Mitsubishi Electric 800 Series Instruction Manual (Function page 480

 Magnetic flux decay output shutoff and the Magnetic flux decay output
shutoff signal (X74 signal, Pr.850 = "2")
• Frequent starts/stops (inching) under Real sensorless vector control may cause an inverter failure or create a difference
in operation with the motor. The reason is that some magnetic flux is left in the motor at shutoff of the inverter output. If this
is the case, set Pr.850 = "2" (magnetic flux decay output shutoff) or turn ON the Magnetic flux decay output shutoff (X74)
signal to decay the magnetic flux at a stop, and then shut off the output.
• While Pr.850 = "2", deceleration starts at turning OFF of the start command, and the magnetic flux decay output shutoff is
activated when the estimated speed becomes lower than Pr.10 DC injection brake operation frequency.
• While the brake sequence function is active, the magnetic flux decay output shutoff is activated when the running frequency
drops to 0.5 Hz or Pr.13 Starting frequency, whichever is smaller.
• Inverter output voltage shutoff timing when Pr.850 = "2"
Normal operation
Start command
(STF, STR)
Speed command
(rotation per
second)
Pr. 10 DC injection
brake operation
frequency
Magnetic flux decaying
Output voltage
RUN ON
RY2
Mechanical brake
MC on the output side
*1 Maximum processing time of the magnetic flux decay
• Turning ON the Magnetic flux decay output shutoff (X74) signal starts the magnetic flux decay output shutoff regardless of
the Pr.850 setting. For the X74 signal, set "74" in any of Pr.178 to Pr.189 (Input terminal function selection) to assign
the function.
• Inverter output shutoff timing with X74 signal
X74 signal
X74
ON
Output voltage ON
RUN ON
Mechanical brake ON
MC on the output side
ON
*1 Maximum processing time of the magnetic flux decay
• Since the torque will decrease at the time of magnetic flux decay output shutoff, set up so the mechanical brake will
operate.
ON
Magnetic flux decay
processing time∗
ON
ON
ON
ON
Do not turn OFF MC
during this period
MRS signal
Magnetic flux decay
processing time∗
Output voltage
Mechanical brake
MC on the output side
Do not turn off MC
during this processing time
17.6 DC injection brake, zero speed control, servo lock, and magnetic flux decay output shutoff
During brake sequence
Start command
(STF, STR)
Speed command
(rotation per
minute)
Pr. 13 Starting
frequency or 0.5Hz
(whichever is lower)
Magnetic flux decaying
Output voltage
RUN
RY2
Mechanical brake
MC on the output side
MRS
ON
ON
RUN ON
ON
ON
ON
Magnetic flux
decay
processing time*
ON
ON
ON
ON
ON
Do not turn OFF MC
during this period
17. (G) Control Parameters
11
12
13
14
15
16
17
18
19
20
479