Mitsubishi Electric FR-A720-0.4K Instruction Manual page 121

Speed control by Real sensorless vector
control, vector control
(8) Troubleshooting (speed)
Phenomenon
Motor does not
1 rotate.
(Vector control)
Motor does not run
at correct speed.
2 (Speed command
does not match
actual speed)
Speed does not rise
3 to the speed
command.
110
Cause
(1) The motor wiring is wrong
(2) Encoder specification selection
switch (FR-A7AP/FR-A7AL
(option)) is wrong.
(3) The encoder wiring is wrong.
(4) The Pr. 369 Number of encoder
pulses setting and the number of
encoder used are different.
(5) Encoder power specifications
are wrong. Or, power is not input.
(1) The speed command from the
command device is incorrect.
The speed command is
compounded with noise.
(2) The speed command value
does not match the inverter-
recognized value.
(3) The number of encoder pulses
setting is incorrect.
(1) Insufficient torque.
Torque limit is actuated.
(2) Only P (proportional) control is
selected.
Countermeasures
(1) Wiring check
Select V/F control (set "9999" in Pr. 80 or Pr. 81 ) and check
the rotation direction of the motor.
For the SF-V5RU (1500r/min series), set "170V(340V)" for
3.7kW or lower and "160V(320V)" for more in Pr. 19 Base
frequency voltage, and set "50Hz" in Pr. 3 Base frequency.
When the forward rotation signal is input, the
motor running in the counterclockwise direction
as viewed from the motor shaft is normal. (If it
runs in the clockwise direction, the phase
sequence of the inverter secondary side wiring
is incorrect.)
(2) Check the encoder specifications.
Check the encoder specifications selection switch (FR-
A7AP/FR-A7AL (option)) of differential/complementary
(3) Check that FWD is displayed when running the motor in the
counter-clockwise direction from outside during a stop of
the inverter with vector control setting.
If REV is displayed, the encoder phase sequence is wrong.
Check that the wiring is correct, and set the rotation
direction in Pr.359 Encoder rotation direction according to the
motor specification.
Relationship between the Motor and
Pr. 359
Setting
0
Encoder
Clockwise direction as viewed
from A is forward rotation
1
(Initial
Encoder
value)
Counter clockwise direction as
viewed from A is forward rotation
(4) The motor will not run if the parameter setting is smaller
than the number of encoder pulses used. Set the Pr. 369
Number of encoder pulses correctly.
(5) Check the power specifications (5V/12V/15V/24V) of
encoder and input the external power supply. Make the
voltage of the external power supply the same as the
encoder output voltage, and connect the external power
supply between PG and SD.
(1) Check that a correct speed command comes from the
command device.
Decrease Pr. 72 PWM frequency selection.
(2) Readjust speed command bias/gain Pr. 125, Pr. 126, C2 to C7
and C12 to C15.
(3) Check the setting of Pr. 369 Number of encoder pulses. (vector
control)
(1) -1 Increase the torque limit value.
(Refer to torque limit of speed control on page 100 )
(1) -2 Insufficient capacity
(2) When the load is heavy, speed deviation will occur under P
(proportional) control. Select PI control.
Encoder
CW
A
Set the
rotation
direction
according to
the motor
CCW
A
specification.