star/delta o/load

[mec1]

i have a 3 phase motor pump rated at 17.9A full load do i fit an o/load in the main contactor line and set it at 11A this being 17.9/sqrt3

 

[rbulsara]

Yes, if this is a standard Y/D starter with O/L relay on the load side (in series with motor windings), of the main contactor. In other words if the O/L relay is seeing the phase currents of the delta conection then your statement is true.

 

[jbartos]

Suggestion: Check the Square D Digest 173 pages 14-44 and 14-45 available on line:

http://www.squared.com

http://ecatalog.squared.com/pubs/Motor Control/Starters/50006-026-01E.pdf

Figure 3 and Figure 4

 

[aolalde]

Regularly on wye-delta starters the full load current of the motor is shared between two contactors ( 1M and 2M), then the thermal units must be sized for 58% of the full load ampere rating of the motor .