×
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

Bad Start or Run Capacitor

Bad Start or Run Capacitor

Bad Start or Run Capacitor

(OP)
We are still having trouble with a single phase 230v 60hz 10hp motor. It occasionally trips the thermal reset. I posted last year the following thread: thread237-317705: Thermal Protection Relay - tripping
Yesterday we ran the motor for the first time since last year. It is used in a maple sugar operation. The motor operates a liquid ring vacuum pump. What I noticed yesterday is that we the motor first starts there is an unbalanced current between both legs of about 12%. One was about 33 amps, while the other was 29 amps or so. After running for 20 minutes or so the difference was only a 0.1 amp or so. Is this an indication of a bad start capacitor?

RE: Bad Start or Run Capacitor

Sounds like a moisture problem in the windings. If the motor is not used for long periods of time (months) and is in an unheated space, or there is a lot of humidity around, then such a problem may occur. As the motor warms up, the moisture will be driven off, but a ground fault may occur inside during the warmup time. Consider putting a small heater or heatlamp under the motor during the not in use period of the year.

rasevskii

RE: Bad Start or Run Capacitor

(OP)
That certainly could be possible. The motor is used outdoors in a semi enclosed space. The motor is a drip proof motor. Would a total enclosed motor be less susceptible to this?

RE: Bad Start or Run Capacitor

Yes, a TEFC motor would be the better choice. But still a small heater would be desirable.

rasevskii

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