Mitsubishi Electric 800 Series Instruction Manual (Function page 299

 Adjusting the stall prevention operation signal and output timing (OL
signal, Pr.157)
• If the output current exceeds the stall prevention operation level and stall prevention is activated, or the fast-response
current limit is enabled, Overload warning (OL) signal turns ON for 100 ms or more. The output signal turns OFF when the
output current falls to the stall prevention operation level or less.
• 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.
• This function also operates during regeneration avoidance operation ("OLV" (overvoltage stall)).
• For the OL signal, set "3" (positive logic) or "103" (negative logic) in any parameter from Pr.190 to Pr.196 (Output terminal
function selection) to assign the function to the output terminal.
Pr.157 setting
0 (initial value) Output immediately.
0.1 to 25 Output after the set time (s).
9999 Not output.
Overload state
(OL operation)
OL output signal
NOTE
• If the stall prevention operation has lowered the output frequency to 1 Hz and kept the level for 3 seconds, the stall prevention
stop (E.OLT) is activated to shut off the inverter output.
• 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.
 Setting for stall prevention operation in the high-frequency range (Pr.22,
Pr.23, Pr.66)
Always at the Pr.22 level
when Pr.23 = "9999"
Pr.22
Pr.66
• When operating at the rated motor frequency or higher, acceleration may not be made because the motor current does
not increase. Also, when operating in the high-frequency range, the current flowing to the locked motor becomes less than
the rated output current of the inverter. Even if the motor is stopped, the protective function does not operate (OL). In a
case like this, the stall prevention level can be reduced in the high-frequency range to improve the motor's operating
characteristics. This is useful when operating up to the high speed range, such as when using a centrifuge. Normally, set
Pr.66 Stall prevention operation reduction starting frequency to 60 Hz, and Pr.23 Stall prevention operation level
compensation factor at double speed to 100%.
• Calculation formula for stall prevention operation level
Stall prevention operation level (%)
in the high-frequency range
Pr.66 (Hz) × Pr.22 (%)
Where,
A =
Output frequency (Hz)
• When Pr.23 = "9999" (initial value), the stall prevention operation level is constant at the Pr.22 level up to 590 Hz.
298
12. (H) Protective Function Parameters
12.10 Stall prevention operation
Description
Pr.157 Set time(s)
Stall prevention operation level
as set in Pr.23
400Hz
Output frequency (Hz)
Pr.22 - A
= A + B × [
Pr.22 - B
, B =
Setting example (Pr.22 = 150%, Pr.23 = 100%, Pr.66 = 60Hz)
120
Pr.23 - 100
] × [ ]
100
Pr.66 (Hz) × Pr.22 (%)
400 Hz
72
36
24
18
0 60 100 200 300
Output frequency (Hz)
400