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Fine adjustment of gains for speed control
3
Speed does not rise to
the speed command.
(1) Insufficient torque.
Torque limit is actuated.
(1)-1 Increase the torque limit value.
( Refer to the torque limit of speed
control in the Instruction Manual (basic).)
(1)-2 Insufficient capacity
(2) Only P (proportional) control is
selected.
(2) When the load is heavy, speed deviation will
occur under P (proportional) control. Select PI
control.
4
Motor speed is
unstable.
(1) The speed command varies. (1)-1 Check that a correct speed command comes
from the command device. (Take measures
against noises.)
(1)-2 Decrease the PWM carrier frequency in Pr.
72.
(1)-3 Increase the speed setting filter in Pr. 822.
(2) Insufficient torque. (2)-1 Increase the torque limit value.
( Refer to the torque limit of speed
control in the Instruction Manual (basic).)
(2)-2 Return the excitation ratio in Pr. 854 to the
factory setting (100%).
(3) The speed control gains do not
match the machine.
(mechanical resonance)
(3)-1 Perform easy gain tuning.
(3)-2 Adjust Pr. 820 and Pr. 821. (Refer to gain
adjustment.)
(3)-3 Perform speed feed forward control and
model adaptive speed control.
5
Motor or machine hunts
(vibration/noise is
produced).
(1)The speed control gain is high. (1)-1 Perform easy gain tuning.
(1)-2 Decrease Pr. 820 and increase Pr. 821.
(1)-3 Perform speed feed forward control and
model adaptive speed control.
(2) High torque control gain. (2) Decrease Pr. 824. (Refer to page 53.)
(3) Motor wiring and encoder wiring
are not correct.
(3) Check wiring.
Check Pr. 852 setting for the encoder rotation
direction.
6
Acceleration/
deceleration time does
not match the setting.
(1) Insufficient torque. (1)-1 Increase the torque limit value.
( Refer to the torque limit of speed
control in the Instruction Manual (basic).)
(1)-2 Return the excitation ratio in Pr. 854 to the
factory setting.
(1)-3 Perform speed feed forward control.
(2) Large load inertia. (2) Set the acceleration/deceleration time that
meets the load.
7
Machine operation is
unstable
(1) The speed control gains do not
match the machine.
(1)-1 Perform easy gain tuning.
(1)-2 Adjust Pr. 820 and Pr. 821. (Refer to page 46.)
(1)-3 Perform speed feed forward control and
model adaptive speed control.
(2) Slow response because of
improper acceleration/
deceleration time of the inverter.
(2) Change the acceleration/deceleration time to
an optimum value.
8
Speed fluctuates at low
speed.
(1) Adverse effect of high carrier
frequency.
(1) Decrease the PWM carrier frequency in Pr. 72.
(2) Adverse effect of weak excitation. (2) Return the excitation ratio in Pr. 854 to the factory
setting
.
(3) Low speed control gain. (3) Increase Pr. 820 "speed control P gain".
Related parameter reference pages
• Pr. 71 "applied motor" (Refer to page 111.)
• Pr. 72 "PWM frequency selection" (Refer to page 112.)
• Pr. 800 "control system selection" (Refer to page 169.)
• Pr. 820 "speed control P gain 1" (Refer to page 175.)
• Pr. 821 "speed control integral time 1" (Refer to page 175.)
• Pr. 822 "speed setting filter 1" (Refer to page 175.)
• Pr. 851 "number of encoder pulses" (Refer to the Instruction Manual (basic).)
• Pr. 854 "excitation ratio" (Refer to page 181.)
• Pr. 902 "speed setting terminal 2 bias" (Refer to page 190.)
• Pr. 903 "speed setting terminal 2 gain" (Refer to page 190.)
• Pr. 917 "terminal 1 bias (speed)" (Refer to page 190.)
• Pr. 918 "terminal 1 gain (speed)" (Refer to page 190.)
Phenomenon Cause Corrective Action