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.

 

[Liamsparks]

We'll all happily help you but firstly try and have a look around this foum using the search facility. It'll help you learn and you'll also get some self pride out of sourcing the information yourself.

If you fail to find anything i'll happily help.

 

[04gallsopp]

Done 1 + 2 now thanks . Just some help with 3,4 and 5 please .

 

[Electricalserv]

Rs? not familiar with that sorry!

 

[04gallsopp]

My bad R2 sorry .

 

[Electricalserv]

My bad R2 sorry .

Not to worry mate I thought I was missing something there!

 

[04gallsopp]

can you help with my questions 3-4-5.

 

[Knobhead]

Have you tried looking for the answers? All to often this site seems to be used as a homework cheat.
I’m sorry but you can’t have a team on call in your exams.

 

[Electricalserv]

3.

[FONT=Trebuchet MS, Arial, Helvetica]1) The most expensive protection device for home use[/FONT]

[FONT=Trebuchet MS, Arial, Helvetica]2) Slow tripping time due to aging [/FONT]

[FONT=Trebuchet MS, Arial, Helvetica]3) Surrounding temperature may affect the MCB[/FONT]

[FONT=Trebuchet MS, Arial, Helvetica] 4.

[FONT=Trebuchet MS, Arial, Helvetica]1) Shorter tripping time [/FONT]

[FONT=Trebuchet MS, Arial, Helvetica]2) Can be reused[/FONT]

[FONT=Trebuchet MS, Arial, Helvetica]3) Easy to reset [/FONT]

[FONT=Trebuchet MS, Arial, Helvetica]4) Has a switch that can isolate the equipment[/FONT]

[/FONT]

 

[04gallsopp]

Have you tried looking for the answers? All to often this site seems to be used as a homework cheat.
I’m sorry but you can’t have a team on call in your exams.

Im sorry i object to that comment .
1. Im asking now so when i do my exams i wont need you there as i already know that question.
2. As a spark yourself you should be willing to help others that fall at a hurdle . Once you were struggling on questions and asked sombody.

I already have looked for the answer . But due to my inexperience i don't quite understand the answer the book give's . So i ask a mature and well experienced electrician like yourself and others to help me with my answers .

Thank you .
George Allsopp

 

[04gallsopp]

question 3 anybody ?

 

[telectrix]

Q.3. x5, x10, x20. for types B,C,D respectively.

 

[Goody]

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.

R1 – resistance of a live conductor of a circuit from the source end to the supply end (sockets and so on)
R2 – resistance of CPC (earth conductor) of a circuit from the source end to the supply end (sockets and so on)

Advantages of MCB

1. Instant re-closing of the circuit after a fault has been cleared
2. Safety disconnect features for circuit isolation
3. It is reusable, hence very little maintenance and replacement costs
4. Lower power losses
5. Simplicity of mounting and wiring
6. Stable arc interruption

Disadvantage of MCB

1. More expensive than the fuse
2. Difficult to identify where the fault occurred (arcing is barely noticeable at the point of short circuit)
3. Large amount of energy “let through” (10 times that released by the fuse)

Not sure of your question 3, check page 76 & 77 on BRB.

Best of luck!

 

[brucelee]

R1 is the sum of resistance of the line conductor
R2 is the sum of resistance of the circuit protective conductor

 

[i=p/u]

isnt it type b mcb say 6A x 5= 30

230/30 = 7.6 ohms???????????????? does that need to be corrected