TROUBLE SHOOTING
7-10
2. “OUn” Over voltage protection
Problem The DC link circuit voltage was over the detection level of over voltage.
OU1 Over voltage occurs during the acceleration.
OU2 Over voltage occurs during the deceleration.
OU3 Over voltage occurs during running at constant speed.
Possible Causes What to Check and Suggested Measures
1. The power supply
voltage was over the
range of the inverter’s
specifications.
Measure the input voltage.
→ Decrease the voltage to within that of the specifications.
2. The acceleration time
was too short.
Check if the over voltage alarm occurs after sudden acceleration.
→ Increase the acceleration time (F07, E10, and H54).
→ Select the S-curve pattern (H07).
→ Consider the use of a braking resistor.
3. The deceleration time
was too short for the
moment of inertia for
load.
Recalculate the deceleration torque from the moment of inertia for
load and the deceleration time.
→ Increase the deceleration time (F08, E11, and H54).
→ Enable automatic deceleration (H69=1) so that when the DC link
circuit voltage exceeds the over voltage suppression level, the
inverter changes the deceleration time to three times longer than
the set value.
→ Set the rated voltage (at base frequency) (F05) to 0 to improve
braking ability.
→ Consider the use of a braking resistor.
4. Loads were suddenly
removed.
Check if the alarm occurs when loads are suddenly removed.
→ Check if the inverter operation suddenly changes from driving
operation to braking operation.
→ Consider the use of a braking resistor.
5. Braking load was too
heavy.
Compare the braking torque of the load with that of the inverter.
→ Set the rated voltage (at base frequency) (F05) to 0 to improve
braking ability.
→ Consider the use of a braking resistor.
6. Malfunction caused by
noise.
Check if the DC link circuit voltage was below the protective level
when the alarm occurred.
→ Improve noise control.
→ Enable the auto-reset function (H04).
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