3 phase fuse choice

[trebor]

If a 3 phase circuit has a total load of 54A ie 18A per phase is the choice of a BS88 fuse from the 0.4 sec table 41. because its below 32A or the 5 secs table 41.4 because the total load is above 32A

 

[johnboy6083]

I'd go with 0.4 as it's 32a per phase before the 5 sec rule applies!

 

[yellowvanman]

If its supplying another DB then its 5 seconds no matter what the current, otherwise 0.4 for 32A or less, 5 secs for greater than 32A.

 

[Guest123]

IMO it will be classed as a 20A circuit so 0.4s disconnection will apply.

 

[trebor]

Thanks Lenny, another thing bothers me now, accepting its 18 amps per phase and going with table 41.2 is it not 0.2s for 400V or am I reading it wrong
con fused.com !

 

[Guest123]

Table 41.1 gives the max disconnection times based on Uo, voltage line to earth.

So column 2, with Uo greater than 120V but less than or equal to 230V - 0.4s.