×
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

IEC LV MCCB Trip Curves

IEC LV MCCB Trip Curves

IEC LV MCCB Trip Curves

(OP)
I am trying to understand and interpret tripping curves presented by IEC LV MCCB manufacturers, specifically thermal magnetic. These are normally presented as single curves. There must be non-tripping time and current-breaking time with tolerances. For US devices, we usually see the min/max or open/close curves presented, which is useful for coordination/selectivity and for life safty evaluations such as arc flash hazard. Can someone point me in the right direction.

RE: IEC LV MCCB Trip Curves

For IEC MCCBs see   www.schneider-electric.com
IEC MCCBs specifications including +/- current and time tolerances are in Standard IEC 60947-2.
eg. Longtime pickup current is between 1.05 to 1.20 x In.
Magnetic (Inst) pickup tolerance is -0.80 / +1.20 x In.
The IEC Standard describes Catergory A MCCB as MCCBs with no intended time-delay for the Short-Time pickup element.
Category B MCCBs have usually adjustable Short-Time Time delays to assist in grading with downstream MCCBs.
The Standard also refers to 'current limiting MCCBs' which can achieve grading between Category A MCCBs provding the let-thru I2t of the downstream MCCB is less than the I2t unlatching I2t of the upstream MCCB.  This can only be determined from certified manufacturer look- up tables.
ie. the upstream and downstream MCCBs must be from the same manufacturer.
Hope this helps.
Murray Newman

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