MITSUBISHI ELECTRIC FR-S520 - Manual (Page 78)

69
2
CAUTION
•
* When "Operation not continued for OL signal output" is selected, the "OLT" alarm
code (stopped by stall prevention) is displayed and operation stopped.
(Alarm stop display "
")
•
If the load is heavy, the lift is predetermined, or the acceleration/deceleration time
is short, the stall prevention may be activated and the motor not stopped in the
preset acceleration/deceleration time. Therefore, set optimum values to the Pr. 21
and stall prevention operation level.
•
When the fast-response current limit has been set in Pr. 21 (factory setting),
torque will not be provided at the Pr. 22 setting of 170% or higher. At this time,
make setting so that the fast-response current limit is not activated.
•
In vertical lift applications, make setting so that the fast-response current limit is
not activated. Torque may not be produced, causing a gravity drop.
CAUTION
Always perform test operation.
Stall prevention operation performed during acceleration may increase the
acceleration time.
Stall prevention operation performed during constant speed may cause sudden
speed changes.
Stall prevention operation performed during deceleration may increase the
deceleration time, increasing the deceleration distance.
2
.3.13 Stall prevention
Set the output current level at which the output frequency will be adjusted to
prevent the inverter from stopping due to overcurrent etc.
During high-speed operation above the rated motor frequency, acceleration
may not be made because the motor current does not increase. 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 <50Hz> in Pr. 28 "stall prevention operation reduction
starting frequency" and 100% in Pr. 23.
Parameter Name
Factory
Setting
Setting
Range
Remarks
22
Stall prevention operation
level
150% 0 to 200%

23
Stall prevention operation
level compensation factor
at double speed
- - -
0 to
200%, - - -
- - -: Pr. 22
equally
28
Stall prevention operation
reduction starting frequency 60Hz
<50Hz>
0 to
120Hz

Setting is
enabled
when
Pr. 30 = "1".