YASKAWA SGD7S-***A20****F62 Series Product Manual page 100

5.3 Troubleshooting Alarms
Alarm Number:
Alarm Name
A.C50:
Polarity Detec-
tion Failure
5-26
Possible Cause
Check the linear encoder
The parameter set-
specifications and feed-
tings are not correct.
back signal status.
Check to make sure that
the frame grounds of the
Serial Converter Unit and
Servomotor are con-
nected to the FG terminal
on the SERVOPACK and
that the FG terminal on
the SERVOPACK is con-
There is noise on the nected to the frame
scale signal. ground on the power sup-
ply.
And, confirm that the
shield is properly pro-
cessed on the Linear
Encoder Cable. Check to
see if the detection refer-
ence is repeatedly output
in one direction.
An external force was
applied to the Moving –
Coil of the motor.
Check the linear encoder
The linear encoder
scale pitch to see if it is
resolution is too low.
within 100 μm.
Confirmation
The settings of Pn282
(Linear Encoder Scale
Pitch) and Pn080 =
n.X (Motor Phase
Sequence Selection) may
not match the installa-
tion. Set the parameters
to correct values.
Implement appropriate
countermeasures against
noise for the Linear
Encoder Cable.
The polarity cannot be
properly detected if the
detection reference is 0
and the speed feedback
is not 0 because of an
external force, such as
cable tension, applied to
the Moving Coil. Imple-
ment measures to reduce
the external force so that
the speed feedback goes
to 0. If the external force
cannot be reduced,
increase the setting of
Pn481 (Polarity Detection
Speed Loop Gain).
If the linear encoder scale
pitch is 100 μm or higher,
the SERVOPACK cannot
detect the correct speed
feedback. Use a linear
encoder scale pitch with
higher resolution. (We rec-
ommend a pitch of 40 μm
or less.) Or, increase the
setting of Pn485 (Polarity
Detection Reference
Speed). However,
increasing the setting of
Pn485 will increase the
Servomotor movement
range that is required for
polarity detection.
Continued from previous page.
Refer-
Correction
ence
*1
–
–
–
Continued on next page.