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Failsafe System Which Uses The Inverter - Mitsubishi Electric FR-A800 Instruction Manual

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Failsafe system which uses the inverter

3.7
Failsafe system which uses the inverter
When a fault is detected by the protective function, the protective function activates and outputs a fault signal. However, a
fault signal may not be output at an inverter's fault occurrence when the detection circuit or output circuit fails, etc. Although
Mitsubishi assures the best quality products, provide an interlock which uses inverter status output signals to prevent
accidents such as damage to the machine when the inverter fails for some reason. Also at the same time consider the system
configuration where a failsafe from outside the inverter, without using the inverter, is enabled even if the inverter fails.
Interlock method which uses the inverter status output signals
By combining the inverter output signals to provide an interlock as shown below, an inverter failure can be detected.
No.
Interlock method
Inverter protective function
a
operation
b
Inverter operating status
c
Inverter running status
d
Inverter running status
(a) Checking 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. (ALM signal is assigned to terminal A1B1C1
in the initial setting).
With this signal, check that the inverter operates
properly.
In addition, negative logic can be set. (ON when the
inverter is normal, OFF when the fault occurs.)
(b) 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.
(c) 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. (RUN signal is assigned
to terminal RUN in the initial setting.)
Check if RUN signal is being output while inputting a
start signal to the inverter. (STF signal is a forward
rotation signal, and STR is a reverse rotation signal.)
Even after the start signal is turned OFF, the RUN
signal is kept output until the inverter makes the motor
to decelerate and to stop. For the logic check,
configure a sequence considering the inverter's
deceleration time.
82
PRECAUTIONS FOR USE OF THE INVERTER
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.
Power
supply
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
(when output
at NC contact)
RES
Reset ON
ON
ON
STF
RH
Pr. 13 Starting
frequency
Reset
processing
ON
RY
RUN
Used signals
OFF
OFF
ON
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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