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Size of protective conductor

Size of protective conductor

Vidar Grotle
Vidar Grotle

Hi

We have a cable 3x646AWG+3x4AWG. The line conductor is approximately 330 mm2 and the protective conductors are approximately 3x21,1mm2=63,3mm2.

According to IEC 60364-5-54 table 54.2 the protective conductors have to be half the size of the line conductor multiplied with a constant a: S*a/2. Is there any other rules or regulations to consider?

Can you say something about this constant a for this cable? Can we use this cable? Is the size of the protective conductors big enough? 

Can this cable be used to supply a VFD controlled AC motor? Rated Voltage: 587 V, rated current: 1120 A.

Re: Size of protective conductor

Re: Size of protective conductor

In Norway NEK 400 is the relevant standard. Sizing protective conductors shall follow Table 54B in NEK 400:2018. The small letter a is not a constant, just a given remark. Given your description the protective conductors seems too small.

The exact use of this cable is up to the producers assembly instructions.

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