×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Simple execise to measure the ac current thru a coil!

Simple execise to measure the ac current thru a coil!

Simple execise to measure the ac current thru a coil!

(OP)
I’m doing a simple experiment to measure the ac current thru a coil and I’m getting nowhere close to the calculated values. The coil is hand wound and has a value of 57mH when measured by an LCR meter. It also has a resistance value of 2.61ohms measured by the same meter. My power supply is 13.08 volts at 50 hz. If I do the math I get a reactance value of 17.9 ohms. The total impedance for the circuit is therefore 18.1 ohms. Connected to my supply of 13.08v, the calculated current is 0.722A.
Now when I build the circuit I see a current of 0.24A! Does anyone know why the discrepancy? Could it have something to do with the impedance of the power supply?

Thanks

RE: Simple execise to measure the ac current thru a coil!

(OP)
It's ok I made a fundamental error. Measured the resistance of the coil wrongly, should be 50 ohms not 2 ohms.

RE: Simple execise to measure the ac current thru a coil!

That explains it all right. I was going to suggest another explanation IF your coil has soft magnetic core. The iron core is highly non-linear and that non-linearity is not significant just beyond saturation as many think... it's throughout the range. Effective permeability is much higher at approx 1T where most devices operate than it is at higher or lower flux densities. Example curve here:
http://www.google.com/imgres?imgurl=http://info.ee...

So I would not expect inductance of iron core device to remain constant as test voltage is varied.

=====================================
(2B)+(2B)' ?

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources