BS 1361 50A ZS

[haptism]

Anyone know the ZS for an 1361 or BS 88-3 50A fuse. All the tables I find have n/a. I phoned the maker and was told there are no listed ZS' for a 50A and to take the difference between the next closest sizes (45A & 60), surley thats not proportional ?

 

[telectrix]

work it out. if the current required to blow the fuse in the required time is, say, 5In, then max. Zs = V/ 5In.

 

[haptism]

work it out. if the current required to blow the fuse in the required time is, say, 5In, then max. Zs = V/ 5In.

Thanks I will do just that

 

[westward10]

Use the 5A value and divide it by 10.

 

[haptism]

So i need to find out the fusing factor (the ratio of the In to overcurrent to operate in 0.1 secs) of a bs88 -3.

I need this factor for the formula that telextric has mentioned, where do i get the fusing factor from ? So far all i can find are the factors for B, C, D type MCBs ? Its not 1.45 is it ? Thats for cable

 

[haptism]

Use the 5A value and divide it by 10.

Im on a roll now and want to calculate it now west; sorry mate but its just not got the satisfaction value just dividing by 10 !!

 

[telectrix]

why 0.1sec? generally, anything over 32A needs to blow in 5 secs. to comply with BS7671.

 

[haptism]

why 0.1sec? generally, anything over 32A needs to blow in 5 secs. to comply with BS7671.

The current required to blow the fuse in the required time (5 secs) but thought quicker the better but maybe not such a good idea as itll skew results, so yeah 5secs it is. I cannot find no graphs/tables in relation to 50A. Overcurrent needed to blow the fuse in 5 secs ive so far found out can be calculated if you get the fusing factor (which each type of fuse has), where do I find this do you know ??

 

[Wilko]

We could do lottery pick - easier than finding that football ...
My pick is 0.927 Ohms for 5 sec on BS882 50A, from 248A guesstimate.

 

[haptism]

We could do lottery pick - easier than finding that football ...
My pick is 0.927 Ohms for 5 sec on BS882 50A, from 248A guesstimate.

Not far out from BS88 2 tables which is 0.996 ohms at 100% !!

 

[Leesparkykent]

Don't forget Cmin

 

[haptism]

Don't forget Cmin

Zs = (U0 × Cmin) / Ia

U0 = Voltage
Cmin = 0.95
Ia is the current causing operation of the protective device within the specified time. Which is what I need, in this case for a 50A BS88-3 or 1361 ??

 

[Wilko]

Don't forget Cmin

Oops, forgot that ... my guess now drops to 0.881 Ohms