If the internal safety circuit is operated normally, the terminal SO remains ON until E.SAF is displayed, and the terminal SO turns OFF when E.SAF is displayed.



SA is displayed when the terminals S1 and S2 are identified as OFF due to the internal safety circuit failure.



If another fault occurs at the same time as E.SAF, the other fault can be displayed.



If another warning occurs at the same time as SA, the other warning can be displayed.

For more details, refer to the Safety stop function instruction manual. (A PDF copy of this manual can be found in the enclosed CD-ROM. For how to use this CD-

ROM, refer to

page

31.)

FAILSAFE SYSTEM WHICH USES THE INVERTER

When a fault is detected by the protective function, the protective function activates and output a fault signal (ALM). However, a 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.

Interlock method

Inverter protective function

Operation check of an alarm contact.

operation

Circuit error detection by negative logic.

Inverter operating status

Operation ready signal check.

Logic check of the start signal and running

Inverter running status

signal.

Logic check of the start signal and output

Inverter running status

current.

 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.

• 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.

• 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.

Inverter

To the alarm detection sensor

Operation panel

Error definition

indication

E.OPT

Overspeed occurrence

E.OP1 to E.OP3

Speed deviation excess detection