So without using the spacer and just swapping the inner capacitor tab bolt to a hex head would there be enough clearance to get a a small spanner in there to tighten the bolt?
Those inductance calculations are tricky. With the varying material thickness (ring, IGBT internals, capacitor tab, capacitor internals) the figures vary quite a bit. But i did notice that the radius of the conductor had a huge effect on the result. Just a small increase in the radius caused a huge reduction in the overall inductance figure. So the large cross-sectional area of the copper ring should help reduce the inductance.
I believe the calculator assumes a round conductor which means it is difficult to enter high radius numbers without it complaining of invalid parameters. The copper rings will have a large cross-sectional area but low height. So the rectangle could have a height so low that if the conductor was round the opposite sides of the rectangle would touch but with a flattened conductor the low rectangle height is achievable.
I guesstimated many of the parameters.
But a 60mm by 25mm rectangle will be around the 10nH inductance if you can get the conductor radius up to around 12mm.
Because the IGBT connections would be slap bang in the middle between two capacitor tabs would the cross-sectional area of the two connections (one to each capacitor tabs) combine to lower the inductance? Or would the inductance combine to double the inductance?
I do know for sure that it is way too early in the morning for maths. I was so engrossed in creating my dodgy diagrams last night that i only left 4 hours for sleep before the alarm insisted i go to work.
I better put heaps of comments on the software i write today because it is sure to slightly crazy.
These sort of problems sound like just the thing that students would love their teacher to challenge them with.
