Mitsubishi Electric FR-A700 Instruction Manual page 699

Parameter
Feedback gain (Pr. 368)
Set Pr. 368 "Feedback gain" when the rotation is unstable or response is slow.
If the acceleration/deceleration time is long, feedback response becomes slower. In this case,
increase the Pr. 368 setting.
Pr. 368 Setting
Pr. 368 > 1
Pr. 368 < 1
Tab. 6-178: Setting of parameter 368
Overspeed detection (Pr. 285)
If (detection frequency) - (output frequency) > Pr. 285 under encoder feedback control, E.MB1
occurs and the inverter output is stopped to prevent malfunction when the accurate pulse signal
from the encoder can not be detected. Overspeed is not detected when Pr. 285 = "9999".
NOTES
The encoder should be coupled on the same axis with the motor shaft with a speed ratio of 1
to 1 without any mechanical looseness.
During acceleration/deceleration, encoder feedback control is not performed to prevent
unstable phenomenon such as hunting.
Encoder feedback control is performed once output frequency has reached within
[set speed] ± [speed feedback range].
If the following conditions occur during encoder feedback control, the inverter operates at
the frequency within [set speed] ± [speed feedback range] without coming to an alarm stop
nor tracking the motor speed.
The pulse signals are not received from the encoder due to a signal loss, etc.
The accurate pulse signal from the encoder can not be detected due to induction noise, etc.
The motor has been forcibly accelerated (regeneration) or decelerated (motor lock or the
like) by large external force.
For the motor with brake, use the RUN signal (inverter running) to open the brake. (The
brake may not be opened if the FU (output frequency detection) signal is used.)
Do not turn off the external power supply of the encoder during encoder feedback control.
Encoder feedback control functions abnormally.
FR-A700 EC
Description
Although the response becomes faster, overcurrent or unstable rotation is liable to
occur.
Although the response becomes slower, the motor rotation becomes stable.
Special operation
6 - 519