AC Impedance Lower than AC Resistance 1

• May 13, 2020

1
• #2

7anoter4

Electrical

Oct 5, 2007

2,858

Effective Z is defined as R cos(θ) + X sin(θ).[ From voltage drop [approximate] formula: DV=length*effective Z ]
Then if X=0.058 ohm/1000ft and R=3.1 for pf=0.85 Zeff=3.1*0.85+0.058*sqrt(1-0.85^2)=2.67 ohm/1000 ft [r and Z are two separate definitions]

 

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• May 14, 2020

• Thread starter
• #3

Mbrooke

Electrical

Nov 12, 2012

2,546

I get they are separate values, however I've always assumed that if you added resistance and reactance together you get a higher impedance. I can't figure out why reactance would cause AC resistance to fall.

 

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• May 14, 2020

• #4

waross

Electrical

Jan 7, 2006

26,826

Can you give us a link to the origin of the table that you posted?
Thanks.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

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• May 14, 2020

• #5

7anoter4

Electrical

Oct 5, 2007

2,858

NEC 2017 Table 9 Alternating-Current Resistance and Reactance for 600-Volt Cables, 3-Phase, 60 Hz, 75°C (167°F) — Three Single Conductors

 

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• May 14, 2020

• #6

7anoter4

Electrical

Oct 5, 2007

2,858

 

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