Failsafe Of The System Which Uses The Inverter - Mitsubishi Electric FR-D720S SC EC Instruction Manual

Precautions for use of the inverter
4.1.1

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 sta-
tus output signals to prevent accidents such as damage to machine when the inverter fails for
some reason.
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.
Interlock method which uses the inverter status output signals
By combining the inverter status output signals to provide an interlock as shown below, an in-
verter alarm can be detected.
Interlock Method
Inverter protective
function operation
Inverter running
status
Tab. 4-1: Different output signals of the frequency inverter can be used for interlocks
Check by the output of the inverter fault signal
When the fault occurs and trips the inverter, the fault output signal (ALM signal) is output (ALM
signal is assigned to terminal ABC in the initial setting). Check that the inverter functions prop-
erly. In addition, negative logic can be set (on when the inverter is normal, off when the fault oc-
curs).
Fault output signal (ALM)
(when output at NC contact)
Fig. 4-2: Contact B-C opens when a fault occurs (initial setting)
4 - 4
Check Method
Operation check of an alarm contact
Circuit error detection by negative logic
Operation ready check signal
Logic check of the start signal and running
signal
Logic check of the start signal and output
current
Inverter fault occurrence
(trip)
Reset (RES)
Reset ON
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)
OFF ON (no Alarm)
ON
OFF
Reset processing
(about 1s)
Operation
Refer to
Page
6-102
6-101
6-86
6-101
6-86
6-105
Time
I001877E