×
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

Large motor starting

Large motor starting

Large motor starting

(OP)
I am running SKim.M y question is, what we need to run by SKIM in order to determine if the motor can start properly.
Thank you in advance.

RE: Large motor starting

You should know the load inertia (WK^2), the load spee-torque and the motor speed-torque curves.

The torque requirements to accelerate the load will dictate if reduced or full voltages are required.

The accelerating or starting time in seconds will be:

   t= WK^2 x (Drpm)/(308 X Tave)

   Drpm = speed change
   Tave = Average motor torque minus load torque (Lb*Ft)

Note that at reduced voltage the motor torque is reduced with the squared power of the voltage reduction ratio.  

RE: Large motor starting

(OP)
Thanks,Aolalde,

RE: Large motor starting

You should also know the acceptable bus voltage drop on the system, both primary and secondary, along with as complete a study of the power supply as is possible. Transformer / generator sizes, impedances, cable sizes and lengths, existing loads on line at the time of starting etc.

Just a plug for an excellent product...
We use SKM as our primary modeling tool for predicting RV starting success. In nearly all applications where we have run a simulation, it has been dead on correct! On 3 occasions, competitors claimed to be able to do something that we said couldn't be done because the SKM models did not bear out, and that turned out to be true (and costly for the competitors and end users).

The only minor drawback is in modeling solid state soft starting, because it can only model a fixed current acceleration, not a true ramped acceleration. But to be honest, I cannot see how any PC based sofware program could model all the variable dynamics of ramping the voltage or current, so IMHO it is as good as is reasonably possible.

"Venditori de oleum-vipera non vigere excordis populi"


RE: Large motor starting

Aolade,

What is the DRPM ?


Bob

RE: Large motor starting

Delta (change) in RPM.

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