Mitsubishi Electric 800 Series Instruction Manual page 633

Causes and corrective actions
Warning
Output is not shut off when a protective function activates.
Abbreviation
Name
Description
Check point
Corrective action
Abbreviation
Name
Description
Check point
Corrective action
632
PROTECTIVE FUNCTIONS
OL
Stall prevention (overcurrent)
• When the output current of the inverter increases, the stall prevention (overcurrent) function activates.
• The following section explains about the stall prevention (overcurrent) function.
When the output current (output torque under Real sensorless vector control or vector
control) of the inverter exceeds the stall prevention level (Pr.22 Stall prevention
During operation level, etc.), this function stops the increase in frequency until the overload
acceleration current decreases to prevent the inverter from resulting in overcurrent trip. When the
overload current has reduced below stall prevention operation level, this function
increases the frequency again.
When the output current (output torque under Real sensorless vector control or vector
control) of the inverter exceeds the stall prevention level (Pr.22 Stall prevention
During
operation level, etc.), this function reduces frequency until the overload current
constant-speed
decreases to prevent the inverter from resulting in overcurrent trip. When the overload
operation
current has reduced below stall prevention operation level, this function increases the
frequency up to the set value.
When the output current (output torque under Real sensorless vector control or vector
control) of the inverter exceeds the stall prevention level (Pr.22 Stall prevention
During operation level, etc.), this function stops the decrease in frequency until the overload
deceleration current decreases to prevent the inverter from resulting in overcurrent trip. When the
overload current has decreased below stall prevention operation level, this function
decreases the frequency again.
• Check that the Pr.0 Torque boost setting is not too large.
• The Pr.7 Acceleration time and Pr.8 Deceleration time settings may be too short.
• Check that the load is not too heavy.
• Check for any failures in peripheral devices.
• Check that the Pr.13 Starting frequency is not too large.
• Check that Pr.22 Stall prevention operation level is appropriate.
• Gradually increase or decrease the Pr.0 setting by 1% at a time and check the motor status. (Refer to
page 589.)
• Set a larger value in Pr.7 Acceleration time and Pr.8 Deceleration time. (Refer to
• Reduce the load.
• Try Advanced magnetic flux vector control, Real sensorless vector control, or vector control.
• Change the Pr.14 Load pattern selection setting.
• The stall prevention operation current can be set in Pr.22 Stall prevention operation level. (Initial value is
150%.) The acceleration/deceleration time may change. Increase the stall prevention operation level with
Pr.22 Stall prevention operation level, or disable stall prevention with Pr.156 Stall prevention operation
selection. (Use Pr.156 to set either operation continued or not at OL operation.)
oL
Stall prevention (overvoltage)
• When the output voltage of the inverter increases, the stall prevention (overvoltage) function activates.
• The regeneration avoidance function activates due to excessive regenerative power of the motor. (Refer to
page 614.)
• The following section explains the stall prevention (overvoltage) function.
If the regenerative power of the motor becomes excessive to exceed the regenerative
power consumption capability, this function stops decreasing the frequency to prevent
During deceleration
overvoltage trip. As soon as the regenerative power has reduced, deceleration
resumes.
• Check for sudden speed reduction.
• Check if the regeneration avoidance function (Pr.882 to Pr.886) is being used. (Refer to
The deceleration time may change. Increase the deceleration time using Pr.8 Deceleration time.
FR-LU08
OL
FR-PU07
FR-LU08
oL
FR-PU07
page 269.)
page 614.)