Mitsubishi Electric 800 Series Instruction Manual page 158

5.3.3 Troubleshooting in the speed control
PM PM PM
No. Condition
1 Motor does not run at
the correct speed.
(Command speed and
actual speed differ.)
2 The speed does not
accelerate to the
command speed.
3 Motor speed
fluctuates.
4 Hunting (vibration or
acoustic noise) occurs
in the motor or the
machine.
5 Acceleration/
deceleration time is
different from the
setting.
6 Machine movement is
unstable.
7 Rotation ripple occurs
during the low-speed
operation.
Parameters referred to
Pr.3 Base frequency, Pr.19 Base frequency voltage
Pr.72 PWM frequency selection
Pr.80 Motor capacity, Pr.81 Number of motor poles
Pr.125 Terminal 2 frequency setting gain frequency, Pr.126 Terminal 4 frequency setting gain frequency
Pr.822 Speed setting filter 1
Cause
Speed command from the • Check that the speed command sent from the controller is correct. (Take
controller is different from
the actual speed.
• Set Pr.72 PWM frequency selection lower.
The speed command is
affected by noise.
The command speed and • Adjust the bias and gain (Pr.125, Pr.126, Pr.902 to Pr.905, Pr.917,
the speed recognized by the
inverter are different.
Torque shortage. • Raise the stall prevention operation level.
The stall prevention
• (Refer to
operation level is operating.
• Increase the capacity.
Only P (proportional) control • Speed deviation occurs under P (proportional) control when the load is
is performed.
Speed command varies. • Check that the speed command sent from the controller is correct. (Take
• Set Pr.72 lower.
• Set Pr.822 Speed setting filter 1 higher.
Torque shortage. • Raise the stall prevention operation level.
• (Refer to
Speed control gain is not • Adjust Pr.820 Speed control P gain 1 and Pr.821 Speed control integral
suitable for the machine.
(Resonance occurs.)
Speed control gain is too • Set Pr.820 lower and Pr.821 higher.
high.
Torque control gain is too • Set Pr.824 Torque control P gain 1 (current loop proportional gain)
high.
Motor wiring is incorrect. • Check the wiring.
Torque shortage. • Raise the stall prevention operation level.
• (Refer to
Load inertia is too high. • Set acceleration/deceleration time suitable for the load.
Speed control gain is not • Adjust Pr.820 and Pr.821.
suitable for the machine.
Response is slow because • Set the optimum acceleration/deceleration time.
of the inverter's
acceleration/deceleration
time setting.
High carrier frequency is • Set Pr.72 lower.
affecting the motor rotation.
Speed control gain is too • Set Pr.820 higher.
low.
page 539
page 179
page 145
page 326
Countermeasure
EMC measures.)
Pr.918) of the speed command again.
page 257.)
heavy. Select PI control.
EMC measures.)
page 257.)
time 1.
lower.
page 257.)
5.3 Speed control under PM motor control
(page 326)
page 328
5. PARAMETERS
3
4
5
5
5
6
7
8
9
10
157