Im an apprentice in need of desperate help.

[04gallsopp]

Im an apprentice as you've all been . An our lecturer has given us the usual homework and im stuck on some questions . Please help.
1. Define R1
2. Define Rs
3. The multiple used to show the prospective fault current required to trip an MCB for Type B,C,D
4. 3 Disadvantage's of an MCB
5. 3 Advantage's of and MCB

Thanks for your time in helping me get on with my questions ha ha.

 

[wurm]

ouch ... lolz

 

[04gallsopp]

Got it

A 6 A Type B MCB to BS En 60898 which is used to protect a domestic lighting circuit will trip within 0.4s when 6A times a multiple of 5, that is 30A flows under fault condition.

Therefore if the earth fault loop impedence is low enough to allow at least 30A to flow in the circuit under fault conditions , the protective device will operate within the time required by the Regulation 411

Type B MCB to BSEN60898 Has a Multiple of 5

Type c MCB to BSEN60898 Has a Multiple of 10

Type D MCB to BSEN60898 Has a Multiple of 20

This takes into acount Discrimination.