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Failsafe system which uses the inverter
PRECAUTIONS FOR USE OF THE INVERTER
77
3
NOTE
• Changing the terminal assignment using Pr.190 and Pr.196 (output terminal function selection) may affect the other
functions. Set parameters after confirming the function of each terminal.
• For the details of the parameters and signals, refer to the FR-A800 Instruction Manual (Detailed).
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, if an inverter CPU fails in a system interlocked with the inverter's fault, start, and RUN signals,
no fault signal will be output and the RUN signal will be kept ON because the inverter CPU is down.
Provide a speed detector to detect the motor speed and current detector to detect the motor current and consider the backup
system such as performing a check as below according to the level of importance of the system.
(a) 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 current
is flowing through the motor while the motor coasts to stop, even after the inverter's start signal is turned OFF. For the
logic check, configure a sequence considering the inverter's deceleration time. In addition, it is recommended to check
the three-phase current when using the current detector.
(b) Command speed and actual operation check
Check for a gap between the actual speed and commanded speed by comparing the inverter's speed command and
the speed detected by the speed detector.
(d) 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 current flows into the motor.
Check if Y12 signal is being output while inputting a start signal to the inverter. (STF signal is a forward rotation signal,
and STR is a reverse rotation signal.) The Y12 signal is initially set to be output at 150% rated inverter current. Adjust
the level to around 20% using no load current of the motor as reference with Pr.150 Output current detection level.
Like the inverter running signal (RUN signal), even after the start signal is turned OFF, the Y12 signal is kept output until
the inverter stops the output to a decelerating motor. For the logic check, configure a sequence considering the
inverter's deceleration time.
• When using various signals, assign the functions to Pr.190 and
Pr.196 (output terminal function selection) referring to the
table on the left.
Output
signal
Pr.190 to Pr.196 setting
Positive logic Negative logic
ALM 99 199
RY 11 111
RUN 0 100
Y12 12 112
Inverter
Controller
System failure
To the alarm detection sensor
Sensor
(speed, temperature,
air volume, etc.)