Mitsubishi Electric FR-A800 Series Instruction Manual page 254

• When a high load is applied and the torque limit is activated under speed control or position control, the motor stalls. At
this time, if a state where the rotation speed is lower than the value set in Pr.865 Low speed detection and the output
torque exceeds the level set in Pr.874 OLT level setting continues for 3 seconds, Stall prevention stop (E.OLT) is
activated and the inverter output is shut off.
NOTE
• Under V/F control or Advanced magnetic flux vector control, if the output frequency drops to 0.5 Hz due to the stall prevention
operation and this state continues for 3 seconds, a fault indication (E.OLT) appears, and the inverter output is shut off. This
operation is activated regardless of the Pr.874 setting.
• This fault does not occur under torque control.
 Adjusting the signal output under torque limit operation and output
timing (OL signal, Pr.157)
• If the output torque exceeds the torque limit level and the torque limit is activated, the overload warning (OL signal) is turned
ON for 100 ms or longer. When the output torque drops to the torque limit level or lower, the output signal also turns OFF.
• Pr.157 OL signal output timer can be used to set whether to output the OL signal immediately, or whether to output it
after a certain time period has elapsed.
Pr.157 setting
value
0 (initial value)
0.1 to 25
9999
• The OL signal is also output during the regeneration avoidance operation ("
Overload state
(OL operation)
OL output signal
NOTE
• The OL signal is assigned to terminal OL in the initial status. The OL signal can also be assigned to other terminals by setting
"3 (positive logic) or 103 (negative logic)" in any of Pr.190 to Pr.196 (Output terminal function selection).
• Changing the terminal assignment using Pr.190 to Pr.196 (Output terminal function selection) may affect the other
functions. Set parameters after confirming the function of each terminal.
Parameters referred to
Pr.22 Stall prevention operation
Pr.178 to Pr.189 (Input terminal function
Pr.190 to Pr.196 (Output terminal function
Pr.840 Torque bias
Pr.865 Low speed
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Torque
Output torque
Output
frequency
Start signal
(STF)
Fault signal
(ALM)
Description
Output immediately.
Output after the set time (s).
Not output.
Pr.157 Set time(s)
levelpage 431
selection)page 521
selection)page 473
selectionpage 265
detectionpage 484
5.3 Speed control under Real sensorless vector control, vector control, PM sensorless vector control
search engine
Torque limit
Pr.874
Pr.865
3s
E.OLT occurrence
Time
Time
" display (overvoltage stall)).
5. PARAMETERS
1
2
3
4
5
6
7
8
9
10
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