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Failsafe of the system which uses the inverter
1
WIRING
(2) 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.
1) Start signal and actual operation check
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.
2) Command speed and actual operation check
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.
Inverter
Controller
System failure
To the alarm detection sensor
Sensor
(speed, temperature,
air volume, etc.)