Calculating Inductance

[krummelt1]

Hello Everyone

I am getting ready to take the October Exam and although this is something I am accomplishing at work it seemed to fall right in line with my studying.

I am trying to find the inductance of a wound coil. I have the following data

Applying 120VAC @60hz, the coil draws .87 Amps. The DC resistance is 2.84 ohms.

I modeled the coil as a known resistor in series with an unknown inductor.

I worked the problem as follows:

Calculated VA by multiplying V*I (104.4 VA)

Calculated W by (I^2)*R (2.14)

Using a power triangle calculated VAR (104.38 VAR)

Calculated X using VAR=(I^2)*X (137.93)

Solved for Inductance using 2*pi*f*L = X (.365H)

A co worker does not agree with my method, stating that I had ignored the current angle at the resistor. It made me question my method slightly but I THINK it is solid. What do you guys think do I have a flaw in my method?

TK

 

[cupojoe PE PMP]

I would need to spend more time thinking about this, this feels overly simplistic though. Should be easy enough to google for tutorials on solving RL series circuits.

 

[vangjer]

I would do:

Z = V/I = 137.9 Ohms

X = Sqrt(Z^2 - R^2) = 137.9 Ohms

L = X/(2*pi*f) = 0.366 H

Same answer.