coil, and it begins to break down at 3500V, passing 1000Apeak! It is the voltage that kills them.
Cheers, Finn Hammer
You know Finn one other option I looked into that would give individual control back to each brick would be to use 4 GDTs one for each brick similar to how DR Spark dose it on FATBOY. In that way you could drive each GDT differently giving each brick it's own dead time phase shift ect... This way you would keep isolation and do away with all the extra isolated PSU circuity.
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10KVA DRSSTC (Complete)
