Failsafe System Which Uses The Inverter - Mitsubishi Electric FR-A872-P Instruction Manual

3.6

Failsafe system which uses the inverter

When a fault is detected by the protective function, the protective function activates and outputs the Fault signal. However, the
Fault signal may not be output at an inverter's fault occurrence when the detection circuit or output circuit fails, etc. Although
Mitsubishi assures the best quality products, provide an interlock which uses inverter status output signals to prevent accidents
such as damage to the machine when the inverter fails for some reason. Also at the same time consider the system
configuration where a 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 output signals to provide an interlock as shown below, an inverter failure can be detected.
No. Interlock method
a Inverter protective function operation
b Inverter operating status
c Inverter running status
d Inverter running status
• When using various signals, assign the functions to Pr.190 to Pr.196 (Output terminal function selection) referring to
the table on the left.
Pr.190 to Pr.196 setting
Output
signal
Positive logic
ALM 99
RY 11
RUN 0
Y12 12
NOTE
• 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.
 Checking by using the Fault signal output from the inverter... (a)
When the inverter's protective function activates and the inverter output is stopped, the Fault (ALM) signal is output. (The ALM
signal is assigned to terminals A1, B1, and C1 in the initial setting). With this signal, check that the inverter operates properly.
In addition, negative logic can be set. (ON when the inverter is normal, OFF when the fault occurs.)
Inverter fault occurrence
(trip)
ALM
ON
(when output
at NC contact)
RES
Reset ON
 Checking the inverter operating status by using the Inverter operation ready signal output
from the inverter ... (b)
The Inverter operation ready (RY) signal is output when the inverter power is ON and the inverter becomes operative. Check
if the RY signal is output after powering ON the inverter.
Operation check of an alarm contact.
Circuit error detection by negative logic.
Operation ready signal check.
Logic check of the start signal and running
signal.
Logic check of the start signal and output
current.
Negative logic
199
111
100
112
Time
OFF
OFF
ON
Reset processing
(about 1 s)
Check method
3. PRECAUTIONS FOR USE OF THE INVERTER
3.6 Failsafe system which uses the inverter
Used signals
Fault (ALM) signal
Inverter operation ready (RY)
signal
Start (STF or STR) signal
Inverter running (RUN) signal
Start (STF or STR) signal
Output current detection (Y12)
signal
1
2
3
4
5
6
7
8
9
10
89