Mitsubishi Electric FR-A720-0.4K Instruction Manual page 148

Position control by vector control
(3) Troubleshooting
Phenomenon
1 Motor does not rotate
2 Position shift occurs.
3 Motor or machine hunts.
Machine operation is
4
unstable
♦Parameters referred to♦
Pr. 7 Acceleration time Refer to page 168
Pr. 8 Deceleration time Refer to page 168
Pr. 72 PWM frequency selection
Pr. 800 Control method selection
Pr. 802 Pre-excitation selection
Pr. 819 Easy gain tuning selection
Pr. 820 Speed control P gain 1
Pr. 821 Speed control integral time 1
138
Cause
(1) The phase sequence of the
motor or encoder wiring is
wrong.
(2) The control mode selection Pr.
800 setting is improper.
(3) The servo on signal or stroke
end signal (STF, STR) is not
input.
(4) Command pulse, position pulse
sign (NP) are not correctly
input.
(5) Pr. 419 Position command source
selection setting is not correct.
(6) When "0" is set in Pr. 419
Position command source
selection, the settings of position
feed amount in Pr. 465 to Pr. 494
are not correct.
(1) The command pulses are not
input correctly.
(2) The command is affected by
noise. Or the encoder feedback
is compounded with noise.
(1) The position loop gain is high.
(2) The position loop gain is high.
(1) The acceleration/deceleration
time setting has adverse effect.
Refer to page 271
Refer to page 91
Refer to page 194
Refer to page 103
Refer to page 103
Refer to page 103
Countermeasures
(1) Check the wiring. (Refer to page 39 )
(2) Check the Pr. 800 setting. (Refer to page 91 )
(3) Check that the signals are input normally.
(4)-1 Check that the command pulses are input normally.
(Check the cumulative command pulse value in Pr.
430)
(4)-2 Check the command pulse form and command
pulse selection, Pr. 428, setting.
(4)-3 Check that the position pulse sign (NP) is assigned
to the input terminal. (inverter pulse input)
(5) Check the position command source selection in Pr.
419.
(6) Check the position feed amount in Pr. 465 to Pr. 494 .
(1)-1 Check the command pulse form and command
pulse selection, Pr. 428 setting.
(1)-2 Check that the command pulses are input normally.
(Check the cumulative command pulse value in Pr.
430 )
(1)-3 Check that the position pulse sign (NP) is assigned
to the input terminal. (inverter pulse input)
(2)-1 Decrease the Pr. 72 PWM frequency selection value.
(2)-2 Change the earthing (grounding) point of shielded
wire. Or leave the cable suspended.
(1) Decrease the Pr. 422 value.
(2)-1 Perform easy gain tuning.
(2)-2 Decrease Pr. 820 and increase Pr. 821 .
(1) Decrease Pr. 7 and Pr. 8 .