Mitsubishi Electric FR-A720-0.4K Instruction Manual page 159

(2) Stall prevention operation signal output and output timing adjustment (OL signal, Pr. 157)
⋅ When the output power 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 power 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
Output immediately
(initial value)
0.1 to 25 Output after the set time (s) has elapsed
9999 Not output
REMARKS
⋅ 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).
CAUTION
· If the frequency has fallen to 0.5Hz by stall prevention operation and remains for 3s, an alarm (E.OLT) appears to shutoff the
inverter output.
· When terminal assignment is changed using Pr. 190 to Pr. 196 (output terminal function selection), the other functions may be
affected. 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)
Pr. 22
When Pr. 23 = 9999
When Pr. 23 = "9999", the stall prevention
operation level is as set in Pr. 22 to 400Hz.
Pr. 66
⋅ 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 60Hz in Pr. 66 and 100% in Pr. 23.
⋅ Formula for stall prevention operation level
Stall prevention operation level in
high frequency range (%)
Pr. 66(Hz) × Pr. 22(%)
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.
Description
Stall prevention operation level
as set in Pr. 23
400Hz
Output frequency (Hz)
Pr. 22 - A
= A + B × [
Pr. 22 - B
, B =
Adjust the output torque of the motor (current)
(overvoltage stall) is executed.
Overload state
(OL operation)
OL output signal
Pr.157 Set time(s)
Setting example (Pr.22=150%, Pr.23=100%, Pr.66=60Hz)
150
90
60
45
30
22.5
0 60 100
Pr. 23 - 100
] × [
]
100
Pr. 66(Hz) × Pr. 22(%)
400Hz
200 300 400
Output frequency (Hz)
4
149