Acceleration/Deceleration Is Not Smooth; Speed Varies During Operation - Mitsubishi Electric FR-E700EX Instruction Manual

5.5.6

Acceleration/deceleration is not smooth

Check
Points
Torque limit function is activated due to a heavy load.
Acceleration/deceleration time is too short.
Parameter
Setting Regeneration avoidance operation is performed
Pr.791 and Pr.792 (Acceleration/deceleration time in low-
speed range) are set.
When any mechanical looseness or load fluctuation
exists, the motor resistance calculated by the drive unit
is inaccurate.
Others Mechanical looseness or load fluctuation
5.5.7

Speed varies during operation

Check
Points
The speed setting signal is affected by EMI.
Input
Signal
Malfunction is occurring due to the undesirable current
generated when the transistor output unit is connected.
Multi-speed command signal is chattering.
Parameter
Hunting occurs by the generated vibration, for example,
Setting when structural rigidity at load side is insufficient.
Possible Cause
Possible Cause
Check first when you have a trouble
Countermeasures
Reduce the load weight.
Set Pr.22 Torque limit level higher according to the load.
(Setting Pr.22 too large may result in frequent
overcurrent trip (E.OC).)
Check the capacities of the drive unit and the motor.
Increase acceleration/deceleration time.
If the speed becomes unstable during regeneration
avoidance operation, decrease the setting of Pr.886
Regeneration avoidance voltage gain.
Check the Pr.791 and Pr.792 (Acceleration/deceleration time
in low-speed range) settings.
Set the wiring resistance value in Pr.658 Wiring resistance.
Adjust machine/equipment so that there is no
mechanical looseness. Eliminate the load fluctuation.
Use Pr.156 Torque limit selection to disable the torque
limit.
Countermeasures
Set filter to the analog input terminal using Pr.74 Input
filter time constant.
Take countermeasures against EMI, such as using
shielded wires for input signal lines.
Use terminal PC (terminal SD when source logic) as a
common terminal to prevent a malfunction caused by
undesirable current.
Take countermeasures to suppress chattering.
Disable automatic control functions, such as
regeneration avoidance function and torque limit
operation.
During the PID control, set smaller values to Pr.129 PID
proportional band and Pr.130 PID integral time.
Lower the control gain, and adjust to increase the
stability.
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