Type D MCB 5 Second Tripping Current

Former Community Member over 4 years ago

In BS 7671 17th Edition A3 table 41.3 for type D MCBs gives a 5 second tripping current as 230 x 0.95 / (10In).

When cross referencing time current graphs for type D MCBs I do not get a value of 10In for a 5 second tripping time.

For example see ABB time current graph below giving a current of around 16In for a 5 second trip time.

What is the reason for the difference in values when comparing type D MCB time current charts and table 41.3 in BS 7671 17th Edition A3 for 5 second trip times?

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0 Former Community Member over 4 years ago

I'd go along with that - with sensible margins adopted, it would be a foolproof method of showing compliance with 0.4 and 5 second disconnections, based on data already required in BS EN 60898-1 - but we have something very similar with limiting Zs values so it may well not warrant the change of approach

Regards

OMS
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0 Former Community Member over 4 years ago

I'd go along with that - with sensible margins adopted, it would be a foolproof method of showing compliance with 0.4 and 5 second disconnections, based on data already required in BS EN 60898-1 - but we have something very similar with limiting Zs values so it may well not warrant the change of approach

Regards

OMS
Cancel
Vote Up 0 Vote Down

Cancel

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Type D MCB 5 Second Tripping Current

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