Sizing for Motor Loads Softstarter and Protective Device

[garryee]

Please help me on how to size / calculate for the required rating of the softstarter and protective device for a certain motor load. Thank you in advance.

 

[davidbeach]

First off it probably depends on the relevant code, which you haven't stated.

 

[garryee]

thanks for the feedback.

i.e:

motor specs / Source:
700 HP, V = 4160, 3 phase, 60 Hz

 

[davidbeach]

No, i.e. where in the world are you? What standards and codes apply?

 

[jraef]

4160V 60Hz would imply the US, Canada or Mexico, maybe other South American countries like Chile that get a lot of their equipment from Canada and the US.

Assuming someone has properly sized the motor, you size the soft starter for the motor you will connect to it. I don't see the issue here. 700HP motor, 700HP starter.

Protective device? Do you mean the fuses or circuit breaker? Generally you will not have much of a choice, when you buy the soft starter, the devices inside will have been coordinated with specific fuses and you usually cannot deviate from those without violating the starter design. this is a discussion you need to have with the soft starter mfrs.

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