Emax Low voltage air circuit-breakers - ABB Download Center

Direction (OUT-IN)Fw ➞ FwFw ➞ BwBw ➞ BwBw ➞ FwReference DirectionArrow-B1INFw BwOUTFw BwINFw BwOUTFw BwAI>I>-TM1IkQF1 +PR123QF4 +PR123INFw BwOUTFw BwI>QF3 +PR123QF2 +PR123QF5 +PR123I>I>-TM2INFw BwOUTFw Bw-B2INFw BwOUTFw Bw2) Fault in the motor: in this case, only circuit-breaker QF5 must interrupt the fault. Circuit-breakerQF5 is passed through by a current flowing from busbars B1 and B2, in a direction concordantwith the one set; therefore, the OUT Fw bus of QF5 “blocks” both the IN Fw bus of QF2(passed through by a current flowing from TM2 and consequently in a direction concordantwith the one set) as well as the IN Bw bus of QF3 (which is passed through by a currentflowing from TM1 and consequently in a direction discordant with the one set). Similarly,circuit-breaker QF3 is alsopassed through by a currentflowing from TM1 in a directiondiscordant with the oneset: consequently, the OUTBw bus of QF3 “blocks” theIN Fw bus of QF1 (passedthrough by a current flowingfrom TM1 and therefore in adirection concordant with thesetting).LM1SDC200321F0001Direction (OUT-IN)Fw ➞ FwFw ➞ BwBw ➞ BwBw ➞ FwReference DirectionArrow3) Fault on the supply side of transformer TM2: in this case, only circuit-breaker QF2 must interruptthe fault. Circuit-breaker QF2 is passed through by a current flowing from TM1 and fromthe motor, in a direction discordant with the one set; as a consequence the OUT Bw bus ofQF2 “blocks”:– the IN Bw bus of QF5 (passed through by a current flowing from the motor and consequentlyin a direction discordant with the one set)– the IN Bw bus of QF3 (passed through by a current flowing from TM1 and consequently ina direction discordant with theone set).Similarly, circuit-breaker QF3-B1INFw BwOUTFw BwINFw BwOUTFw BwAI>I>-TM1IkQF1 +PR123QF4 +PR123INFw BwOUTFw BwI>QF2 +PR123QF3 +PR123QF5 +PR123I>I>-TM2INFw BwOUTFw BwINFw BwOUTFw Bw-B2is also passed through by acurrent flowing from TM1 in adirection discordant with theone set; therefore its OUT Bwbus “blocks” the IN Fw bus ofQF1 (passed through by acurrent flowing from TM1 andtherefore in a direction concordantwith the one set).6LM1SDC200322F0001ABB SACE 6/19