Buss Bar Forces, Distribution Chassis, Short Circuit Testing

[BigMax]

Hi all.

 

Apologies if I'm posting this in the wrong area of the forum, but......

 

I'm currently involved in the development of a 400VAC 50Hz 3phase +N 1600A MCCB chassis. This chassis is double ended, as such, amongst many design requirements, we need to succesfully pass a 63kA thru current short circuit test.

 

Whilst I'm reasonable confidant I understand the level of force produced between the bars (horizontal, with the chassis lying down), actual tests seem to indicate a vertical force which is upsetting the applecart.....bending the bars upwards and breaking our bussbar support system.

 

This vertical force may be the result of the bars twisting out of the intermediate supports we have developed......or it may be the result of interaction between the bussbars and the mild steel chassis pan located approximately 1 phase spacing distance below.

 

So far I have found no reference to such an interaction, though I can imagine it does exist. What I don't know is how to estimate the effect or if it can be simply ignored.

 

Any comments or suggestions will be most welcome.

 

Cheers!

 

BigMax

[RalphChristie]

BigMax

 

Most probably way to late, but I saw this post only today...

 

For anyone interrested in short-circuit effects on busbars check:

http://www.cda.org.uk/megab2/elecapps/pub22/sec6.htm

http://www.cda.org.uk/megab2/elecapps/pub22/sec8.htm

 

Regards

[BigMax]

RalphChristie,

 

The late reply is no problem, an answer to my question was a bit of a longshot anyway.

 

It seems that, to an extent, the answer to my question is a key (secret?) ingredient in the recipe for compact high current chassis design ;f;

 

I (and the team I work with) have learn't a lot since I posed the question. The vertical interaction force do seemingly exist but are of much lesser magnitude than the horizontal forces between bars.

 

So, our solution was to create an overengineered design from the point of view of the horizontal forces which was not impractically expensive. Our design then passed a 63kA 1 second through current test with zero bar distortion or support damage.

 

Very satisfying.

 

PS, we choose to maintain the secret force ingrediant:P

 

Cheers!

 

Big Max