×
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

575/600 or 480/460 V

575/600 or 480/460 V

575/600 or 480/460 V

(OP)
Hi
I am seeking a basic advise  in regards to rating for motors.

For example I have a 200 HP motor rated at 575 V but the supply is 600 V. Now, normally at the panel where the motor is hooked might  have 600 or 590 v. So, if I have to plug this information in a software package for a 600  v system. Should I plug the info for motor as 575 V or 600 V ?
As the value of current will be different for both voltages.

And I beleive the same reply will work for 460 or 480 v systems.

I would appreciate a word.

Thanks

RE: 575/600 or 480/460 V

The difference is semantics really.600V, 480V, 240V etc. are called the "distribution" voltages, reflecting the measurable levels coming from the utility and/or transformer secondaries. 575V, 460V, 230V etc. are called the "utilization" voltages and reflect the design of the machines or systems connected to use that power.

575V is the "nominal" design voltage for the motor, taking into account the likely voltage drop over distance etc. Motor design voltages are +-10% per NEMA standards, so by saying a motor is 575V, it really means it can be technically used on a system with anywhere from 517.5V to 639V, although in reality is was selected to accommodate 550V and 600V systems in existence in N. America. The same holds true for 460 vs 480V, the nominal motor design voltage is 460 because we have power systems that range from 440 to 480V and 460 was a good compromise.

For your purposes, use your distribution voltage if you are doing a system study, but remember to factor in voltage drop  if you are working on studying something at the motor terminals. The motor design voltage is relevant only when looking at motor heating, torque ratings etc.

JRaef.com
"Engineers like to solve problems.  If there are no problems handily available, they will create their own problems."   Scott Adams  
For the best use of Eng-Tips, please click here -> FAQ731-376

RE: 575/600 or 480/460 V

As jraef said, it's the difference between nominal system voltage and the utilization voltage to allow for the inevitable voltage drop.

The software I use for analysis (EasyPower) uses the equipment nameplate voltage in its database.  If the bus voltage differs too much from the equipment voltage, you get a warning when entering the data.  

It will depend on the software to some extent, I think.

RE: 575/600 or 480/460 V

I believe that using the system voltage and the motor rated current will give good results. You have an allowance for voltage drop and the motor will draw slightly less current at a higher voltage. Any errors will be conservative.
respectfully

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