9  Troubleshooting
9.2.2  Troubleshooting of Warnings
9-22
9.2.2 Troubleshooting of Warnings
Refer to the following table to identity the cause of a warning and the action to be taken. Contact your 
Yaskawa representative if the problem cannot be solved by the described corrective action.
Warning Num-
ber: Warning 
Name (Warning 
Description)
Cause Investigative Actions Corrective Actions
A.900: 
Position Error 
Overflow
The servomotor U, V, 
and W wirings is faulty.
Check the servomotor main circuit 
cable connection.
Confirm that there is no contact fault 
in the motor wiring or encoder wiring.
The multi-winding 
drive unit gain is too 
low.
Check the multi-winding drive unit 
gain to see if it is low.
Increase the servo gain by using the 
function such as advanced autotuning.
The frequency of the 
position reference pulse 
is too high.
Reduce the reference pulse frequency, 
and operate the multi-winding drive 
unit.
Reduce the position reference pulse 
frequency or acceleration of position 
reference. Or, reconsider the elec-
tronic gear ratio.
The acceleration of the 
position reference is too 
high.
Reduce the reference acceleration, and 
operate the multi-winding drive unit.
Apply the smoothing function, such as 
using the position reference accelera-
tion/deceleration time constant 
(Pn216).
Setting of the excessive 
position error alarm 
level (Pn520) is low 
against the operating 
condition.
Check the alarm level (Pn520) to see 
if it is set to an appropriate value.
Set the Pn520 to proper value.
A fault occurred in the 
multi-winding drive 
unit.
−
Turn the control power supply OFF 
and ON again. If the alarm still occurs, 
the multi-winding drive unit may be 
faulty. Replace the multi-winding 
drive unit.
A.901: 
Position Error 
Overflow Alarm 
at Servo ON
When the servomotor 
power is ON, the posi-
tion error exceeded the 
parameter setting  
(Pn526
×
Pn528/100).
−
Set Pn200.2 to 0 to clear the number 
of position error while the servomotor 
power is OFF. Or set an appropriate 
value for the excessive position error 
warning level at servo ON (Pn528).
A.910: 
Overload
(Warning before 
alarm A.710 or 
A.720 occurs)
Incorrect wiring or con-
tact fault of servomotor 
and encoder.
Check the wiring.
Confirm that the servomotor and 
encoder are correctly wired.
Operation beyond the 
overload protection 
characteristics.
Check the motor overload characteris-
tics and executed run command.
Reconsider the load conditions and 
operating conditions. Or, increase the 
motor capacity.
Excessive load was 
applied during opera-
tion because the servo-
motor was not driven 
due to mechanical prob-
lems.
Check the executed operation refer-
ence and motor speed.
Remove the mechanical problems.
A fault occurred in the 
multi-winding drive 
unit.
−
The multi-winding drive unit may be 
faulty. Replace the multi-winding 
drive unit.