Mitsubishi Electric FR-A720-0.4K Instruction Manual page 207

(5) Brake operation selection under vector control (Pr. 802)
⋅ When pre-excitation is performed, select zero speed control or servo lock using Pr. 802.
Pr. 802 Setting Pre-excitation
0 (initial value) Zero speed control
1 Servo lock
⋅ The relationship between the DC injection brake operation and pre-excitation operation under each control
Control Method Control Mode
V/F control
Advanced magnetic flux
vector control
Real sensorless vector
control
Vector control
(6) Pre-excitation signal (LX signal)
⋅ When the LX signal is turned on under real sensorless vector control or vector control, pre-excitation (zero speed
control or servo lock) is exercised during a stop.
⋅ For the terminal used for LX signal input, set "23" in any of Pr. 178 to Pr. 186 to assign the function.
Zero speed control
Servo lock
CAUTION
⋅ Changing the terminal assignment using Pr. 178 to Pr. 189 (input terminal function selection) may affect the other functions. Make
setting after confirming the function of each terminal.
⋅ Performing pre-excitation (LX signal and X13 signal) under torque control (real sensorless vector control) may start the motor
running at a low speed even when the start command (STF or STR) is not input.The motor may run also at a low speed when
the speed limit value=0 with a start command input. Perform pre-excitation after making sure that there will be no problem in
safety if the motor runs.
⋅ Although FWD/REV of the operation panel is not lit during pre-excitation, note that voltage is applied to the motor.
⋅ Note that when offline auto tuning (Pr. 96 Auto tuning setting/status = "1 or 101") is performed during pre-excitation, offline auto
tuning is not executed but the motor starts.
Do not set Pr. 11 to "0, 8888" and Pr. 12 to "0" under orientation operation. Otherwise, the motor will not stop properly.
As stop holding torque is not produced, install a mechanical brake.
After the machine stops fully and the mechanical brake is applied, switch the LX signal (pre-excitation) off.
♦ Parameters referred to ♦
Pr. 13 Starting frequency Refer to page 170
Pr. 71 Applied motor Refer to page 180
Pr. 178 to Pr. 189 (Input terminal function selection)
Pr. 422 Position loop gain Refer to page 137
Even under load, an attempt is made to maintain 0r/min to keep the motor shaft stopped. Note that
if the shaft is overcome and turned by external force, it does not return to the original position.
Position control is not exercised and only speed control is carried out to perform operation.
Even under load, an attempt is made to maintain the motor shaft position. Note that if the shaft is
turned by external force, it returns to the original position after the external force has gone away.
Since position control is exercised, you can adjust this position loop gain using Pr. 422 Position loop gain.
Pr. 802 Pr. 850
⎯ ⎯
⎯ ⎯
⎯
Speed
⎯
⎯
Torque
⎯
0
Speed
1
⎯
Torque
⎯
Position
When Pr. 850 = 1
(Hz)
Normal operation Pr. 11
Operation time
LX signal
CAUTION
Refer to page 222
Motor brake and stop operation
Description
Decelerates to Stop
⎯
DC Injection brake
⎯
DC Injection brake
0 DC Injection brake
1 Zero speed
0 DC Injection brake
1 Zero speed
⎯
Zero speed
⎯
Servo lock
⎯
Zero speed
⎯ ⎯
Pr. 10
Operation
frequency
Normal operation
ON
X13-ON
LX-ON
(Pr. 11 = "8888")
⎯
DC Injection brake
⎯
DC Injection brake
Zero speed Zero speed
Zero speed Zero speed
Zero speed Zero speed
Servo lock Servo lock
Zero speed Zero speed
⎯
Servo lock
Time
197
4