45
Failsafe of the system which uses the drive unit
3
PRECAUTIONS FOR USE OF THE DRIVE UNIT
3.5 Failsafe of the system which uses the drive unit
When a fault occurs, the drive unit trips to output a fault signal. However, a fault output signal may not be output at a drive unit
fault occurrence when the detection circuit or output circuit fails, etc. Although Mitsubishi assures best quality products,
provide an interlock which uses drive unit status output signals to prevent accidents such as damage to machine when the
drive unit fails for some reason and at the same time consider the system configuration where failsafe from outside the drive
unit, without using the drive unit, is enabled even if the drive unit fails.
(1) Interlock method which uses the drive unit status output signals
By combining the drive unit status output signals to provide an interlock as shown below, a drive unit failure can be
detected.
No. Interlock Method Check Method Used Signals Refer to Page
1)
Drive unit protective
function operation
Operation check of an alarm contact
Circuit error detection by negative logic
Fault output signal
(ALM signal)
109
2) Drive unit operating status Operation ready signal check
Operation ready signal
(RY signal)
108
3) Drive unit running status
Logic check of the start signal and
running signal
Start signal
(STF signal, STR signal)
Running signal (RUN signal)
104, 108
4) Drive unit running status
Logic check of the start signal and output
current
Start signal
(STF signal, STR signal)
Output current detection signal
(Y12 signal)
104, 111
1)Check by the drive unit fault output signal
When the drive unit's protective function activates and the
drive unit trips, the fault output signal (ALM signal) is
output. (ALM signal is assigned to terminal ABC in the
initial setting).
With this signal, you can check if the drive unit is operating
properly.
In addition, negative logic can be set (ON when the drive
unit is normal, OFF when the fault occurs).
2)Checking the drive unit operating status by the drive unit
operation ready completion signal
Operation ready signal (RY signal) is output when the
drive unit power is ON and the drive unit becomes
operative.
Check if the RY signal is output after powering ON the
drive unit.
3) Checking the drive unit operating status by the start signal
input to the drive unit and drive unit running signal.
The drive unit running signal (RUN signal) is output when
the drive unit is running (RUN signal is assigned to
terminal RUN in the initial setting).
Check if RUN signal is output when inputting the start
signal to the drive unit (forward signal is STF signal and
reverse signal is STR signal). For logic check, note that
RUN signal is output for the period from the drive unit
decelerates until output to the motor is stopped, configure
a sequence considering the drive unit deceleration time.
ON
Reset processing
(about 1s)
OFF
Reset ON
Rotation
speed
ALM
(when output
at NC contact)
RES
Drive unit fault occurrence
(trip)
Time
OFF
ON
Time
Power
supply
Rotation speed
STF
RH
RY
Reset
processing
ON OFF
ON OFF
ON OFF
ON
DC injection brake
operation point
DC injection
brake operation
RUN
ON OFF
