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!

*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.

Jobs

I have three phase motor wired high

I have three phase motor wired high

(OP)
I have three phase motor wired high voltage. (400v). Drive programmed 230.
Has run 24/7 times six weeks at 60 percent MAX speed. Found problem when new product setup required much faster speed.

A second motor, changed yesterday and incorrectly wired the same way gave no problem. What happened to motor running incorrectly 6 weeks. Just curious. The problem seen was on panel view amps showed 99 percent before fault. Most recent one never exceeded 25 perceny

RE: I have three phase motor wired high

(OP)
Fyi, reason tech wired incorrectly was replacements came in 230/400. Original was 116/230 so high voltage was correct. I had never seen these motors before am told machine and parts from Germany and 116 three phase is common l.

RE: I have three phase motor wired high

(OP)
My question is what happened to the motor wired incorrectly and run at low speed that caused it to give overcurrent alarm when run at high speed. At the same time, a second motor wired the same ,that day, did not show over current. ram fine.

I understand this was big screw up. But my curiosity is,, what did this mistake do to the motor being used for six weeks that showed up when increasing the speed

RE: I have three phase motor wired high

You should've posted this in forum237: Electric motors & generators engineering not Electronics.

That said, as you increase the speed by raising the frequency the motor needs higher voltage to provide the horsepower demanded by the larger load caused by the higher speed. If the voltage isn't there it will draw more current to provide the volts x amps = Power needed. That means the motor will get over-currented and toast.

Typically the VFD will protect the motor from that but if the motor is miswired or the VFD protection setting are screwed up as suggested by the rest of this messed up install then the protection could easily be defeated. As long as the VFD is not itself being overloaded it will happily toast a motor.

Keith Cress
kcress - http://www.flaminsystems.com

RE: I have three phase motor wired high

Are you sure that the second motor was not 116/230 volts?

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

RE: I have three phase motor wired high

(OP)
Thank you all so much. Sorry for wrong forum post. I was just curious that it ran a while before it malfunctioned and what facicaly tapped inside that allowed it to run slow but not fast. Obviously it was about the same if as it must have been when Jimmy Carter had that famous conversation with daughter Amy about nuclear proliferation

RE: I have three phase motor wired high

At 50% voltage the motor will run but the torque will be way down.
At 60% speed the motor still had enough torque to drive the load.
As the speed increased past 60% the load demanded more torque than was available at rated current.

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

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


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close