Mitsubishi Electric FR-D720S-008SC, Оригинальная инструкция

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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 Electric 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.
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 inverter alarm can be detected.
Backup Method Outside the Inverter
Even if the interlock is provided by the inverter status signal, enough failsafe is not ensured depending on the failure status of the
inverter itself. For example, even if the interlock is provided using the inverter fault output signal, start signal and RUN signal
output, there is a case where a fault output signal is not output and RUN signal is kept output even if an inverter fault occurs.
Provide a speed detector to detect the motor speed and current detector to detect the motor current and consider the backup
system such as checking up as below according to the level of importance of the system. Check the motor running and motor
current while the start signal is input to the inverter by comparing the start signal to the inverter and detected speed of the speed
detector or detected current of the current detector. Note that the motor current runs as the motor is running for the period until
the motor stops since the inverter starts decelerating even if the start signal turns off. For the logic check, configure a sequence
considering the inverter deceleration time. In addition, it is recommended to check the three-phase current when using the
current detector.
Check if there is no gap between the actual speed and commanded speed by comparing the inverter speed command and detected
speed of the speed detector.
Interlock Method Check Method Used Signals Refer to
Inverter protective function
operation Operation check of an alarm contact
Circuit error detection by negative logic Fault output signal
(ALM signal)
Refer to chapter
"
Parameter
"
of the Instruction Manual
Inverter runnning status
Operation ready signal check
Operation ready signal
(RY signal)
Logic check of the start signal and
running signal
Start signal
(STF signal, STR signal)
Running signal (RUN signal)
Logic check of the start signal and
output current
Start signal
(STF signal, STR signal)
Output current detection signal
(Y12 signal)
System failure
Controller
Inverter
Sensor
(speed, temperature,
air volume, etc.)
To the alarm detection sensor