5.3 Description of Function Codes 5.3.8 J codes (Applied functions)
Overload stop function (Torque limiting P (Gain), Torque limiting I (Integral time),
Current limiting level)
Refer to the J68 item.
Servo lock (Gain, Completion timer, Completion range)
Servo lock (Gain switching time, Gain 2)
Servo lock
This function holds the motor within the positioning completion range specified by J99 for the period specified by
J98 even if an external force applies to the motor. The servo lock function is available only at vector control with
speed sensor (F42=6, 16). By assigning servo lock command “LOCK” to the digital input terminal and turning it ON,
the servo lock function is enabled.
The servo lock operates at low speed, and if used with an external force applied for a long period of time,
there is a risk of overheat protection being triggered. Inverter output will be at low frequency when the
servo lock is applied, and therefore the servo lock should be used in the current rating 150%/3 s,
80%/continuous range to act as inverter thermal limiting. (The carrier frequency is automatically limited
to the upper limit of 5 kHz.)
Startup conditions of servo lock
Servo lock control starts when the following conditions are met:
F38 = 0
(Use actual speed as a decision criteria)
F38 = 1
(Use reference speed as a decision criteria)
Run command OFF, or Reference frequency < Stop frequency (F25)
“LOCK” (“Servo lock command”) ON (Assignment of “LOCK” (E01 to E05 data = 47))
The actual speed is less than the stop
frequency (F25).
The reference speed is less than the stop
frequency (F25).
Operation examples
Fig. 5.3-38 Typical control sequence of servo lock
When the servo lock command is ON, the inverter keeps on outputting voltage on output terminals [U], [V] and
[W] even if a run command is OFF and the motor seems to be in stop state.
Failure to observe this could result in electric shock.
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