The requirement of the 125% of the largest motor could be performed in two ways:
Say of motor of 100 amps
1. 100 x 1.25 = 125 amps
OR
2. 100 x 25% = 25 amps
then add the original 100 amps plus the 25 amps, and you will have 125 amps
I love this stuff... when it works
Pierre