Contact US

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.

Students Click Here

Operating Voltage for 2.7MW Induction Motor

Operating Voltage for 2.7MW Induction Motor

Operating Voltage for 2.7MW Induction Motor

Dear all,

We have this big motor for our upcoming project(conceptual stage). What would be the most suitable operating voltage for it. Assuming that its starting method is Direct-on-Line (DOL). Our available operating voltages (at 50Hz) are:-

a) 3.3kV
b) 6.6kV
c) 11kV

Is it advisable to use 6.6KV or otherwise(with reasons)? Thanks for your help.


RE: Operating Voltage for 2.7MW Induction Motor

Here are some general thoughts.  I'm sure others will provide more specifics.

In general as the horsepower increase the voltage of the most-economic (motor purchase cost) motor increases.

Larger cables are required to carry higher current for the lower voltages.  (a big consideration if motors are far from source)

I would think the breakers for the lower voltage choice might be more expensive since more current must be interrupted for same fault mva.  (Then again, fault mva might be somewhat lower at the lower volt system.. depending on your system).

RE: Operating Voltage for 2.7MW Induction Motor

Suggestion: Reference:
1. Robert W. Smeaton, "Switchgear and Control Handbook," Second Edition, Mc-Graw-Hill Book Co., 1987
Reference 1 Table 3B "Standard Voltages for Large Polyphase Induction Motors" indicates:
Voltage [V], 60Hz:                       HP
460 or 575                                 100-600
2300                                          200-4000
4000 or 4600                              400-7000
6600                                           1000-12000
13200                                         3500-25000
Suggestion: 50Hz will require to reduce those HPs somewhat
M.G. Say, Alternating Current Machine book indicates lower limits of ratings that may typically be (50Hz):
150kW for 3.3kV
300kW for 6.6kV
1MW for 11kV
Definitely, the HP will be decisive in an economical voltage level selection.

RE: Operating Voltage for 2.7MW Induction Motor

Hi friend ,

I feel 6.6kv wil be optimal for DOL START what is your power transformer rating.you have to do voltage drop study before going for this option

When you have 6,6kv supply 3.3 kv is not advisable because you have breakers in thr market most are 11 kv


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! Already a Member? Login


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