Mitsubishi Electric F700 Instruction Manual page 64

(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 region (Pr.22, Pr.23, Pr.66)
Pr.22
When Pr.23=9999
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 region. This function is effective for performing operation up to the high-speed range on a
centrifugal separator etc. Normally, set 60Hz to Pr. 66 and 100% to Pr. 23.
⋅ Formula for stall prevention operation level
Stall prevention operation level (%)= A + B × [
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
Pr.23
400Hz
Output frequency (Hz)
, 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 = 120%
Pr.23 = 100%
Pr.66 = 60Hz
120
90
60
36
24
18
0 80 100 200
Pr.22 - A Pr.23 - 100
] × [
Pr.22 - B 100
Pr.66(Hz) × Pr.22(%)
400Hz
300 400
Output frequency (Hz)
]
57
3