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Function assignment of external terminal and control
4.15.5 Magnetic flux decay output shutoff signal (X74 signal)
...............Specifications differ according to the date assembled. Refer to page 484 to check the SERIAL number.
⋅ For the X74 signal, set "74" in any of Pr. 178 to Pr. 189 (input terminal function selection) to assign the function.
⋅ Operate a mechanical brake after turning X74 signal ON.
⋅ When the MC is provided on the inverter output side, turn X74 signal ON and open the MC after magnetic flux decay
operation time (refer to below) has elapsed.
* Maximum time of magnetic flux decay operation
Performing frequent start/stop (inching operation) during Real sensorless vector control may cause an inverter
fault (electronic thermal relay function fault: E.THT, etc) due to residual magnetic flux and an error in monitor
output (running speed, motor torque, load meter, torque command, torque current command, motor output).
In such a case, use magnetic flux decay output shutoff signal (X74) as output shutoff signal.
Turning X74 signal ON shuts off output after decaying motor residual magnetic flux.
Motor Capacity
(Pr. 80 setting)
2.2kW or lower 3.7kW to 11kW 15kW to 30kW 37kW to 55kW 75kW or higher
Magnetic flux decay
processing time
250ms 500ms 800ms 900ms 1100ms
REMARKS
⋅ When performing operation other than Real sensorless vector control, turning X74 signal ON immediately shuts off inverter
output.
⋅ During an automatic restart after instantaneous power failure or start-time online auto tuning under Real sensorless vector
control, turning X74 signal ON immediately shuts off inverter output.
⋅ When some other factor affecting output shutoff (inverter alarm, MRS signal ON, etc.) occurs during magnetic flux decay
operation, magnetic flux decay operation is stopped to immediately shut off output.
⋅ Pr.850 Brake operation selection is also available to enable the magnetic flux decay output shutoff.
CAUTION
⋅ Changing the terminal assignment using Pr. 178 to Pr. 189 (input terminal function selection) may affect the other functions. Set
parameters after confirming the function of each terminal.
⋅ Different from MRS signal, voltage is output during magnetic flux decay processing even if X74 signal turns ON. Take care not
to have an electrical shock.
⋅ If the timing of mechanical brake opening is early, motor shaft may be forced to turn by a gravity drop or external force. If the
timing of mechanical brake opening is late, overcurrent, stall prevention operation or electronic thermal relay function may be
activated. Use output frequency detection signal (FU) or output current detection signal (Y12) to perform the mechanical brake
opening suitable for the machine.
♦ Parameters referred to ♦
Pr. 850 Brake operation selection Refer to page 203
X74
Output voltage
RUN
Magnetic flux decay
processing time
*
Do not turn off MC
during this processing time
ON
ON
ON
ON
Mechanical brake
MC on the output side
Output voltage
RUN
Mechanical brake
MC on the output side
ON ON
Inverter output voltage shutoff timing
X74 signal
MRS
ON
ON
ON
ON
MRS signal