Mitsubishi Electric FR-D720-0.2K-G Instruction Manual page 59

Failsafe of the system which uses the drive unit
4) Checking the motor operating status by the start signal input to the drive unit and drive unit output current detection
signal.
The Output current detection (Y12) signal is output when the drive unit operates and currents flows in the motor. Check
if the Y12 signal is output when inputting the start signal to the drive unit (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 drive unit 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 Drive unit running (RUN) signal, the drive unit outputs for the period from the drive unit
decelerates until output to the motor is stopped, configure a sequence considering the drive unit deceleration time.
Output Pr. 190, Pr. 192 Setting
Signal Positive logic Negative logic
ALM 99
RY 11
RUN 0
Y12 12
NOTE
 Changing the terminal assignment using Pr. 190 and Pr. 192 (output terminal function selection) may affect the other
functions. Make setting after confirming the function of each terminal.
(2) Backup method outside the drive unit
Even if the interlock is provided by the drive unit status signal, enough failsafe is not ensured depending on the failure
status of the drive unit itself. For example, when the drive unit CPU fails, even if the interlock is provided using the drive
unit fault signal, start signal and RUN signal, there is a case where a fault signal is not output and RUN signal is kept
output even if a drive unit 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 drive unit by comparing the start signal to
the drive unit 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 drive unit starts decelerating even if the
start signal turns OFF. For the logic check, configure a sequence considering the drive unit 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 drive unit speed command
and detected speed of the speed detector.
System failure
48
 When using various signals, assign functions to Pr. 190 and
199
111
100
112
Controller
Drive unit
(speed, temperature,
To the alarm detection sensor
Pr. 192 (output terminal function selection) referring to the table
on the left.
Sensor
air volume, etc.)