Motor Trip on Instantenous OC
Motor Trip on Instantenous OC
(OP)
200hp, 480V motor tripping on instantaneous RS510 DigiTrip unit. Motor winding Insulation resistance above 50G-ohm and healthy winding resistance. Trip Unit is healthy and no issue with the cable. What else can cause this?
Note: Motor runs for 20-25 min before tripping.
Note: Motor runs for 20-25 min before tripping.






RE: Motor Trip on Instantenous OC
Running for a length of time and then tripping on IOC generally points to something in the circuit. For example it could be moisture getting into a conduit or sheath, but only after whatever process involves this motor gets under way for a period of time, i.e. it takes 20-25 minutes for the moisture to reach a spot in the cable insulation that leaks. Anything inside of the motor is generally going to be immediately evident. So I would start with a good insulation test on your motor leads, without the motor connected since you already did that.
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: Motor Trip on Instantenous OC
If it's gone through start-up successfully and then trips on instantaneous, serious stuff is afoot, as jraef says. It is all too common to have a winding shorted and NOT have a ground path. Less common ar intermittent shorts in motor leads or in the feeders.
old field guy