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Using Two Cables For A Single Motor


AB2005

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Dear All

 

Any body has any experience about two different sizes of cables connected in a single circuit? For example, I require 4Core 240mm² cable which is no longer available in market. Now I want to lay two cables 185mm² and 50mm² for power input to a DC drive which we are available in our store. Is it ok?

"Don't assume any thing, always check/ask and clear yourself".

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Are you proposing running a 185 in parallel with a 50 to give a total of 235?

 

Best regards,

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Are you proposing running a 185 in parallel with a 50 to give a total of 235?

 

Best regards,

Hello Marke

 

Sorry for delaying. Actually I am busy in erection of a corrugator machine.

Yes, your judgment is right. I want to connect two cables and get the total of 235mm.

 

"Don't assume any thing, always check/ask and clear yourself".

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Hello AB2005

Yes, technically, you can run two different sized cables in parallel, but there may be issues with the local standards and codes, and there is also a major problem with the current sharing/distribution.

 

If you consider the two cables, each cable with have a value of resistance over it's length. The resistance is going to be a function of the cross sectional area assuming equal length and material.

The current distribution will be inversely proportional to the resistance (or cross sectional area) of the cables.

 

In your case, 185mm plus 50mm, 78.7% of the current will flow in the 185mm and 21.3% will flow in the 50mm cable.

If we assume that the rating of the 185mm is 350Amps then the current rating of the pair would be 444Amps.

The current in the 50mm cable is 94.7 Amps which would be OK.

 

So, as you can see, it is not a case of adding together the current ratings or each cable, you have to do some calculations to determine the current distribution and ensure that the current in each core is not exceeded.

 

Best regards,

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Thanks for replaying

The load connected at the cables is a 220kw DC motor which has a Thyrister drive for speed control. So the current would be limited and under the range of two cables 185+50mm.

 

"Don't assume any thing, always check/ask and clear yourself".

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