Breaker Sizing

I make my calculation for STP plant . My load calculation consist of total 5 pumps .The description as follows :

During continuous operation :

1). duty loads :2 nos & 1 stand by .

2). Duty load : 1 no.

3). Duty load : 1no.

My first two pumps will start each Full load amp is 54A .Therefore 2x54 = 108A .

My third pumps (FLA : 91) will start (biggest load - DOL starting only) ,I considered 6times starting current(6x91=546A) therefore the load at starting will be as 108A+546A = 654A which will be starting current after a certain time my continuous load will be 108+91=199.Know

My fourth pump (FLA : 91) will start (biggest load - DOL starting only) same as i considered starting current 6 times therefore the load at starting will be 108A+91A+546A=745A) which will be the starting current after a certain time my normal load will be stable to 108A+91A+91A=290A , know the total load of the plant at continuous running is 290A .But if you think technical my starting load of the biggest motor adding the load coming 745A in this case i selected the main breaker size of NS630/STR23SE could any one help me out is the selection of the breaker is the biggest size of it should be possible to use less size of the breaker with NS400/STR23SE .Please give me technical answers for the mention subject.The type of breaker selected is from MERLIN GERIN.

My question is that what should be the best practice/rule of thumb during selection