Dear Mr. NickParker (Electrical)(OP)14 Sep 22 08:54
".... We have a LV Switchgear which feeds the VFD via MCCB (all enclosed in the same LV Switchgear), the MCCB is rated for the available fault current in the LV Switchgear but the VFD is not?...I guess it is okay ".
1. Your installation is typical in any industry.
2. On cost reasons, (the VFD by itself) are NOT designed with [high short-circuit capacity]. Therefore, the manufacturers always recommend the appropriate/tested? short-circuit protective device to be placed ahead of each VFD; either (a)* semi-conductor fuse (200kA), or (b)** Current-limiting CB. The manufacturers know better and in most cases tested by independent lab with certification. Refrain from any other alternatives, for safety reasons.
3. The incoming ACB or the branch standard MCCB which is rated for the available fault currents in the LV switchgear but the VFD is not... would NOT protect the VFD.
4. For safety reasons, strongly recommend to use the OEM recommended/documented (a)* or (b)**
5. FYI: Attention!, on the market there are numerous fuses* with same curve, but may NOT be so for the breakers**.
Che Kuan Yau (Singapore)