Mitsubishi Electric 800 Series Instruction Manual (Function page 141

No. Condition
Motor speed
4
fluctuates.
Hunting (vibration or
acoustic noise)
5
occurs in the motor
or the machine.
Acceleration/
deceleration time is
6
different from the
setting.
Machine movement
7
is unstable.
Rotation ripple
8 occurs during the
low-speed operation.
Parameters referred to
Pr.72 PWM frequency selectionpage 221
Pr.80 Motor capacity, Pr.81 Number of motor
Pr.125 Terminal 2 frequency setting gain frequency, Pr.126 Terminal 4 frequency setting gain
Pr.359 Encoder rotation direction, Pr.369 Number of encoder
Pr.822 Speed setting filter
Pr.824 Torque control P gain 1 (current loop proportional
140
5. Speed Control
5.9 Troubleshooting in the speed control
Possible cause
Speed command varies.
Torque shortage.
Speed control gain is not
suitable for the machine.
(Resonance occurs.)
Speed control gain is too
high.
Torque control gain is
too high.
Motor wiring is incorrect. • Check the wiring.
Torque shortage.
Load inertia is too high.
Speed control gain is not
suitable for the machine.
Response is slow
because of the inverter's
acceleration/
deceleration time
setting.
High carrier frequency is
affecting the motor
rotation.
Speed control gain is too
low.
polespage 104
1page 356
gain)page 155
• Check that the speed command sent from the controller is correct. (Take EMC
measures.)
• Set Pr.72 lower.
• Set Pr.822 Speed setting filter 1 higher. (Refer to
• Raise the torque limit.
(Refer to the torque limit for speed control on
• Adjust Pr.820 Speed control P gain 1 and Pr.821 Speed control integral time
1.
• Set Pr.820 lower and Pr.821 higher.
• Set Pr.824 Torque control P gain 1 (current loop proportional gain) lower.
• Raise the torque limit.
(Refer to the torque limit for speed control on
• Set acceleration/deceleration time suitable for the load.
• Adjust Pr.820 and Pr.821.
• Set the optimum acceleration/deceleration time.
• Set Pr.72 lower.
• Set Pr.820 higher.
frequencypage 358
pulsespage 405
Countermeasure
page 356.)
page 122.)
page 122.)