Rockwell Automation 1333 Drive, 3/4-5HP, 230-575V Series D - Manual (Page 109)

Preventive Maintenance and
Troubleshooting Common Drive Problems
Appendix B
B-2
Over Current Protection -- OC is Displayed
The Reason If overcurrent exceeds 200% of rated Drive current or if a
ground fault occurs at the drive output leads, this protective circuit will
shut off the drive transistors.
Precheck Procedure
1. Load inertia is excessively large and programmed acceleration time is
extremely short. Setting Parameter 17 to 1 or increasing the value of
Parameter 1 will guard against OC nuisance trips.
2. The motor experienced an excessive overload condition. If the drive
tripped on acceleration, setting Parameter 7 to a higher current limit
setting may avoid OC nuisance trips. If the drive trips only on
deceleration, enabling Parameter 46 may avoid OC nuisance trips on
deceleration.
3. A short circuit exists in the drive output leads or in the motor windings.
4. A ground fault exists in the drive output leads or in the motor windings.
5. A device in the Drive output inverter section has shorted.
Over Load Protection -- OL is Displayed
The Reason If Parameter 6 is set to 0 and current exceeds 140% of rated
Drive current for 60 seconds, this protective circuit will shut off the drive
transistors.
If Parameter 6 is set to a value other than 0 and current exceeds 115% of
Parameter 7 for 60 seconds, this protective circuit will shut off the drive
transistors.
Precheck Procedure
1. The starting load is above 140%. The Drive is attempting to start the
load, but Parameter 17 is preventing it. Disable Parameter 17.
2. The running load has been above 140% for one minute. The Drive may
be in accel frequency hold if below the current limit set by Parameter 7,
or in accel frequency hold if at the current limit set by Parameter 7.
Check Parameters 17 and 6. If neither accel frequency hold nor overload
protection is selected, the Drive has been between 140% and 180% of
rated current for one minute, tripped out, and is functioning normally.
3. The running load has been above 115% of Parameter 7 for 60 seconds
causing the motor to overheat and the drive to trip. Check Parameters 17
and 7, then check to see if Parameter 6 is set to a value other than 0.