Mitsubishi Electric FR-A820-00046 Instruction Manual page 848

(G) Control parameters
● Inverter output shutoff timing with X74 signal
Mechanical brake
MC on the output side
* Maximum time for the magnetic flux decay operation
Fig. 5-331:
● Since the torque will decrease at the time of magnetic flux decay output shutoff, set up so the
mechanical brake will operate.
● Magnetic flux decay output shutoff will be canceled at the time of restart and when the Pre-
excitation/servo ON(LX) signal/External DC injection brake operation start (X13) signal is turned ON.
● When the MC is installed on the inverter output side, set up so the MC is released after the
magnetic flux decay operation time (see below) has passed.
Motor capacity
(Pr. 80 setting value)
Magnetic flux decay process time
Tab. 5-305: Magnetic flux decay operation time
NOTES When operating in anything other than the Real sensorless vector control, the inverter will imme-
diately shutoff the output when the X74 signal is turned ON.
Even at the time of Real sensorless vector control, the inverter will immediately shutoff the output
when the X74 signal is turned ON during the automatic restart after instantaneous power failure
and online auto tuning during the start up.
When other output shutoff trigger (inverter fault, turning ON the MRS signal, etc.) occurs during
the magnetic flux decay operation, the magnetic flux operation is terminated, and the output is
shut off immediately.
Unlike the MRS signal, voltage is output during the magnetic flux decay output shutoff operation,
so take caution on electric shocks.
When the release timing of the mechanical brake is too fast, the motor shaft may be rotated by
dropping or external force. When the release timing is too late, the overcurrent prevention opera-
tion or electronic thermal O/L relay may operate, so perform release of the mechanical brake
matching the equipment utilizing the output frequency detection (FU) signal and output current
detection (Y12) signal.
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.
5 - 668
X74 signal
ON
X74
Output voltage
ON
ON
RUN
ON
ON
Inverter output shutoff timing with X74 signal
2.2 kW or
Magnetic flux decay
processing time*
Output voltage
Mechanical brake
MC on the output side
Do not turn off MC
during this processing time
3.7 kW to
lower 11 kW
250 ms 500 ms
MRS signal
MRS ON
ON
RUN ON
ON
15 kW to 30 kW 37 kW to 55 kW
800 ms 900 ms
Parameters
ON
I002754E
75 kW or
higher
1100 ms