Acceleration/Deceleration Is Not Smooth; Speed Varies During Operation - Mitsubishi Electric FR-D720-0.2K-G Instruction Manual

Check first when you have a trouble
5.5.7

Acceleration/deceleration is not smooth

Check
Points
Acceleration/deceleration time is too short.
Stall prevention function is activated due to a heavy
load.
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
The machine is unstable, or the load fluctuates.
5.5.8

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.
The setting of Pr.998 PM parameter initialization (Pr.80
Motor capacity and Pr.81 Number of motor poles) is not
appropriate according to the applied motor.
Offline auto tuning is not performed when driving a
motor other than S-PM geared motor.
Parameter
Setting
Hunting occurs by the generated vibration, for example,
when structural rigidity at load side is insufficient.
268
Possible Cause
Possible Cause
Countermeasures
Increase acceleration/deceleration time.
Reduce the load weight.
Set Pr. 22 Stall prevention operation 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.
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 Stall prevention operation selection to disable
stall prevention operation.
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.
Set Pr.998 (Pr.80 and Pr.81) correctly.
Perform offline auto tuning.
Disable automatic control functions, such as
regeneration avoidance function and stall prevention.
During the PID control, set smaller values to Pr. 129 PID
proportional band and Pr. 130 PID integral time.
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.
Refer
to
Page
97
—
83
—
228
97
82
83
Refer
to
Page
151
38
21
—
73, 105
105
—