Hi everyone,
I’m working on an industrial setup where a 3-phase motor load is being added to an existing distribution panel. The incoming supply is 415V and the starting current is quite high during motor start-up. I’m unsure whether an MCB would be enough protection here, or if I should go with an MCCB instead.
Is there a specific rule of thumb or load condition where MCCB becomes the safer/better choice over MCB? Mainly trying to understand it from a fault current and tripping capability point of view. Any practical guidance or examples would be appreciated.

 

https://eshop.se.com/in/blog/post/5-differences-between-mcb-and-mccb.html

I would normally use a MCCB on any 3-phase motor circuit above a few HP. That way I can adjust the trip-point to detect fault conditions before the motor fried due a load incident. They are slower to trip from higher than normal startup currents that are very common when pumping chemicals.

 

choice depends many factors. you did not reveal any info other than voltage and that load is inductive (motor).
MCBs are only available for smaller current, MCCBs are available for much higher currents. in terms of fault current ratings, both are rather low. often only really low such as 5-10kA for MCB and 8-20kA for MCCB. which is why for large interrupting capacity one may have to use fuses (even smaller fuse types tend to be rated for fault currents 100-200kA). so you need to know what is feeding your circuit and - what is the available fault current.

 

a lot of plants where my designs ended up had 480VAC 3P system and available fault current is often something like 25kA, 67kA, 125kA. and same client would sometimes insist on particular style of overcurrent protection, such as 100A frame MCCB from company XYZ, and those are only good for say 8kA. so what do you do? go back to what you are trained to do and always check with field inspector if he is ok with your proposal...