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Failsafe of the system which uses the
inverter
(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, when the inverter CPU fails, 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.
4) Checking the motor operating status by the start signal input to the inverter and inverter output current detection signal.
The output current detection signal (Y12 signal) is output when the inverter operates and currents flows in the motor.
Check if Y12 signal is output when inputting the start signal to the inverter (forward signal is STF signal and reverse
signal is STR signal). Note that the current level at which Y12 signal is output is set to 150% of the inverter rated current
in the initial setting, it is necessary to adjust the level to around 20% using no load current of the motor as reference with
Pr. 150 Output current detection level.
For logic check, as same as the inverter running signal (RUN signal), the inverter outputs for the period from the inverter
decelerates until output to the motor is stopped, configure a sequence considering the inverter deceleration time.
Output
Signal
Pr. 190 to Pr. 196 Setting
y When using various signals, assign functions to Pr.190 to Pr.
196 (output terminal function selection) referring to the table on
the left.
Positive logic Negative logic
ALM 99 199
RY 11 111
RUN 0 100
Y12 12 112
CAUTION
y Changing the terminal assignment using Pr. 190 to Pr. 196 (output terminal function selection) may affect the other functions. Set
parameters after confirming the function of each terminal.
Inverter
Controller
System failure
To the alarm detection sensor
Sensor
(speed, temperature,
air volume, etc.)