Time curves for bs 3871 devices

[silver surfer]

Apologies if this question has been done to death elsewhere.
Where would i find the time/current curves for BS3871 MCBs?
BS7671 only illustrates graphs for fuses and bs en 60898 and 61009 devices
I am trying to find out how long a 45 amp bs3871 mcb will withstand about 50-55 amps for on start up of discharge lighting.

cheers

 

[malcolmsanford]

View attachment Guide to CircuitBreaker standards.pdf

Try this SS

 

[MarkieSparkie]

Hi silver surfer, The time/current curves for BS3871 MCB's you're looking for are in 16th edition of the wiring regulations BS7671:1992 AMT 2, BYB, or earlier.

Time/Current Characteristics:
BS3781 40A Type 1 MCB, 0.1 to 5s = 160A
BS3781 40A Type 2 MCB, 0.1 to 5s = 280A
BS3781 50A Type 1 MCB, 0.1 to 5s = 200A
BS3781 50A Type 2 MCB, 0.1 to 5s = 350A

 

[scruffyspark]

Hi all, new here.

I'm trying to find the time curve for 1 type 2 3871 so I can get the T value for an adiabatic equation.

Can anyone help with this? Thanks in advance

 

[Richard Burns]

I have only ever found type 1 and 3.

Try using different values such as I²t or the tripping characteristics 4-7 times In.

(Welcome to the forum)