Using Steel Fasteners Near Tank Circuit Connections

[Benjamin Lockhart]

Just a quick question. Is it alright to use steel bolts to connect up the MMC and IGBTs for a large(CM300) DRSSTC as long as they're not directly in the path of current?

I'm wondering if they will get hot just from close proximity or in a lug terminal.

For example, will this be fine with a steel bolt and nut in the center?



Thanks, Benjamin

[davekni]

Just a quick question. Is it alright to use steel bolts to connect up the MMC and IGBTs for a large(CM300) DRSSTC as long as they're not directly in the path of current?

I'm wondering if they will get hot just from close proximity or in a lug terminal.

For example, will this be fine with a steel bolt and nut in the center?

Short answer:  I don't expect any issues, but I have limited experience here.

Same question applies to bolts connecting bus bars to IGBT bricks.  I haven't heard of any need for copper bolts there.  If anyone has, please share.

My DRSSTC uses small bolts to connect lugs on my primary coil leads to corresponding lugs on MMC.  Bolt connections hang in open air.  Haven't had any issues with that.  I spent some time thinking about this question from a theoretical perspective.  Resulted in only guesses as to current flow distribution through such a connection based on skin effect and geometry and resulting flux through bolt head.  Certainly much less flux than for a bolt near primary coil.

[Late]

In my limited experience i think it should be fine. I used steel bolts to bolt on the busbars to MMC on my DRSSTC and I haven't encountered any issues with those bolts heating or anything. My DRSSTC runs at 900amp peak primary current.