×
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

50 hp 480 volt sawmill problems?

50 hp 480 volt sawmill problems?

50 hp 480 volt sawmill problems?

(OP)
looking for anyone that knows anything about sawmills!! This particular saw mill has a 50 hp head saw that is wired 480 volt and some days it has great power and some days it dont. It was recently changed to 480 volt from 120/240 but was having the same problem. it seems to lose rpm's but it doesnt drop 3 to 5 volts on any leg while crowding it through a big log and the amp draw is right on with full load when in the middle of the log. Could this be an insulation problem in the motor? ANY COMMENT WILL BE GREATLY APPRECIATED!

RE: 50 hp 480 volt sawmill problems?

Assuming you just meant 240V 3 phase and now it is 480V 3 phase, how is it that you changed? Did you buy a new transformer to feed it? If so, what size is the transformer? Sounds as though maybe your system capacity is not up to the task.

Yes it is also possible that you have the beginnings of a serious insulation breakdown problem. If you don't know what a megger is or how to safely use one, find someone who does and do a little testing on it. Moght be time for a rewind.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)

For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies

RE: 50 hp 480 volt sawmill problems?

Or the belts are slipping. Is this a band saw or a circular saw?

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: 50 hp 480 volt sawmill problems?

Hello bdj30

Sounds to me like it could be that you have a rotor problem.
When you put the motor under load, you will increase the rotor current and the rotor bar heating.
This will cause expansion and if you have a bar break, it could go high resistance and this will increase the slip to achieve the same torque. The motor will slow without significant current rise.

I suggest that you get the rotor inspected.

Best regards,
Mark.

Mark Empson
Advanced Motor Control Ltd

RE: 50 hp 480 volt sawmill problems?

(OP)
we changed the voltage by changing transformers. the muni installed a new 1500 kva 277/480 transformer.it is a circular saw thank you all for your input i will check everything you mentioned

RE: 50 hp 480 volt sawmill problems?

My .02 cents ---- Your supply is bad?? Seen it before - often!!

RE: 50 hp 480 volt sawmill problems?

(OP)
Mike could you elaborate please

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