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6. PROTECTIVE FUNCTIONS
6.4 Causes and corrective actions
Abbreviation E.OC2 FR-LU08 OC During Cnst Spd
FR-PU07 Steady Spd OC
Name Overcurrent trip during constant speed
Description When the inverter output current reaches or exceeds approximately 170% (LD rating) / 148% (SLD rating) of
the rated current during constant-speed operation, the protection circuit is activated and the inverter trips.
Check point • Check for sudden load change.
• Check for output short-circuit.
• Check if the stall prevention operation level is set too high. Check if the fast-response current limit
operation is disabled.
• Check that the inverter capacity matches with the motor capacity. (PM motor control)
• Check if a start command is given to the inverter while the motor is coasting. (PM motor control)
Corrective action • Keep the load stable.
• Check the wiring to make sure that output short circuit does not occur.
• Lower the stall prevention operation level. Activate the fast-response current limit operation. (Refer to page
257.)
• Choose inverter and motor capacities that match. (PM motor control)
• Input a start command after the motor stops. (PM motor control)
Abbreviation E.OC3 FR-LU08
FR-PU07
OC During Dec
Name Overcurrent trip during deceleration or stop
Description When the inverter output current reaches or exceeds approximately 170% (LD rating) / 148% (SLD rating) of
the rated current during deceleration (other than acceleration or constant speed), the protection circuit is
activated and the inverter trips.
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 inverter capacity matches with the motor capacity. (PM motor control)
• Check if a start command is given to the inverter while the motor is coasting. (PM motor control)
Corrective action • Set the deceleration time longer.
• Check the wiring to make sure that output short circuit does not occur.
• Check the mechanical brake operation.
• Lower the stall prevention operation level. Activate the fast-response current limit operation. (Refer to page
257.)
• Choose inverter and motor capacities that match. (PM motor control)
• Input a start command after the motor stops. (PM motor control)
Abbreviation E.SCF FR-LU08
indication
Fault
Name Output short-circuit fault
Description The inverter output is shut off when an output short-circuit is detected while Pr.521 = "1". When Pr.521 = "0"
(initial value), E.OC1, E.OC2, or E.OC3 appears when an output short-circuit is detected.
Check point Check for output short-circuit.
Corrective action Check the wiring to make sure that any output short circuit does not occur, then turn OFF the control circuit
power to reset the inverter.
Abbreviation E.OV1 FR-LU08
FR-PU07
OV During Acc
Name Regenerative overvoltage trip during acceleration
Description If regenerative power causes the inverter's internal main circuit DC voltage to reach or exceed the specified
value, the protection 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 downward acceleration in vertical lift load)
• Check that the Pr.22 Stall prevention operation level is not set to the no load current or lower.
• Check if the stall prevention operation is frequently activated in an application with a large load inertia.
Corrective action • Set the acceleration time shorter. Use the regeneration avoidance function (Pr.882 to Pr.886). (Refer to
page 559.)
• Set a value larger than the no load current in Pr.22.
•Set Pr.154 Voltage reduction selection during stall prevention operation = "10, 11
". (Refer to page
257.)
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