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Failsafe of the system which uses the inverter
3.6
Failsafe of the system which uses the inverter
When a fault occurs, the inverter trips to output a fault signal. However, a fault output signal may not be output at an inverter
fault occurrence when the detection circuit or output circuit fails, etc. Although Mitsubishi assures best quality products,
provide an interlock which uses inverter status output signals to prevent accidents such as damage to machine when the
inverter fails for some reason and at the same time consider the system configuration where failsafe from outside the inverter,
without using the inverter, is enabled even if the inverter fails.
(1) Interlock method which uses the inverter status output signals
By providing interlocks, inverter fault can be detected. For the interlocks, use different status output signals of the
inverter (virtual terminals of the CC-Link communication) in combinations shown below.
No.
Interlock Method
Inverter protective
1)
function operation
2)
Inverter running status
3)
Inverter running status
4)
Inverter running status
1) Check by the output of the inverter fault signal
When the inverter's protective function activates and the
inverter trips, the fault output signal (ALM signal) is
output.
With this signal, you can check if the inverter is operating
properly.
In addition, negative logic can be set (ON when the
inverter is normal, OFF when a fault occurs).
2) Checking the inverter operating status by the inverter
operation ready completion signal
Operation ready signal (RY signal) is output when the
inverter power is on and the inverter becomes operative.
Check if the RY signal is output after powering ON the
inverter.
3) Checking the inverter operating status by the start signal
input to the inverter and inverter running signal.
The inverter running signal (RUN signal) is output when
the inverter is running.
Check if RUN signal is output when inputting the start
signal to the inverter (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 inverter
decelerates until output to the motor is stopped,
configure
a
sequence
deceleration time
REMARKS
RUN signal is assigned to the terminal Y0 in the initial status. In the initial setting, the operating status of the inverter can
be checked with the lamp, etc., which is connected to the terminal Y0, or a virtual terminal of CC-Link communication.
44
Check Method
Operation check of an alarm contact
Circuit error detection by negative logic
Operation ready signal check
Logic check of the start signal and
running signal
Logic check of the start signal and
output current
considering
the
inverter
Used Signals
Fault output signal
(ALM signal)
Operation ready signal
(RY signal)
Start signal
(STF signal, STR signal)
Running signal (RUN signal)
Start signal
(STF signal, STR signal)
Output current detection signal
(Y12 signal)
Inverter fault occurrence
(trip)
ALM
ON
Inverter reset
Reset ON
Power
ON
supply
ON
STF
RH
Pr. 13 Starting frequency
Reset
processing
ON
RY
RUN
Refer to Page
61, 170
61, 169
60, 61, 169
60, 61, 172
OFF
ON
OFF
Reset processing
(about 1s)
OFF
OFF
ON
DC injection brake
operation point
DC injection
brake operation
Time
OFF
ON
OFF
Time
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