It is (I think) a bit complicated to explain, but if someone has the time and the patience, it would be much appreciated, in the books I have I can see partial answers and how to calculate things but it is not always clear and makes sense:
1)Fuse breaking time 0.4 sec and 5 sec, when would you use one or the other.
2)As far I understand the 0.4 sec and 5 sec is for overload, there is an other time factor which is used when calculating the protective conductor's size. finding Ip (thermal constrain), and with it the time factor from the graph can calculate the protective conductor. How do I find the time from the graph if for example using fuse BS 88-2, cartridge, 16A radial circuit, 20m cable, flat twin & Earth 2.5mm2, metod 3. assuming that the circuit Zs is 0.32 Ohm, the Ip will be about 720A, looking in the graph the the Ip value does not fit in the 16A range, so what should I do?
3) Zs for fuses and circuit Zs (Ze+R1+R2), what is the difference.
thanks, Albert
1)Fuse breaking time 0.4 sec and 5 sec, when would you use one or the other.
2)As far I understand the 0.4 sec and 5 sec is for overload, there is an other time factor which is used when calculating the protective conductor's size. finding Ip (thermal constrain), and with it the time factor from the graph can calculate the protective conductor. How do I find the time from the graph if for example using fuse BS 88-2, cartridge, 16A radial circuit, 20m cable, flat twin & Earth 2.5mm2, metod 3. assuming that the circuit Zs is 0.32 Ohm, the Ip will be about 720A, looking in the graph the the Ip value does not fit in the 16A range, so what should I do?
3) Zs for fuses and circuit Zs (Ze+R1+R2), what is the difference.
thanks, Albert