ThePunisher
Electrical
- Nov 7, 2009
- 384
HI all,
UL 489 have sets of test currents associated with LV MCCBs and PCBs at full voltage rating. IEEE Std. 1015 also mentions single pole interrupting but not too much details were given. In UL 489, the test currents were set and ratings are minimum to obtain UL certification.
In short circuit calculations, line-ground faults are based on line-neutral voltages. IEEE 551 and 141 considers bolted three phase faults as basis for kAIC ratings for LV MCCBs and PCBs. However, these kAIC ratings are based on 3 poles operating and perhaps not based on 1 pole.
Line-ground faults in solidly grounded systems will pickup one MCCB pole as the currents are unbalanced and MY QUERY would be on cases where the line-ground fault current are GREATER than the 3 phase fault (in generator MCCB/PCB or immediately near the transformer secondary terminals.
QUERY: In cases where the line-ground fault is greater than the 3 phase fault and considering UL 489, does the kAIC now based on line-ground fault current and not the 3 phase fault current? How do we specify kAIC if the single pole kAIC is not even indicated in the MCCB nameplate?
Regards,
UL 489 have sets of test currents associated with LV MCCBs and PCBs at full voltage rating. IEEE Std. 1015 also mentions single pole interrupting but not too much details were given. In UL 489, the test currents were set and ratings are minimum to obtain UL certification.
In short circuit calculations, line-ground faults are based on line-neutral voltages. IEEE 551 and 141 considers bolted three phase faults as basis for kAIC ratings for LV MCCBs and PCBs. However, these kAIC ratings are based on 3 poles operating and perhaps not based on 1 pole.
Line-ground faults in solidly grounded systems will pickup one MCCB pole as the currents are unbalanced and MY QUERY would be on cases where the line-ground fault current are GREATER than the 3 phase fault (in generator MCCB/PCB or immediately near the transformer secondary terminals.
QUERY: In cases where the line-ground fault is greater than the 3 phase fault and considering UL 489, does the kAIC now based on line-ground fault current and not the 3 phase fault current? How do we specify kAIC if the single pole kAIC is not even indicated in the MCCB nameplate?
Regards,