Voltage Drop

[akmal]

Hi,

I am sitting in C & G 94/95 exams on 22/04/2015. i am attempting past papers and got confused regarding some voltage drop questions below:
1.Compliance with the voltage drop for a 230 v single-phase electric Kiln circuit is to be confirmed. The circuit is installed using thermoplastic 70 selcious insulated SWA cable, in a craft workshop.

a) State three reasons why voltage drop cannot determined using voltage drop measurement at both the origin and the furthest point on the kiln circuit.
b) The length of the circuit cannot be measured. State the method to be used to confirm the voltage dropto the kiln is within the permitted limits given in BS 7671.

C) State four factors that have a direct effect on voltage drop in a final circuit.


Please, can someone help at this stage. It will be appreciated.

Thanks

 

[alanl]

Write down what you think are the answers.
It is quite simple.
Think about what the voltage is at the incomer.
Presumably this is an industrial area - what happens to the voltage when a motor is turned on?
Length cannot be measured. But you can do a R1 and R2 measurements cant you?
And there are tables available telling you what the resistance of the conductor is - have a think about it.
4 factors on VD - this is simple, think about it again.

 

[GB.Kayak]

Write down what you think are the answers.It is quite simple.Think about what the voltgae is at the incomer. Presumably this is an industrial area - what happens to the voltage when a motor is turned on?Length cannot be measured. But you can do a R1 and R2 measurements cant you? And there are tables available telling you what the resistance of the conductor is - have a think about it.4 factors on VD - this is simple, think about it again.

... 'motor turned on' ... what motor?

 

[alanl]

For the simple minded, measure the voltage at a point near a DB.
Then measure it again when a motor is starting up.
Or any current sapping equipment.

What happens to the measured voltage?

 

[ian.settle1]

For the simple minded, measure the voltage at a point near a DB.
Then measure it again when a motor is starting up.
Or any current sapping equipment.

What happens to the measured voltage?

Hello for the second time of asking what MOTOR the OP hasn't mentioned one

 

[davesparks]

Hello for the second time of asking what MOTOR the OP hasn't mentioned one

If you read post 2 he is talking about what happens to the voltage when other equipment (including motors) in the workshop is used.

Why he specified motors instead of just saying other loads I couldn't say

 

[GB.Kayak]

If you read post 2 he is talking about what happens to the voltage when other equipment (including motors) in the workshop is used.

Why he specified motors instead of just saying other loads I couldn't say

The OP did not mention a motor; post 2, not from the OP, introduces the motor presumably as an example to examine what impacts voltage drop ...

 

[Knobhead]

A motor is a bad analogy, the inrush is only of a short duration and voltage drop at the motor terminals is acceptable.

 

[Richard Burns]

Hi,

I am sitting in C & G 94/95 exams on 22/04/2015. i am attempting past papers and got confused regarding some voltage drop questions below:
1.Compliance with the voltage drop for a 230 v single-phase electric Kiln circuit is to be confirmed. This is a design calcualtion see appendix 4 on volt drop. The circuit is installed using thermoplastic 70 selcious insulated SWA cable, in a craft workshop.

a) State three reasons why voltage drop cannot determined using voltage drop measurement at both the origin and the furthest point on the kiln circuit.
what is the reference voltage for volt drop, what current is being drawn, what may affect the measured voltage?
b) The length of the circuit cannot be measured. State the method to be used to confirm the voltage dropto the kiln is within the permitted limits given in BS 7671.
How would you calculate the length of a piece of cable (answer has been given in posts above)?

C) State four factors that have a direct effect on voltage drop in a final circuit.
Think about the formula for volt drop this will give you three factors immediately

Please, can someone help at this stage. It will be appreciated.

Thanks

Comments in red above