Troubleshooting In The Speed Control - Mitsubishi Electric 800 Series Instruction Manual

5.6

Troubleshooting in the speed control

PM PM PM
Sensorless Sensorless Sensorless
No. Condition
Motor does not run at
the correct speed.
1 (Command speed
and actual speed
differ.)
The speed does not
2 accelerate to the
command speed.
Motor speed
3
fluctuates.
Hunting (vibration or
acoustic noise)
4
occurs in the motor
or the machine.
Acceleration/
deceleration time is
5
different from the
setting.
Machine movement
6
is unstable.
Rotation ripple
7 occurs during the
low-speed operation.
Parameters referred to
Pr.72 PWM frequency selectionpage 146
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.822 Speed setting filter
Pr.824 Torque control P gain 1 (current loop proportional
110
5. Speed control
5.6 Troubleshooting in the speed control
Possible cause
Speed command from
the controller is different
from the actual speed.
The speed command is
affected by noise.
The command speed
and the speed
recognized by the
inverter are different.
The motor constant
varies due to increase in
the motor temperature.
Torque shortage.
The torque limit is
operating.
Only P (proportional)
control is performed.
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 86
1page 271
gain)page 122
• Check that the speed command sent from the controller is correct. (Take EMC
measures.)
• Lower the setting of Pr.72 PWM frequency selection.
• Adjust bias and gain (Pr.125, Pr.126, C2 to C7) of the speed command again.
Enable the online auto tuning at startup (set Pr.95 (Pr.574) = "1") (under Real
sensorless vector control). (Refer to
To perform the online auto tuning at startup for a lift, use a brake sequence function
for the brake opening timing at a start.
• Raise the torque limit.
(Refer to the torque limit for speed control on
• Increase the capacity.
• Speed deviation occurs under P (proportional) control when the load is heavy.
Select PI control.
• 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 273
Countermeasure
page 315.)
page 100.)
page 271.)
page 100.)
page 100.)