8 Operation
8.7.4 Limiting Servomotor Speed during Torque Control
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8.7.4 Limiting Servomotor Speed during Torque Control
During torque control, the servomotor is controlled to output the specified torque, which means that the servomo-
tor speed is not controlled. Accordingly, when an excessive reference torque is set for the mechanical load
torque, it will prevail over the mechanical load torque and the servomotor speed will greatly increase.
This function serves to limit the servomotor speed during torque control to protect the machine.
(1) Speed Limit Mode Selection (Torque Limit Option)
(2) Internal Speed Limit Function
(3) External Speed Limit Function
The Principle of Speed Limiting
When the speed is outside of the allowable range, a torque that is proportional to the difference between the actual speed
and the speed limit is used as negative feedback to bring the speed back within the speed limit range. Accordingly, there is
a margin generated by the load conditions in the actual motor speed limit value.
With No Speed Limit
With Speed Limit
Parameter
Description
Pn002
n.
0
Uses the value set in Pn407 as the speed limit (internal speed limit function).
n.
1
Uses V-REF (CN1-5, 6) as an external speed limit input. Applies a speed limit using the input
voltage of V-REF and the setting in Pn300 (external speed limit function).
Pn407
Speed Limit During Torque Control
Setting Range
Setting Unit
Factory Setting
Setting Validation
0 to 10000
1 min
-1
10000
Immediately
Sets the servomotor speed limit value during torque control.
The setting in this parameter is enabled when Pn002 = n.
0
.
The servomotor’s maximum speed will be used when the setting in this parameter exceeds the maximum speed of the ser-
vomotor used.
Type
Signal
Name
Connector
Pin Number
Name
Input
V-REF
CN1-5
External Speed Limit Input
SG
CN1-6
Signal Ground
Inputs an analog voltage reference as the servomotor speed limit value during torque control.
The smaller value is enabled, the speed limit input from V-REF or the Pn407 (Speed Limit during Torque Control) when
Pn002 = n.
1
.
The setting in Pn300 determines the voltage level to be input as the limit value. Polarity has no effect.
Motor speed
Maximum speed
Danger of damage due to
excessive machine speed.
Motor speed
Speed limit
Safe operation with
speed limit.
Torque
Pn300
Speed Reference Input Gain
Setting Range
Setting Unit
Factory Setting
Setting Validation
150 to 3000
(1.50 to 30.0 V/rated speed)
0.01 V/rated speed
600
Immediately
Sets the voltage level for the speed that is to be externally limited during torque control.
With Pn300 = 600 (factory setting) and 6 V input from V-REF (CN1-5, 6), the actual motor speed is limited to the rated
speed of the servomotor used.
Speed
Position
Torque
INFO
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