Efficient Cable Calculation for Urgent Motor Circuit - Help Needed

In summary, the conversation discusses the motor and circuit data for a 0.37kW motor, including nominal current, voltage, cable length, ambient temperature, and maximum voltage drop percentage. It also mentions the Bahraini regulations and calculations made to determine the appropriate cable section. The speaker is seeking help in finalizing the calculation and verifying the choice of a 2.5mm cable for 20 different equipments with varying power. They are advised to review their training and seek the assistance of a local electrician familiar with the regulations.
  • #1
walidabid
1
0
Good afternonn,
these are the motor and circuit data:

Motor power: 0.37kW,
Nominal current: I= 0.8 A
voltage: 415 V,
cable length = 80m
ambiant temperature: 50°C
Maximum voltage drop percentage =415*4% =16.6V

According to the Bahraini Regulations:
- temprature factor= 0.89
- core factor (3core cable)= 0.7

This is the calculation I did:
- target current=I/(0.89*0.7)=1,29A ==> 1,5A
when I check the current rated table, the suitable cable section will be 1.5mm but our contractor us a 2.5mm cable (I must verify his choice and prove that it's correct and submit the calculation to our consultant at least tomorrow morning!)

According to the current rated table, we get:
for the cable section: 2.5mm ==> current rating= 33A and Voltage drop /amp/m= 16

but when I calculate the Voltage drop /amp/m for my circuit, I find:
mV= dV*1000/(target current *L)= 16.6V*1000/(1,5A*80m) = 138,33mV >16 (from the table)

Now, what I have to do?
I don,t know how to proceed and finalize the calculation!

I have to make the verification for 20 different equipments with power variying between 0.37 and 48A!
Would you please help me and show me how to continue with the remainder calculation?

Your help is extreamly needed, I'am really blocked.
Thank you

Walid ABID
 
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  • #2
Walid ... your persistance is impressive how many more forums have you posted on?

Like I've mentioned before key to starting a cable calc for an inductive load is knowing what device you are going to protect the cable with as it will have to be able to cope with the inrush of the motor, having said that this is a very small motor and reduces that concern.
Secondly, regulations vary and unless one is knowledgeable of the bahraini electrical Reg's its thus a hard question to answer, we would need a copy of the regions electrical regs to attain the values to be applied.

Third and final you haven't stated what your cable type is nor its installation method, you have just given us values that you provide, we cannot confirm these without knowing you haven't made a mistake.

I assume you must be qualified to be requested to do this, if so you will have done this in your training and i recommend you review your notes or college books.

I can only re-iterate what i said before in that you need to discuss this with a local electrician who has knowledge of local rules and regulation, your tolerances in calcs may be tighter or more liberal than our (UK)... Hope you can appreciate how arkward trying to answer you question is, had you been UK base or even EU then it would have been a quick reply and full explanation.
 
  • #3
If this calculation needs to be done to local codes, then we cannot help you here. Thread is closed.
 

FAQ: Efficient Cable Calculation for Urgent Motor Circuit - Help Needed

1. What is "Urgent Cable Calculation Help Needed"?

"Urgent Cable Calculation Help Needed" is a request for assistance with performing cable calculations, typically in a time-sensitive situation.

2. Why are cable calculations important?

Cable calculations are important because they ensure the safety and efficiency of electrical systems. These calculations help determine the appropriate size, type, and placement of cables to handle the electrical load and prevent hazards such as overheating or short circuits.

3. Who needs cable calculation help?

Anyone who is responsible for designing, installing, or maintaining electrical systems may need cable calculation help. This can include electricians, engineers, and contractors.

4. What information is needed for cable calculations?

The specific information needed for cable calculations may vary depending on the system and its requirements. However, some common data that is typically required includes the voltage, current, power supply, load type, and cable length.

5. Where can I get urgent cable calculation help?

You can seek urgent cable calculation help from a variety of sources such as online forums, professional organizations, or consulting firms. It is important to ensure that the source is reputable and qualified to provide accurate and reliable assistance.

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