What effect does a soft starter have on the neaurtal

[soccerdude]

Can anyone please tell me what happen on the service neautral ? When starting a 300 hp. (480V) pump motor with a sq. D soft-start starter. Is there a harmonic load created on the neautral duing the starting? If so how large of load would there be? Do I need a neautral in the service for this load? Thank you

 

[cpal]

Can anyone please tell me what happen on the service neautral ? When starting a 300 hp. (480V) pump motor with a sq. D soft-start starter. Is there a harmonic load created on the neautral duing the starting? If so how large of load would there be? Do I need a neautral in the service for this load? Thank you

Good question but I don't know I would try http://ecatalog.squared.com/techlib/browse.cfm?hid=0b008926801145c5tis url and pose the question to Sq D Tech support

 

[kingpb]

A soft starter is not the same as a VFD. The soft starter only is in operation for a few seconds, then switches to the normal across the line configuration. There should not be a concern.

If you have a choice for service, just go with a 480V, 3ph 3W.

 

[jim dungar]

Are you asking what might happen? Or, do you have an incident that you are trying to explain?

There are no neutral connections to the soft-starter (ATS46) so one is not required and there will not be any line-neutral harmonics generated by the starter. However the line to ground voltage rating for the starter is probably <300V so it does require a grounded 480Y/277 service.

 

[boater bill]

Most soft-starts use power SCR's to control the ramp speed up and down, then switch to a contactor while running at full speed.
And there are no neutral connections to the starter, so there should be no harmonics issues unlike VFD's with the high switching frequency IGBT pwoer transistors.