Mitsubishi Electric FR-A700 Instruction Manual page 288

Speed control by real sensorless vector control, vector control
Speed limit (Pr. 873)
● 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 frequency with frequency
(obtained by adding the set frequency and Pr. 873 ).
Fig. 6-23: Speed limit
If automatic restart after instantaneous power failure (Pr. 57 ≠ 9999) is selected when the
NOTES
setting of number of encoder pulses is smaller than the actual number, the output speed is
limited with the synchronous speed obtained by adding the maximum setting (Pr. 1) and
Pr. 873 setting.
When speed limit function is activated due to regenerative torque limit, output torque may
suddenly decrease. In addition, output phase error (E.LF) may occur when speed limit func-
tion is activated during pre-excitation. When the setting of number of encoder pulses are
correct, it is recommended to set a mamimum value (120Hz) in Pr. 873.
6 - 108
Set speed + Pr. 873 value
Actual speed at
error occurrence
Parameter
Value of Pr. 873
Set speed
Speed during
normal operation
I001519E