Mitsubishi Electric FR-A720-0.4K Instruction Manual page 122

Phenomenon
(1) The speed command varies.
Motor speed is (2) Insufficient torque.
4
unstable.
(3) The speed control gains do not
(1) The speed control gain is high.
Motor or machine
5 hunts (vibration/
noise is produced).
(2) The torque control gain is high.
(3) The motor wiring is wrong.
(1) Insufficient torque.
Acceleration/
deceleration time
6
does not match the
setting.
(2) Large load inertia.
(1) The speed control gains do not
Machine operation is
7
unstable
(2) Slow response because of
(1) Adverse effect of high carrier
Speed fluctuates at
8
low speed.
(2) Low speed control gain.
Cause
match the machine. (mechanical
resonance)
match the machine.
improper acceleration/
deceleration time of the inverter.
frequency.
Speed control by Real sensorless
vector control, vector control
Countermeasures
(1) -1 Check that a correct speed command comes from the
command device. (Take measures against noises.)
(1) -2 Decrease Pr. 72 PWM frequency selection.
(1) -3 Increase Pr. 822 Speed setting filter 1. (Refer to page 292)
(2) Increase the torque limit value.
(Refer to torque limit of speed control on page 100)
(3) -1 Perform easy gain tuning. (Refer to page 106)
(3) -2 Adjust Pr. 820, Pr. 821. (Refer to page 108)
(3) -3 Perform speed feed forward/model adaptive speed
control.
(1) -1 Perform easy gain tuning. (Refer to page 106)
(1) -2 Decrease Pr. 820 and increase Pr. 821.
(1) -3 Perform speed feed forward control and model adaptive
speed control.
(2) Decrease the Pr. 824 value. (Refer to page 130)
(3) Check the wiring
(1) -1 Increase the torque limit value.
(Refer to torque limit of speed control on page 100)
(1) -2 Perform speed feed forward control.
(2) Set the acceleration/deceleration time that meets the load.
(1) -1 Perform easy gain tuning. (Refer to page 106)
(1) -2 Adjust Pr. 820, Pr. 821. (Refer to page 108)
(1) -3 Perform speed feed forward control and model adaptive
speed control.
(2) Change the acceleration/deceleration time to an optimum
value.
(1) Decrease Pr. 72 PWM frequency selection.
(2) Increase Pr. 820 Speed control P gain 1.
4
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