motor question

[a1pacino]

where the wiring of a motor is through flexible conduit connected to earthed trunking the earth connection to the motor

a - should be via the flexible conduit

b - should be by a separate cable within the flexible conduit

c - should be connected to a bolt on the motor

d - should be connected to the earth terminal

Does anyone know the answer to this ive had a look but havent found answer?

 

[Andy™]

B - flex conduit cannot be considered as an earth, so will need an additional earth taken through it

 

[a1pacino]

cheers andy that was quick!

 

[green-hornet]

cheers andy that was quick!

Yeah he is like a poised Cobra !!

 

[Andy™]

just so happens that the thread was near the top when i clicked 'new posts'

 

[a1pacino]

got 301 coming up i have admins questions and memorized them as well as most of the formulas,any different questions that i may be up against would be much appreciated i hear its got a lot on motors and they are not my favourite subject i also have the questions welsh wizard posted which were useful as well

 

[green-hornet]

where the wiring of a motor is through flexible conduit connected to earthed trunking the earth connection to the motora - should be via the flexible conduit

b - should be by a separate cable within the flexible conduit

c - should be connected to a bolt on the motor

d - should be connected to the earth terminal

Does anyone know the answer to this ive had a look but havent found answer?

Just a thought for anyone who have to answer from multiple choice questions.

The best way to find the answer if you do not know it off the top of your head and lets face it we are electricians not doctors is to eliminate the unlikely.

From the above example lets take each answer choice one by one.

A, should be via the flexible conduit.

If flexable conduit is used we can assume there is going to be a vibration problem with the use of the motor, the flexible conduit whilst able to take the normal strains of vibration has weak points along its length that can be damaged, or even seperated.

Not likely to be relied upon for safe earthing.

B, Should be seperate cable within the flexible conduit.

If the flexible conduit for the reasons stated could not be relied upon for safe earthing then a seperate cable within the conduit would be a good solution.

C, Should be connected to a bolt on the motor.

We have already established that there is some vibration associated with the motor, so a bolt is unlikely, also which bolt? not likely to be a single bolt on a motor that has an earth symbol on it.

D, should be connected to the earth terminal.

Now then, now then, every earth cable must be connected to the earth terminal. This is where reading the question comes to the fore!

Its not asking the obvious we all know it should be connected to the earth terminal every earth should! Its asking about the method of supply to the connection, otherwise why mention the flexible conduit, or the earthed trunking?

By eliminating the obvious I would in this instance say that the answer is

B

Unless you have some sad lecturer who says its

D

In which case tell him all earthing is to an earth terminal

 

[madeinengland]

i did my 301 at the beginning of the year. i didn't get that many motor questions so i think it's luck of the draw.i have to agree with the green hornet it's a multiple choice exam and 9 times out of 10 you could eliminate 2 of the answers just by common sence even if you have no idea of the actual answer. good luck though and seriously you'll be fine. i wasn't confident at all and ended up with a credit. google "swindon massive" and you'll find a revision website with questions and answers.

 

[SPECIAL LOCATION]

where the wiring of a motor is through flexible conduit connected to earthed trunking the earth connection to the motora - should be via the flexible conduit

b - should be by a separate cable within the flexible conduit

c - should be connected to a bolt on the motor

d - should be connected to the earth terminal

Does anyone know the answer to this ive had a look but havent found answer?

Hello a1pacino

In addition to the excellent answers given by the others guys..

If you are in open book exam and you do want to find the actual reference in Big red for this sort of question you need to suss out what is the question about?

i.e. the question its not about motors, it is about earthing arrangements, protective conductors and specifically flexible conduits.

(the motor is used just to illustrate a location where flexible conduit would realistically be used.)

So look in the index for things like 'Earthing' or 'Flexible'.

when you look for 'Flexible' immediately you get to:-

Page 374 of index which has....

"Flexible conduits, prohibited as protective conductors": referencing reg 543.2.1

Nail on the head as they say!

The actual reg 543.2.1 on page 131 lists various things that cannot be used as a protective conductor, such as Gas pipes, Oil pipes, Flexible conduits, or structures subject to mechanical stresses etc...

If you were looking the other way through the book from contents..

on page 3 you can see

Chapter 54 Earthing arrangements and protective conductors

Then at Chapter 54 page 125 you can see

543.2 Protective conductors

Then 543.2.1 is actually the first reg in section 543.2

not sure if that helps anyone.. but gives a typical example of how to SatNav your way through Big Red!

(always a bit easier when not in an exam of course...

But still not too hard if you are looking for the right thing)

 

[green-hornet]

Good point, shows how to logically look for the information in the regs book.

 

[SPECIAL LOCATION]

Good point, shows how to logically look for the information in the regs book.

Basically we've covered two key methods to suss out a question you are unsure about.

GH method 1] : Logical common sense elimination process based on the information provided.

SL method 2] : Identify the key words and follow the book index/contents structure.

oh nearly forgot...............

Method 3] : sod it and grab a few of these Guiness DrinkGuiness DrinkGuiness DrinkGuiness Drink

:coat :coat

 

[a1pacino]

thanks,this forum and its users are first class

 

[Doc Hudson]

thanks,this forum and its users are first class

Thank you for your encouragement a1pacino, we do like to think that all of our members are first class.

Doc H.

 

[ElecQ]

And also, one of the biggest failings of the typical male is...

...we don't read the question

For some genetic reason or other, we tend to skim questions looking for pertinent points which will identify an answer. The two problems with this are:

1) Questions like "Which is the MOST likely..."

2) Questions like "Which of the following DO NOT..."

These tend to see us ignore the highlighted point and go for what we think are the correct answers. Only a couple of days ago I sat with a student who struggles with exams going through questions, getting him to read and assimilate them and answer them correctly. He was getting 28/30 on all the mocks he took with me talking the questions to him yet when he was on his own it was straight back to skim reading and failing the exam.

Most of the time the student knows the answer but struggles to understand the question. Some good advice in this thread for all I think.