Delta MH300 Series - Page 734

Chapter 14 Fault CodesMH300
14-7
ID No. Display Fault Name Description
3
Over-current during
steady operation
(ocn)
Output current exceeds 3 times of the
rated current
during constant speed.
When ocn occurs, the drive
closes the gate of the output immediately, the
motor
runs freely, and the display shows an ocn error.
Action and Reset
Action condition 300% of the rated current
Action time Immediately act
Fault treatment parameter N/A
Reset method Manual reset
Reset condition Reset in 5 sec. after the fault is cleared.
Record Yes
Cause Corrective Actions
Short-circuit at motor output
due to poor insulation wiring.
Without considering the short circuits, check the motor cable or replace
the cable before turning on the power.
Check for possible shaft lock,
burnout or aging insulation of
the motor
Troubleshoot the motor shaft lock.
Check the motor insulation value with megger. Replace the motor if the
insulation is poor.
Impulsive change of the load Reduce the load or increase the capacity of the AC motor drive.
Use special motor or motor
with larger capacity than the
drive
Check the motor capacity (the rated current on the motor’s nameplate
should ≤ the rated current of the drive).
Use ON/OFF controller of an
electromagnetic contactor at
the output (U/V/W) of the drive
Check the action timing of the contactor and make sure it is not turned
ON/OFF when the drive outputs the voltage.
V/F curve setting error
Adjust V/F curve settings and frequency/voltage. When the fault occurs,
and the frequency voltage is too high, reduce the voltage.
Torque compensation is too
large.
Adjust the torque compensation (refer to Pr.07-26 torque compensation
gain) until the output current reduces and the motor does not stall.
Malfunction caused by
interference
Verify the wiring of the control circuit and wiring/grounding of the main
circuit to prevent interference.
The length of motor cable is
too
long.
Increase the AC motor drive’s capacity.
Install AC reactor(s) on the output side (U/V/W).
Hardware failure
The ocn occurs due to short circuit or ground fault at the output side of
the drive.
Check for possible short circuits between terminals with the electric
meter:
B1 corresponds to U, V, W; DC- corresponds to U, V, W;
corresponds to U, V, W.
If short circuits occur, return to the factory for repair.