Speed control by real sensorless vector
control, vector control
Prevent the motor from overrunning (Pr. 285, Pr. 853, Pr. 873)
This function prevents the motor from overrunning when the load torque is too large and incorrect number of
encoder is set.
Speed deviation time
Acts as Overspeed detection frequency under encoder feed back operation. (Refer to page 214)
This parameter can be set when the FR-A7AP (option) is mounted.
(1) Speed deviation excessive (Pr. 285, Pr. 853)
When the deviation between the set frequency and actual speed is large, e.g. too large load torque, this function can
cause the inverter to provide a speed deviation excessive alarm (E.OSD) and come to an alarm stop.
(2) Speed limit (Pr. 873)
This function prevents the motor from overrunning when the setting of number of encoder pulses and the actual
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 ).
at error occurrence
⋅ If automatic restart after instantaneous power failure (Pr. 57 ≠ 9999) is selected when the 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 function 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.
Pr. 285 Overspeed detection frequency
0 to 30Hz
0 to 100s
0 to 120Hz
excessive error activated
Set speed + Pr. 873 value
Refer to page
Without speed deviation excessive
If the difference (absolute value) between the
speed command value and actual speed during
speed control under vector control exceeds the
Pr. 285 Excessive speed deviation detection
frequency for more than the time set in Pr. 853
Speed deviation time, speed deviation excessive
occurs and inverter error (E. OSD) appears,
resulting in a stop.
Frequency is limited at the set frequency + Pr. 873.
Value of Pr. 873