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Causes and corrective actions
5
PROTECTIVE FUNCTIONS
Operation Panel
Indication
E.OC3
FR-PU04
FR-PU07
OC During Dec
Name
Overcurrent trip during deceleration or stop
Description
When the inverter output current reaches or exceeds approximately 220% of the rated inverter current
during deceleration (other than acceleration or constant speed), the protective circuit is activated to
stop the inverter output.
Check point
· Check for sudden speed reduction.
· Check for output short circuit.
· Check for too fast operation of the motor's mechanical brake.
· Check if the stall prevention operation level is set too high.
· Check if the fast-response current limit operation is disabled.
· Check that the power supply for RS-485 terminal is not shorted. (under vector control)
· Check that the rotation direction is not switched from forward to reverse rotation (or from reverse to
forward) during torque control under Real sensorless vector control.
Corrective action
· Increase the deceleration time.
· Check the wiring to make sure that output short circuit does not occur.
· Check the mechanical brake operation.
·
Lower the setting of stall prevention operation level.
· Activate the fast-response current limit operation. (Refer to page 152.)
· Check RS-485 terminal connection. (under vector control)
· Prevent the motor from switching the rotation direction from forward to reverse (or from reverse to
forward) during torque control under Real sensorless vector control.
Operation Panel
Indication
E.OV1
FR-PU04
FR-PU07
OV During Acc
Name
Regenerative overvoltage trip during acceleration
Description
If regenerative energy causes the inverter's internal main circuit DC voltage to reach or exceed the
specified value, the protective circuit is activated to stop the inverter output. The circuit may also be
activated by a surge voltage produced in the power supply system.
Check point
· Check for too slow acceleration. (e.g. during descending acceleration in vertical lift load)
· Check that the Pr. 22 Stall prevention operation level is not lower than the no load current.
Corrective action
· Decrease the acceleration time.
· Use regeneration avoidance function (Pr. 882 to Pr. 886). (Refer to page 383.)
· Set a value larger than the no load current in Pr. 22 Stall prevention operation level.
Operation Panel
Indication
E.OV2
FR-PU04
FR-PU07
Stedy Spd OV
Name
Regenerative overvoltage trip during constant speed
Description
If regenerative energy causes the inverter's internal main circuit DC voltage to reach or exceed the
specified value, the protective circuit is activated to stop the inverter output. The circuit may also be
activated by a surge voltage produced in the power supply system.
Check point
· Check for sudden load change.
· Check that the Pr. 22 Stall prevention operation level is not lower than the no load current.
Corrective action
· Keep load stable.
· Use regeneration avoidance function (Pr. 882 to Pr. 886). (Refer to page 383.)
· Use the brake unit or power regeneration common converter (FR-CV) as required.
· Set a value larger than the no load current in Pr. 22 Stall prevention operation level.
Operation Panel
Indication
E.OV3
FR-PU04
FR-PU07
OV During Dec
Name
Regenerative overvoltage trip during deceleration or stop
Description
If regenerative energy causes the inverter's internal main circuit DC voltage to reach or exceed the
specified value, the protective circuit is activated to stop the inverter output. The circuit may also be
activated by a surge voltage produced in the power supply system.
Check point
Check for sudden speed reduction.
Corrective action
·
Increase the deceleration time. (Set the deceleration time which matches the moment of inertia of
the load)
· Longer the brake cycle.
· Use regeneration avoidance function (Pr. 882 to Pr. 886). (Refer to page 383.)
· Use the brake unit or power regeneration common converter (FR-CV) as required.