Mitsubishi Electric 800 Series Instruction Manual page 181

Speed control under Real sensorless vector control, vector control, PM sensorless vector
control
NOTE
• When the automatic restart after instantaneous power failure function is selected (Pr.57 Restart coasting time "9999") and
the setting value for the number of encoder pulses is lower than the actual number of pulses, the output speed is limited with
the synchronous speed of the value of Pr.1 Maximum frequency + Pr.873.
• When a regenerative driving torque limit is applied and the speed limit function activates, the output torque may drop
suddenly. Also, when the speed limit function activates during pre-excitation operation, output phase loss (E.LF) may occur.
If the setting for the number of encoder pulses is confirmed as correct, it is recommended that Pr.873 be set to the maximum
value (400 Hz).
• Even if the set frequency is lowered after inverter operation, the speed limit value is not lowered. During deceleration, the
speed is limited at frequency command value + Pr.873.
Deceleration check (Pr.690)
• When performing a deceleration stop on the motor, accidental acceleration can cause the inverter to trip. This can prevent
a malfunction due to an incorrect encoder pulse setting, when the motor has stopped.
• When the difference between the actual motor speed and the speed command value exceeds 2 Hz after the start
signal (STF, STR) is OFF, the deceleration check will start.
• If the motor has not decelerated in the time period between the start signal (STF, STR) OFF and the Pr.690 setting, the
protective function (E.OSD) is activated to trip the inverter.
NOTE
• The deceleration check is enabled in the speed control of the vector control.
• If the protective function (E.OSD) operates due to deceleration check, check whether the Pr.369 (Pr.851) Number of
encoder pulses setting is correct.
Parameters referred to ???????
Pr.285 Overspeed detection frequency
Pr.369 Number of encoder pulses, Pr.851 Control terminal option-Number of encoder pulses
180
PARAMETERS
Motor speed
Pr.690
Start signal
ON
(STF, STR)
Fault output
(ALM)
page 619
Motor coasting
Time
ON
E.OSD
page 64