Genset size recommendations 1

[dadfap]

I am working on project that is using gensets to drive motors for centrifugal pumps and no-one is ready to recommend genset sizes.

Details
Motors are 127HP, 255Hp & 537HP @ 50Hz (all 380v)
Will be starated on digital soft staarters
Loads are centrifugal pumps.

Generators my client has "budgeted" for are
320KVA (256KW) PRIME, 50 HZ, 400 V FOR THE 127 HP MOTORS
500KVA (400KW) PRIME, 50 HZ, 400 V FOR THE 255 HP MOTOR
810KVA (648KW) PRIME, 50 HZ, 400 V FOR THE 537 HP MOTORS

I am not so concerned by the 255 & 127HP units but I feel that he has not allowed enough for the 537HP motor in terms of handling the inrush current, even allowing for the soft starter, at start up.

Any comments or recommendations?

Thanks

 

[advidana]

Call your catapiller Generator representative, they have software available or they will do the calc for you usually are no cost. They are typical of any generator company. If these are old generators they may do it for a fee.

IEEE also has starting voltage drop curve for generators with motor starting current. This in IEEE red book.

85 percent drop is the value that coils drop off for starters and relay so that is the maximum allow able drop for the motors. The motrr can drop off to 35 percent on starting and still work, but the coils for the motor controls will drop off before that kind on voltages are seen. This also limits the size of generator you can use.

There are more things to consider but this is a starting point.

good luck

 

[rbulsara]

Please refer to FAQ237-766.

Add you all initial loads and largest motor starting capabilities to it.

Hope this will help.