(2) Stall prevention operation signal output and output timing adjustment (OL signal, Pr. 157)
When the output current exceeds the stall prevention operation level and stall prevention is activated, the stall
prevention operation signal (OL signal) turns on for longer than 100ms. When the output current falls to or below
the stall prevention operation level, the output signal turns off.
Use Pr. 157 OL signal output timer to set whether the OL signal is output immediately or after a preset period of time.
This operation is also performed when the regeneration avoidance function
Pr. 157 Setting
0.1 to 25
Output after the set time (s) has elapsed.
The OL signal is assigned to the terminal OL in the initial setting. The OL signal can also be assigned to the other terminal by
setting "3 (positive logic) or 103 (negative logic)" to any of Pr. 190 to Pr. 196 (output terminal function selection).
· If the frequency has fallen to 0.5Hz by stall prevention operation and remains for 3s, a fault (E.OLT) appears to shutoff the
· Changing the terminal assignment using Pr. 190 to Pr. 196 (output terminal function selection) may affect the other functions.
Please make setting after confirming the function of each terminal.
(3) Setting of stall prevention operation in high frequency range (Pr. 22, Pr. 23, Pr. 66)
When Pr. 23 = 9999
When Pr. 23 = "9999", the stall prevention
operation level is as set in Pr. 22 to 400Hz.
During high-speed operation above the rated motor frequency, acceleration may not be made because the motor
current does not increase. If operation is performed in a high frequency range, the current at motor lockup
becomes smaller than the rated output current of the inverter, and the protective function (OL) is not executed if the
motor is at a stop.
To improve the operating characteristics of the motor in this case, the stall prevention level can be reduced in the
high frequency range. This function is effective for performing operation up to the high-speed range on a centrifugal
separator etc. Normally, set 50Hz in Pr. 66 and 100% in Pr. 23.
Formula for stall prevention operation level
Stall prevention operation level in high
frequency range (%)
However, A =
Output frequency (H)
When Pr. 23 Stall prevention operation level compensation factor at double speed = "9999" (initial value), the stall
prevention operation level is kept constant at the Pr. 22 setting up to 400Hz.
Stall prevention operation level
as set in Pr. 23
Output frequency (Hz)
= A + B
, B =
Adjustment of the output torque (current) of the motor
(overvoltage stall) is executed.
OL output signal
Pr.157 Set time(s)
Pr. 22 - A
Pr. 23 - 100
Pr. 22 - B
Pr.22 = 110%
Pr.23 = 100%
Pr.66 = 50Hz
Output frequency (Hz)