IEC LV MCCB Trip Curves

[Modula2]

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.

 

[EddyWirbelstrom]

For IEC MCCBs see

http://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