YASKAWA SGD7S Product Manual page 499

12.2 Alarm Displays
12.2.2 Troubleshooting Alarms
Alarm Number:
Alarm Name
A.C50:
Polarity Detec-
tion Failure
12-30
Possible Cause
Check the linear
The parameter set- encoder specifications
tings are not correct. and feedback signal
status.
Check to make sure
that the frame grounds
of the Serial Converter
Unit and Servomotor
are connected 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
supply.
And, confirm that the
shield is properly pro-
cessed on the Linear
Encoder Cable. Check
to see if the detection
reference is repeatedly
output in one direction.
An external force was
applied to the Moving –
Coil of the motor.
Check the linear
The linear encoder encoder scale pitch to
resolution is too low. see if it is 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.
Correction Reference
page 5-19,
page 5-25
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Continued on next page.