3.7 Failsafe system which uses the inverter When a fault is detected by the protective function, a fault signal is output. However, a fault signal may not be output at an products, provide an interlock which uses inverter status output signals to prevent accidents such as damage to the machine inverter's fault occurrence when the detection circuit or output circuit fails, etc. Although Mitsubishi assures the best quality 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. • When using various signals, refer to the following table and assign the functions by Pr.195 (Output terminal function selection) . • Changing the terminal assignment using Pr.195 Output terminal function selection may affect the other functions. Set parameters after confirming the function of each terminal. Checking by the output of the inverter fault signal ... (a) ALM signal is assigned to terminals A, B, and C in the initial setting). With this signal, check that the inverter operates properly.
When the inverter's protective function is activated and the inverter output is shut off, the Fault (ALM) signal is output. (The In addition, negative logic can be set. (ON when the inverter is normal, OFF when the fault occurs.) Output frequency Inverter fault occurrence (trip) ALM (when output at NC contact) RES Reset ON Checking the inverter operating status by 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. 62 3.
PRECAUTIONS FOR USE OF THE INVERTER 3.7 Failsafe system which uses the inverter No. Interlock method Check method Used signals Refer to page a Inverter protective function operation Operation check of an alarm contact. Circuit error detection by negative logic. Fault (ALM) signal 128 b Inverter operating status Operation ready signal check. Operation ready signal (RY) signal 127 c Inverter running status Logic check of the start signal and running signal. Start (STF or STR) signal Running signal (RUN) signal 127, 145 d Inverter running status Logic check of the start signal and output current.
Start (STF or STR) signal Output current detection (Y12) signal 129, 145 Output signal Pr.195 setting Positive logic Negative logic ALM 99 199 RY 11 111 RUN 0 100 Y12 12 112 NOTE ON Tim OFF ON OFF ON Reset processing (about 1 s)