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Austin

Sun Jan 27 2008, 03:33AM

Registered Member #1169 Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251

I have to order more of those CR's cause the book said I needed 11 when in reality I needed 12.

Wirenut

Sun Jan 27 2008, 04:01AM

Registered Member #141 Joined: Sat Feb 11 2006, 01:14PM
Location: Southern California
Posts: 96

As long as you're ordering parts, you might want to order some of the 220V TVSs, I seemed to go through a lot of them before I got it sorted out, and they're relatively cheap. Also, it couldn't hurt to have some spare gate drivers on hand. And you do have some spare IGBTs, right?

Austin

Sun Jan 27 2008, 05:18AM

Registered Member #1169 Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251

so expensive for those IGBTS.... i need extras? :(

Wirenut

Sun Jan 27 2008, 06:11AM

Registered Member #141 Joined: Sat Feb 11 2006, 01:14PM
Location: Southern California
Posts: 96

so expensive for those IGBTS

There's been some talk about using hgtg20n60a4d instead. They are TO-247 form factor so they do not dissipate heat as well as the hgt1n40n60a4d which are sot-227 package, but other than that they should work, and they're much cheaper at only $5 or so each. I recently purchased some, and I'm going to try them out, and I'll report back on how they work. Of course, the miniBrute half-bridge board was not made for these IGBTs so some modifications will be necessary, but I have a spare half-bridge board to play with.

i need extras? :(

Maybe learning from my (and others) mistakes will save you from blowing IGBTs, but if you ask most people on this forum who have built DRSSTCs, I think they will tell you that they've blown at least a few, and having at least 1 spare set is a good idea. I'd rather have a spare set and never need them than blow a couple and have to wait a week or so to fix it. But that's just me, $70 for spares that *might* not be needed is a lot.

HV Enthusiast

Sun Jan 27 2008, 03:03PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

if you keep the current limit way down low for the initial testing, you can drastically increase reliability of the IGBTs. And yes, the TO-247 package IGBTs work great. Just make sure you mount them to a good heatsink and properly with thermal grease etc...
Also, they need to be electrically insulated as well.

Regarding tuning of the potentiometers, you are merely setting the current limit here (table on schematic shows what the values are - start low), and i believe some others for setting the LEDs on the current meter which is non-functional anyways other than the display.

Just be sure to get a good understanding of HOW the circuits work. They are VERY simple (just simple comparators, digital logic, etc...) and once you understand them, than setting the values within each circuit is very simple.

Austin

Mon Jan 28 2008, 02:52AM

Registered Member #1169 Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251

since I don't see a heat sink on the parts list for the IGBT's what kind did you use Wirenut?

Wirenut

Mon Jan 28 2008, 03:04AM

Registered Member #141 Joined: Sat Feb 11 2006, 01:14PM
Location: Southern California
Posts: 96

since I don't see a heat sink on the parts list for the IGBT's what kind did you use Wirenut?

I bought mine from this guy on ebay

He'll cut it to any length you want (I had him cut a 4" and an 8") and the cuts are perfectly smooth. The heatsink is very beefy and probably overkill, but his price is fantastic, and he ships quickly in very good packaging. I mounted my bridge on the 4" section - fits very well.

Austin

Mon Jan 28 2008, 03:22AM

Registered Member #1169 Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251

4" x 8" correct? and how did you mount it? Did you drill some holes in the heatsink and screw it to the base? also the part list does not call for any screws, or screw mounts to attach the boards to the inside frame. any recommendations.

Wirenut

Mon Jan 28 2008, 03:54AM

Registered Member #141 Joined: Sat Feb 11 2006, 01:14PM
Location: Southern California
Posts: 96

4" x 8" correct?

Actually it's 4" x 5 and 3/8". The heatsink is 5 and 3/8" wide and he sells it by the foot, but he'll cut the foot into any smaller lengths you want like 6"+6" or 8"+4" (like I did).

and how did you mount it? Did you drill some holes in the heatsink and screw it to the base?

It's attached to the rear wall with two countersunk screws from the outside going through two of the fins.

any screws, or screw mounts to attach the boards to the inside frame. any recommendations.

As far as mounting goes, the most difficult part was mounting the IGBTs to the heatsink. You can use the half-bridge board as a stencil for the mounting holes. As far as the boards go, I had tons of assorted hardware laying around, and I just used whatever worked. Home Depot and the like have assorted hardware. Also, I think that you should mount the main resonant board in a vertical position to minimize interference from the primary coil. I mounted mine to a slightly larger (than the resonant board) piece of polycarbonate and mounted the polycarbonate using cheap angle brackets from H.D.

Austin

Mon Jan 28 2008, 04:00AM

Registered Member #1169 Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251

Thanks again for the tip. I get most of my PVC in tomorrow so hopefully I'll start construction Monday or Tuesday. Until then theres not much I can do considering I am waiting on parts.

I really hope someone else stumbles upon this post like a month or two down the road and finds this information as valuable as I have.

Oh and one more comment about C81, I found out after reading the book a bit more in detail that it is in fact mentioned in the book (on a side note) and should be soldered in parallel with the U81 sensor. "C81 should be placed as close to U81 as possible directly across the lead of the device." Thought this was worth mentioning.

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