3-8
Overspeeding
• An alarm will go off if the rotation speed of the motor is abnormal, as in the following cases:
The rotation speed has exceeded the maximum allowable rotation speed.
The rotation signal is not returned from the motor in response to a command from the Servo Driver.
A command is input for the motor to run at a speed exceeding the maximum allowable rotation speed.
Alarm Indication
U Series: A. 51, A. 52, A. C1, A. C2
H Series: E22
M Series: A. L-16, A. L-19, A. L-20
R Series: O. RUN
Probable cause Item to check Countermeasure
Abnormal speed command input • The voltage of the speed com-
mand input (analog input) is
higher than the voltage corre-
sponding to the maximum allow-
able rotation speed.
• The frequency of the command
pulse input (pulse-train input) is
higher than the frequency corre-
sponding to the maximum allow-
able rotation speed.
• Decrease the command speed.
Parameter setting mistake.
• The speed command scale ex-
ceeds the maximum allowable
rotation speed. (Applicable to
analog input.)
• Fix the speed command scale
setting.
• The encoder dividing ratio set-
ting for pulse output is too small.
(Applicable to analog input.)
• Fix the number of output pulses.
• The electronic gear ratio is too
large. (Applicable to pulse-train
input.)
• Fix the electronic gear ratio.
Overspeeding due to
overshooting.
• Overshooting exceeding the
maximum allowable rotation
speed results at the time of ac-
celeration.
(Use the speed monitor.)
• Adjust the gain and suppress the
overshooting as much as pos-
sible.
Abnormal encoder cable
Abnormal resolver cable
• The cable is disconnected.
• The cable is short-circuited.
* Check the resistance of the
cable alone.
• Replace the encoder cable.
• Replace the resolver cable.
Power cable disconnection. • The power cable is discon-
nected.
* Check the resistance of the
cable alone.
• Replace the power cable.
Abnormal motor. • Motor phases are open.
*Check the resistance of the
motor alone.
• Replace the motor.
Signal errors caused by noise. • None of the above items applies.
• The frequency and conditions of
error are indefinite.
• Take countermeasures against
noise. Refer to Chapter 4 Coun-
termeasures Against Noise.
Servo Driver Errors Chapter 3
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