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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 FL remote communication) in combinations shown below.
No. Interlock Method Check Method Used Signals Refer to Page
1)
Inverter protective
function operation
Operation check of an alarm contact
Circuit error detection by negative logic
Fault output signal
(ALM signal)
59
2) Inverter running status Check of the reset release signal
Reset release signal
(READY signal)
59
3) Inverter running status
Logic check of the start signal and
running signal
Start signal
(STF signal, STR signal)
Running signal (RUN signal)
57, 59
4) Inverter running status
Logic check of the start signal and
output current
Start signal
(STF signal, STR signal)
Output current detection signal
(Y12 signal)
57, 59
1)Checking by the inverter fault output 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.
2)Checking the inverter operation status by the reset cancel
signal
Reset cancel signal (READY signal) is output when the
reset operation of the inverter is cancelled by turning ON
the power of the inverter.
Check if the READY signal is output after the reset
operation of the inverter is canceled.
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 considering the inverter deceleration time.
ON
Reset processing
(about 1s)
OFF
Reset ON
Output frequency
ALM
Error reset
Inverter fault occurrence
(trip)
Tim
e
OFF
ON
Time
Power
supply
Output frequency
STF
RH
READY
Reset
processing
Pr. 13 Starting frequency
ON OFF
ON OFF
ON OFF
ON
DC injection brake
operation point
DC injection
brake operation
RUN
ON OFF