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Protective functions (Pr. 870 to Pr. 874)
PARAMETERS
3
3.37.2 Speed limit (Pr. 873 )
3.37.3 Stop by OLT level prevention (Pr. 874 )
(2) V/F control
If the stall prevention function is activated and the output frequency is kept reduced to 0Hz for 3s, OLT will
cause an alarm stop.
In this case, this function is activated regardless of Pr. 874.
(3) Torque control
This alarm is not activated.
This function prevents the motor from
overrunning when the setting of
number of encoder pulses and the
actual number differ. When the setting
of number of encoder pulses is smaller
than the actual number, the motor may
increase its speed. To prevent this,
restrict the output speed with the
synchronous speed obtained by
adding the set speed and Pr. 873
setting. (*)
Parameter Name Factory Setting Setting Range Remarks
873 Speed limit 600r/min 0 to 3600r/min Extended mode
CAUTION
* When the setting of number of the encoder pulses is smaller than the actual number, selecting
automatic restart after instantaneous power failure function (set a value other than "9999" in Pr. 57)
restrict the output speed with the synchronous speed obtained by adding the maximum speed (Pr. 1)
and Pr. 873 setting.
This function can make an alarm stop if the torque limit is activated to stall the motor.
Parameter Name Factory Setting Setting Range Remarks
874 OLT level setting 150% 0 to 200% Extended mode
(1) Speed control, position control
The motor stalls if the torque limit is
activated under a high load applied
during speed control or position control.
At this time, if the motor speed is lower
than the speed set in Pr. 865 (low speed
detection) and also the output torque
exceeds the level set in Pr. 874 for 3s, it
is regarded as a stop effected by stall
prevention and E. OLT is output,
resulting in an alarm stop.
Related parameters
• Low speed detection ⇒ Pr. 865 "low speed detection" (Refer to page 182.)
speed
Set speed Pr. 873 setting
Pr. 873 setting
Set speed
Actual speed
during normal
operation
A
ctual rotation
speed at alarm
occurrence
speed position
Output torque
Motor speed
Start signal (STF)
Alarm contact
Pr. 874
Torque limit
Pr. 865
3s
If torque limit is activated and speed falls below
Pr. 865 setting, OLT alarm does not occur when output
torque at this time is lower than Pr. 874.
Time
Time
Torque