Just think of it as a water system with many sources/tanks. Those tanks connected to the point where a pipe break occurs will surely contribute water that gushes out! Those tanks with no water in them (motors not running or off) will not.What about different types of motors, water and fire pumps(fire pumps unlikely to be running at time of fault, no?) and AC compressors?
A good primer
Assuming a motor contribution of fourtimes rated full load current is acceptable. Thestandard arrived at this value by assuming themotor contribution of 3.6 times rated current camefrom 75% induction motors and 4.8 times ratedcurrent from 25% synchronous motors
never knew how the 4 was arrived at
learn something everyday
I use 4 for all motorsSo when figuring motor contribution what values do we use?
Motor contribution will only be found in 3-ph and ph-ph faults! For details see ToddToddy's 12-01-12 post!
Rerards, Phil Corso
maybe this one? - http://forums.mikeholt.com/showthread.php?t=149424What is this?