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Do I need to use semiconductor fusing?

Unconditionally, yes. This is the only way to protect the drive bridge in the event of a fault anywhere in the system, and it is a warranty condition for the drive. There are certain breaker types on the market that are claimed to be fast enough for semiconductor protection but we have yet to find one that affords the same protection as a correctly rated fuse.

Whilst on the subject it is worth pointing out that the maximum current rating of a fuse is of secondary importance as long as it is large enough - the drive current limit and stall algorithms are sophisticated enough to protect against damage by long term overload. The important part of the fuse rating is its I²T rating. Expressed in A²S (amps squared seconds) this is a measure of energy let through and the maximum allowable for any drive is given in the product manual fuse rating table. Essentially, if an I²T rating is not given in a manufacturers fuse specification details it is unlikely to be adequate - even if an alternative name such as "superfast" is used in the manufacturers description.

The above comments apply to fusing in the a.c. supply and the d.c. output to the armature, where a d.c. fuse is fitted. A.c. supply fusing is mandatory in all cases, d.c. fusing must also be employed in systems capable of regenerative current. With regard to the d.c. fuse, particular care should be taken to ensure that it is d.c. rated - the fuses used in the a.c. supply may not be, even if their I²T rating is correct.


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