400 hz fault current calculations

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garciasr77

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When calculating short circuit current for 400 vs. 60 cycle,
is it correct to estimate an increase in impedance by a factor of 7 plus a 10% margin?
 
bob

bob

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Location
Alabama
garciasr77 said:
When calculating short circuit current for 400 vs. 60 cycle,
is it correct to estimate an increase in impedance by a factor of 7 plus a 10% margin?
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It would depend on the length of the circuit. The increase in R , due to skin factor, is not directly related to frequency. X is directly related by 2xPixFxL. If X is much larger that R then you might use the your factor of 7 and be close.
 
J

jim dungar

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Location
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PE (Retired) - Power Systems
bob said:
It would depend on the length of the circuit. The increase in R , due to skin factor, is not directly related to frequency. X is directly related by 2xPixFxL. If X is much larger that R then you might use the your factor of 7 and be close.
Click to expand...

Skin effect does increase the R as the frequency increases and so it may need to be considered at 400Hz.
 
bob

bob

Senior Member
Location
Alabama
jim dungar said:
Skin effect does increase the R as the frequency increases and so it may need to be considered at 400Hz.
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Jim
What I should have said is the resistance is not directly proportional to the frequency as is the reactance.
The R is directly related to the frequency.
 
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J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
bob said:
Jim
What I should have said is the resistance is not directly proportional to the frequency as is the reactance.
The R is directly related to the frequency.
Click to expand...

Boy, how many times I wish I could say what I mean the first time.;)
 
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