×
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

Network Voltage vs. Device Voltage
2

Network Voltage vs. Device Voltage

Network Voltage vs. Device Voltage

(OP)
I am currently designing an electrical distribution system for a plant to be built outside of the U.S.A..  The nominal network voltage is to be 380V/3/50.  The motors and other devices being specified for the plant are 380/400/415V rated (basically IEC stuff).  My question is this, would it be better to design the network voltage at 400V to allow for voltage drop that occurs between the main switchgear and the actual loads?  For example, in the U.S.A. it is common to have a 480V network, but NEMA motors are rated 230/460V.  If you have experience in this particular decision, I would love to hear from you.    

RE: Network Voltage vs. Device Voltage

Motors in Canada are rated 575V and our plant bus voltage is 600V.

RE: Network Voltage vs. Device Voltage

The transformer open circuit voltages are always rated about 5% higher than the system voltages to take care of transformer regulation (when loaded). For example 415V for 400V system, 433V for 415V system.

Hope this is helpful.

RE: Network Voltage vs. Device Voltage

Hi gcaudill,

As per IEC standard system voltages, 380 V is no longer a standard nominal system voltage after 2003. Instead it will be 400 V (+ 6%, -10%) and the equipment are designed accordingly.

Based on above, if you are designing a new distribution network per IEC standard voltages, I agree with your opinion that the network nominal system voltage should be 400 V and not 380 V.

Then how about the utilization voltages?

As per above, supply voltage can drop down to -10% of nominal. IEC 60364 and IEE wiring regulations (BS 7671) allows maximum of 4% drop within the consumer installation (NEC allows a total of 5%). That means the utilization voltage can drop down to 14% from nominal.

Therefore the motor rated (name plate) voltage should be 380 V (+/- 10%).

We should also keep in mind that

1)ANSI transformer primary and secondary voltages are always in line with ANSI standard nominal system voltages. (ANSI C84.1).

2)In IEC transformers, only the primary voltage is in line with a IEC standard nominal system voltage. (We can order with any secondary voltage which is normally 5% higher than standard nominal)

Hope this is helpful!

Kiribanda   

RE: Network Voltage vs. Device Voltage

(OP)
Thanks rraghunath and kiribanda.  Most helpful.

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