×
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

DC Motors

DC Motors

DC Motors

(OP)
What is the best way to locate the neutral axis of a DC motor in the workshop where motor is usually tested on no load.
regards

RE: DC Motors

Apply AC to the field. With the armature stationary, adjust the brush gear for null voltage on the brushes.
While you're at it, after you have a null point, rotate the armature. A fluctuating voltage on the brushes will indicate shorted or open windings in the armature.
respectfully

RE: DC Motors

the null voltage point varies with load, correct?

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

RE: DC Motors

The null voltage test is used for the initial brush setting. Yes electricpete, the null point will shift with the load as the magnetic field is distorted. On some motors the inter-poles do a fairly good job of maintaining the null point. Once this test is used to set the initial position of the brushes the motor is run under load. If there is sparking at one edge of the brushes, the brushes are shifted to cover the sparks.
respectfully

RE: DC Motors

(OP)
Thanks friends. What should be the voltage & frequency of the AC supply connected to the field to get best results.
Thanks   

RE: DC Motors

For a 120 volt DC field, I would use 120 V, 60HZ (or 50 Hz if that's what you have). The induction of the coil will limit the current to a much lower level than with DC excitation.
Any voltage close to the rated DC voltage.
Is this your practice also, electricpete?
respectfully

RE: DC Motors

"Houshold Current" works very well.

Field voltage is usually in the 100 - 300 V range and insulation is good for at least a few thousand volts. Mains is either 50 or 60 Hz.

Since the field winding is highly inductive, you can apply any normal 50 or 60 Hz voltage to any normal field winding without getting any overcurrent, and the insulation can take any normal voltage.

The normal wall outlet voltage is the easiest way of getting an AC voltage. But remember that you are dealing with lethal voltages. All safety precautions apply.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

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