Mitsubishi Electric FR-A800, Instruction Manual

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Precautions for use of the inverter Failsafe system which uses the inverter
FR-A800 3 - 23
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 de-
tection circuit or output circuit fails, etc. Although Mitsubishi assures the best quality products, pro-
vide 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.
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.)
No. Interlock method Check method Used signals
Refer to
page
Inverter protective
function operation
Operation check of an alarm
contact.
Circuit error detection by
negative logic.
Fault output signal (ALM signal) 5-371
Inverter operating status Operation ready signal check. Operation ready signal (RY signal) 5-367
Inverter running status
Logic check of the start signal
and running signal. Start signal (STF signal, STR signal)
Running signal (RUN signal) 5-367,
5-430
Inverter running status
Logic check of the start signal
and output current.
Start signal (STF signal, STR signal)
Output current detection signal
(Y12 signal)
5-377,
5-430
Tab. 3-15: Different output signals of the frequency inverter can be used for interlocks
I001877E
Fig. 3-13: Contact B1-C1 opens when a fault occurs (initial setting)
Reset ON
Reset processing
(about 1s)
Output
fr
eque
nc
y
Time
ON
OFF
ON OFF
Inverter fault occurrence (trip)
ALM
(when output
at NC contact)
RES