May I know how much current that this contactor can handles?

Discussion in 'General Electronics Chat' started by wkyong, Aug 18, 2008.

  1. wkyong

    Thread Starter Active Member

    Apr 29, 2008
    This is a ABB B50 brand contactor,it is written Ith=125A ,
    IeAC-1=100A & not mentioned continuous current ,
    I don't understand what do they mean & which one is the exact current that it can handles?
  2. nazree


    Jun 23, 2008
    Ith = Thermal Rated Current
    IeAC may have something to do with Auxiliary Contacts current..
  3. vinnygalbo

    New Member

    Aug 28, 2008
  4. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    The Ith figure is it's continuous, steady-state carrying capacity.

    AC1 and AC3 are 'real world' ratings for when it's switching power to various categories of load.

    eg. a when the contactor closes to start a big three phase motor, the start current will be much higher than the maximum running current, while it gets up to speed. When it opens to stop the motor, there will be some level of arcing at the contacts due to switching an inductive load (the motor windings).

    One of the ratings (AC3?) gives the maximum motor current rating, which is rather lower than the Ith figure to allow for the starting & stopping loads and still maintain the rated life of the contactor.