5 Troubleshooting
 
5
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During Startup Fault Symptom Cause Conrming Methods
Input speed 
reference
Servo motor 
rotates in reverse 
direction.
Speed reference 
(H0B-01) is 
negative.
1. When AI is selected to input speed reference, check 
whether polarity of input signal is reverse.
2. When digital setting is used to set speed reference, 
check whether H06-03 (keypad setting value of speed 
reference) is smaller than 0.
3. When multi-speed is used to set speed reference, 
check whether speed references in group H12 are 
positive or negative.
4. When serial comms. is used to set speed reference, 
check whether H31-09 (speed reference set via 
communication) is smaller than 0.
When jog speed reference is used to set speed 
reference, check value of H06-04 (jog speed setting 
value). Then check whether effective logic of DI 
functions FunIN.18: JOGCMD+ (forward jog) and 
FunIN.19: JOGCMD- (reverse jog) matches the 
predicted rotating direction.
Check whether DI function FunIN.26: SpdDirSel 
(speed reference direction) has been allocated and 
whether logic of corresponding DI is valid.
Check whether H02-02 (rotation direction selection) is 
set correctly.
Servo motor can rotate after preceding fault is removed.
Servo motor 
jitters at low 
speed.
Motor speed is not 
steady.
The gain is set 
unreasonably.
Perform automatic gain tuning.
Motor shaft 
vibrates left and 
right.
The load inertia 
ratio (H08-15) is 
too large.
If servo motor can run safely, perform inertia auto-
tuning and perform automatic gain tuning.