Safety Circuit Design - Mitsubishi Electric Melsec-Q172DCPU User Manual

3 DESIGN

3.2.2 Safety circuit design

(1) Concept of safety circuits
When the Multiple CPU system is powered on and off, normal control output may
not be done momentarily due to a delay or a startup time difference between the
Multiple CPU system power supply and the external power supply (DC in
particular) for the control target.
Also, an abnormal operation may be performed if an external power supply fault
or Motion controller failure takes place.
To prevent any of these abnormal operations from leading to the abnormal
operation of the whole system and in a fail-safe viewpoint, areas which can result
in machine breakdown and accidents due to abnormal operations
(e.g. emergency stop, protective and interlock circuits) should be constructed
outside the Multiple CPU system.
(2) Emergency stop circuit
The circuit should be constructed outside of the Multiple CPU system or servo
amplifier. Shut off the power supply to the external servo amplifier by this circuit,
make the electromagnetic brakes of the servo motor operated.
(3) Forced stop circuit
(a) The forced stop of all servo amplifiers is possible in a lump by using the
forced stop input of Motion CPU modules. After forced stop, the forced stop
factor is removed and the forced stop canceled.
(The servo error detection signal does not turn on with the forced stop.)
The forced stop input cannot be invalidated in the parameter setting of
system setting.
Make the forced stop input cable within 30[m] (98.43[ft.]).
The wiring example for the forced stop input of Motion CPU module is
shown below.
Q61P QnUD
CPU
<Motion CPU module>
Forced stop
(Note-1): As for the connection, both "+" and "-" are possible.
Q17 D(S)
CPU
EMI.COM
EMI
Forced stop
24VDC
(Note-1)
24VDC
EMI.COM
EMI
(Note): The forced stop input can not be invalidated in the system settings.
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