Fuji Electric Frenic-Mini - Chapter 7 SELECTING OPTIMAL MOTOR AND INVERTER CAPACITIES

6-10
[ 2 ] 0u n Overvoltage protection
Problem The DC link bus voltage was over the detection level of overvoltage.
0u1 Overvoltage occurs during the acceleration.
0u2 Overvoltage occurs during the deceleration.
0u3 Overvoltage 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 overvoltage 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 bus voltage exceeds the overvoltage 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 suddenl
y
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 bus voltage was below the protective level
when the alarm occurred.
 Improve noise control. For details, refer to "Appendix A" o
f
the FRENIC-Mini User’s Manual (MEH446).
 Enable the retry function (H04).
[ 3 ]
lu Undervoltage protection
Problem DC link bus voltage was below the undervoltage detection level.
Possible Causes What to Check and Suggested Measures
(1) A momentary power
failure occurred.
 Reset the alarm.
 If you want to restart running the motor by not treating this
condition as an alarm, set F14 to "4" or "5," depending on
the load.