×
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

NEC Article 450 - Transformers

NEC Article 450 - Transformers

NEC Article 450 - Transformers

(OP)
hello,
this is probably a real basic question but in NEC Article 450, Table 450.3(A) and (B), when transformers are refered to as Over 600 volts or 600 volts and less, is this the primary voltage?  I'm assuming it would be the highest voltage.  For instance, a 13.8 kv /480V transformer would be on Table 450.3(A) and a 480V/120V transformer would be on Table 450.3 (B).
Also, where would the definition of the 600 Volts is primary or highest voltage be found in NEC?  I've looked in several places but obviously not the right spots.

Thank you in advance.

RE: NEC Article 450 - Transformers

It's the highest voltage.  Table 450.3 (A) has separate columns for primary and secondary sides and separate requirements for secondary winding over or under 600V.  If any winding is over 600V, it falls into this category.  Table 450.3(B) for 600V and below has no provision for any winding being over 600V, unlike Table A.  I don't think this is specifically defined anywhere, but that's the intent.  If you look at the tables, I don't think any other interpretation would be reasonable.

One fallacy in Article 450 is the presumption that the primary is always the highest voltage.  Technically, this is not always the case.  For generator step-up transformer, the primary is the lower voltage.  But this doesn't really change the intent of Article 450.   

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