Pump Emergency stop by Inertia

Hi Friends,

I have three running pumps in my model and for pump emergency (abnormal) shutdown I did the following setting:

the full stop time for one pump shutdown scenario (speed drops from 2900 to zero) is about 2.85 sec, 

for 2 pumps simultaneous shutdown, the stop time is 4.5 second

but the full stop time for the 3 simultaneous pumps shutdown is about 26 seconds

I just confused about the results, since each pump stops based on defined inertia, so the stop time should be the same.

because of this slow stopping in three running pumps scenario, there is no cavitation and negative pressure in the system while for a single running pump there is cavitation and vapor generation. This means that three simultaneous pumps shutdown in better than two simultaneous pumps shutdown and two is better than one, but in reality, it is not correct, more pumps shutdown worse conditions.

I think the stop time should be same for each pump and independent from how many pumps are running simultaneously, 

have any idea how can I fix this problem or is this normal?

Thank You.