Motor Overload

[speedtronic]

A motor at our site was tripping on overload protection after 7-8 seconds when it was taken in service. When motor winding resistance was checked from phase to phase using multimeter, it was found that L1-L2 2.7 ohm L2-L3 2.7 ohm & L3-L1 5.7 ohm. What does it signifies & how it is effecting motor's operation & causing it to trip on over load?

 

[Darkwood]

Your overload tripping issue is more likely to be caused by another issue, but to be able to give you any direction i will need info:-
What is the motor doing (pump, drive etc)
Does it start up underload or off load if under load have you tried starting it off load
What is the rating of the motor and overload
What starting system is used D.O.L., star delta etc
Does the motor behave oddly when starting
Is there a gearing system in line

Just a few questions to get the ball rolling.

 

[THE DUKE]

First check all connection on the block star point or delta link if all tight your motor has a shorted winding consult your nearest rewind shop for a rewind or replacement motor.(28 year working in industry tell me so) Good luck

just an other thought is the motor connection delta it could be open ciruit in one winding so your high reading is the other two winding in series yes I know 2.7 + 2.7 = 5.4 but it is close

 

[Darkwood]

Sounds like duke could be on to something and with him been in motor winding and repair service in his career his experience beats me on this one.

 

[thepurple1]

You could load check each phase to see what amps it was drawing. If its not drawing above the F.L.C that is on the rating plate and all your connections are tight on the motor/contactor/ and all terminals, and the pump or fan is not doing over duty i.e not offit curve then change the overload