4 Operation
4.8.8 Speed Limit Detection Signal (/VLT)
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4.8.8 Speed Limit Detection Signal (/VLT)
This function limits the speed of the servomotor to protect the machine.
A servomotor in torque control is controlled to output the specified torque, but the motor speed is not con-
trolled. Therefore, if an excessive reference torque is set for the load torque on the machinery side, the speed
of the servomotor may increase greatly. If that may occur, use this function to limit the speed.
Note: The actual limit value of motor speed depends on the load conditions of the servomotor.
The parameters related to the speed limit, such as for selecting the speed limit method, are described next.
(1) Signals Output during Servomotor Speed Limit
The following signal is output when the motor speed reaches the limit speed.
Note: Use parameter Pn50F.1 to allocate the /VLT signal for use. For details, refer to 3.3.2 Output Signal Allocations.
(2) Speed Limit Setting
Select the speed limit mode with Pn002.1.
With No Speed Limit With Speed Limit
Motor speed
Time
Maximum speed
Danger of damage due to
critical speed.
Motor speed
Limiting speed
Safe operation with
speed limit.
Time
Type
Signal
Name
Connector
Pin Number
Setting Meaning
Output /VLT Must be allocated
ON (closed) Servomotor speed limit being applied.
OFF (open) Servomotor speed limit not being applied.
Parameter Meaning
When
Enabled
Classification
Pn002
n.
0
[Factory setting]
VLIM (the speed limit value during torque control) is
not available. Uses the value set in Pn407 as the speed
limit (internal speed limit function).
After restart Setup
n.
1
VLIM operates as the speed limit value (external speed
limit function).
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