Mitsubishi Electric FR-D720S SC EC Instruction Manual page 442

Causes and corrective actions
Warnings
When the protective function is activated, the output is not shut off.
Operation Panel
Indication
Name
Description
Check point
Corrective action
Operation Panel
Indication
Name
Description
Check point
Corrective action
7 - 6
OL
Stall prevention (overcurrent)
During When the output current of the inverter exceeds the stall prevention oper-
acceleration ation level (Pr. 22 "Stall prevention operation level", etc.), this function
stops the increase in frequency until the overload 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.
During When the output current of the inverter exceeds the stall prevention oper-
constant- ation level (Pr. 22 "Stall prevention operation level", etc.), this function
speed reduces frequency until the overload current decreases to prevent the
operation inverter from resulting in overcurrent trip. When the overload current has
reduced below stall prevention operation level, this function increases the
frequency up to the set value.
During When the output current of the inverter exceeds the stall prevention oper-
deceleration ation level (Pr. 22 "Stall prevention operation level", etc.), this function
stops the decrease in frequency until the overload 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.
Check that the Pr. 7 "Acceleration time" and Pr. 8 "Deceleration time" settings are not
too small.
Check that the load is not too heavy.
Are there any failure in peripheral devices?
Check that the Pr. 13 "Starting frequency" is not too large.
Check that the Pr. 22 "Stall prevention operation level" is appropriate.
Increase or decrease the Pr. 0 "Torque boost setting" 1% by 1% and check the motor
status. (Refer to section 6.2.1.)
Set a larger value in Pr. 7 "Acceleration time" and Pr. 8 "Deceleration time". (Refer to
section 6.6.1.)
Reduce the load weight.
Try advanced magnetic flux vector control and general-purpose magnetic flux vector
control.
Change the Pr. 14 "Load pattern selection" setting.
Set stall prevention operation current in Pr. 22 "Stall prevention operation level". (The
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". (Operation at OL
occurrence can be selected using Pr. 156.)
oL
Stall prevention (overvoltage)
During
If the regenerative energy of the motor becomes excessive and
deceleration
exceeds the regenerative energy consumption capability, this function
stops the decrease in frequency to prevent over voltage shut-off. As
soon as the regenerative energy has decreased, deceleration resumes.
If the regenerative energy of the motor becomes excessive when
regeneration avoidance function is selected (Pr. 882 = 1), this function
increases the speed to prevent over voltage shut-off. (Refer to
section 6.19.4).
Check for sudden speed reduction.
Check that regeneration avoidance function (Pr. 882, Pr. 883, Pr. 885, Pr. 886) is used.
(Refer to section 6.19.4.)
The deceleration time may change. Increase the deceleration time using Pr. 8 "Decelera-
tion time".
FR-PU04
OL
FR-PU07
FR-PU04
oL
FR-PU07
Troubleshooting