×
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

Inverter duty motors
2

Inverter duty motors

Inverter duty motors

(OP)
I am trying to confirm if there is a code requirement that an inverter duty motor is required when installing a VFD. It is an existing condition. The client is looking to add VFDs to existing motors, but does not want to change the motors.  

RE: Inverter duty motors

Some motors from before the VFD era are actually VFD compliant, according to a few case-by-case inquiries I've made to manufacturers.

Details like voltage rating of insulation, mechanical support of windings, and potential for speed increases are among what determine VFD suitability.

RE: Inverter duty motors

I'm not aware of any standard which requires that. If your client does not have an internal standard he must follow, I'll guess he is fine with what he is planning. It depends a little bit upon the motor size in combination with the power that is drawn by the machine. If you have a 90 HP motor and the required power is only 50 HP, it will work well even at low speed. I assume your question is not related to an explosion proof motor?

RE: Inverter duty motors

Be careful about slowing a non-VFD rated motor too much: the motor cooling on a slowly rotating motor relies upon radiation from the motor housing since the fan is not moving enough air to cool the motor with forced convection.  VFD rated motors typically have a larger frame size.  If you want 2:1 speed range on the motors it is significantly different than 1000:1 speed range.  Make sure that the VFD control panel interface will not allow damaging slow speeds.  Conversely speeding up the motors past the synchronous speed may result in the inability of the motor to provide sufficient torque. Talk to your motor's manufacturer about specifics.

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