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4 APPLICABLE FUNCTIONS
4.12 Speed limit [A]
4.12
Speed limit [A]
During the torque mode, this function serves to limit the servo motor speed in order not to generate excessive speed.
• Speed limit can be used only in the torque mode.
Precautions
• When the servo motor speed reaches the speed limit value, torque control may become unstable.
Setting method
Speed limit value and servo motor speed
The speed is limited to the values set with [Pr. PC05 Internal speed 1] to [Pr. PC11 Internal speed 7] or the value set in the
applied voltage of VLA (Analog speed limit). The relation between the applied voltage in VLA (Analog speed limit) and the
servo motor speed is shown below. The speed limit direction and torque command direction are the same direction. There is
no speed limit in the torque command direction and the opposite direction.
The following table indicates the limit direction according to the combination of RS1 (Forward rotation selection) and RS2
(Reverse rotation selection).
*1 0: off, 1: on
Input device
TC (Analog torque command)
Speed limit direction
RS1
RS2
VLA (Analog speed limit)
Internal speed
limit
Voltage
polarity
Torque command
direction
+
-
1
0
+
CCW or positive direction
CCW or positive
direction
CCW or positive direction
CCW or positive
direction
-
CW or negative direction
CW or negative
direction
CW or negative direction
CW or negative
direction
0
1
+
CCW or positive direction
CW or negative
direction
CW or negative direction
CW or negative
direction
-
CW or negative direction
CCW or positive
direction
CCW or positive direction
CCW or positive
direction
0
+10/-10
Servo
motor
speed
[r/min]
Rated speed [r/min]
VLA applied voltage [V]
Forward rotation (CCW)
Forward rotation (CCW)
Reverse rotation (CW)
Reverse rotation (CW)