×
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

VFD to a conveyor - Problem with load and current

VFD to a conveyor - Problem with load and current

VFD to a conveyor - Problem with load and current

(OP)
Hi

I am testing a screw conveyor to check the power requirements for different materials. The screw conveyor is being fed by a slower screw as is shown in the attached link/image. Both the screws have a different inverter controlling the speed.

http://www.gliffy.com/publish/2215116/

I am having a little problem with the elevator inverter. Its a 380-400V, 50/60Hz, 16 A (pk) Input with
0-500 V, 9.5A, 4kW, 3 phase Output.

The motor at the end of the screw is 3 kW, 6.3-6.8 A, cos (phi) = 0.78. The max spped is 2860 rpm with a gear reduction of 10 at the end. So the max speed is taken as 286 rpm at 50 Hz. Its a two pole three phase motor.

The V/Hz ratio is almost 8.

Q1) When I am testing the material, the empty current load shown by the inverter is 3.8A and when I start feeding in material the load drops to 3.7A. Any idea why it is doing that?? I have tried it three times as well. The inverter frequency is 10 Hz at this point.

Q2) Why is the current almost stable after 20 Hz? I know that the voltage is changing and thus the power too but wanted to confirm if this makes sense.  


Any help would be appreciated. The graphs below show the info ive found using testing.

Thanks
J

http://files.engineering.com/getfile.aspx?folder=4e5a9dbc-e433-4b82-b1fd-e35880591143&file=Test_Results-2.pdf

http://files.engineering.com/getfile.aspx?folder=722496c1-035b-4b59-844b-fff9daa2b585&;file=Test_Results_Chart_1.pdf

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