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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 170% 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. (V/F control, Simple magnetic flux vec-
tor control)
· Check that the inverter capacity matches with the motor capacity. (IPM motor control)
· Check if a start command is given to the inverter while the motor is coasting.
Corrective action
· Increase the deceleration time.
· Check the wiring to avoid output short circuit.
· Check the mechanical brake operation.
· Lower the setting of stall prevention operation level (Refer to page 91.)
· Activate the fast-response current limit operation. (V/F control, Simple magnetic flux vector control)
· Choose inverter and motor capacities that match. (IPM motor control)
·
Input a start command after the motor stops. Alternatively, set the automatic restart after instantaneous
power failure/flying start function.
(Refer to 162 page .)
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 with lifting load)
·
Check if Pr.22 Stall prevention operation level is set too low like the no-load current.
Corrective action
· Decrease the acceleration time.
· Use regeneration avoidance function (Pr. 882 to Pr. 886). (Refer to page 279.)
· 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 if Pr.22 Stall prevention operation level is set too low like the no-load current.
Corrective action
· Keep load stable.
· Use regeneration avoidance function (Pr. 882 to Pr. 886). (Refer to page 279.)
· 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 279
.)
· Use the brake unit or power regeneration common converter (FR-CV) as required.