×
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

starting HV induction motor PF
2

starting HV induction motor PF

starting HV induction motor PF

(OP)
Hi!

I have to calculate the voltage drop in case of DOL starting a 6.6 kV induction motor (squirrel cage).
I used starting PF=0.3.
My boss said that PF=0.3 is too low for a MV motor.
I recall a calculation example from an IEEE book, that use for a LV motor, the starting PF=0.2. Therefore, I believe that PF=0.3 is quite generous, since there is no big constructive difference between a MV & a LV induction motor.
Obvious, using a low starting PF, will result an unacceptable voltage drop and consequently I have to consider an alternative starting method, such as: Y-D, autotransformer, series resistors or a capacitor bank.  

Can anyone please advice me where I can find (a standard, paper or book) an advice on MV-HV induction motor’s, starting PF?

Thank you for your time.

RE: starting HV induction motor PF

I would contact a motor manufacturer.  I typically use 0.2 for starting analysis.  

I don't see why MV motors would behave much differently at locked rotor than LV motors, in terms of power factor.  
 

RE: starting HV induction motor PF

It doesn't matter if it is MV or LV, the math is the same. But dpc is right, you are best to start with a motor manufacturer. MV motors are built to order: you can ask for pretty much anything you need but there are design limits and tradeoffs. I have worked on several MV motor projects doing TMS analysis where the motors were not yet selected, and every time a vendor came to us with a different motor, the numbers were always different and no two of the studies came out the same. I saw MV motors with as little as .15 and as high as .25 power factor at startup, but for a blind study I also always use a .20 pf.

Good paper on the subject from one of our members, Marke:
http://www.lmphotonics.com/m_control.htm

Word to the wise however: stay away from Y-Delta starting on MV motors. Transition spikes can damage other nearby electrical equipment and/or the torque spike can snap shafts on power train components. Primary resistors are nasty as well (think of the heat). Stick to Autotransformer, reactor or solid state starting.

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