Safety Circuit Design - Mitsubishi Electric A173UHCPU User Manual

2. DESIGN
100/200VAC

2.3.2 Safety Circuit Design

(4) Grounding
The motion system may malfunction as it is affected by various noises such as
electric path noises from the power supply lines, radiated and induced noises
from other equipment, servo amplifiers and their cables, and electromagnetic
noises from conductors. To avoid such troubles, connect the earthing ground of
each equipment and the shield grounds of the shielded cables to the earth.
Also use ferrite cores to prevent the sneak noises of the SSCNET from
entering.
For grounding, use the exclusive ground terminal wire of each equipment or a
single-point earth method to avoid grounding by common wiring, where
possible, since noises may sneak from other equipment due to common
impedances.
Line noise filter
(1) Concept of safety circuits
When the motion controller is powered on-off, proper outputs may not be
provided temporarily due to the delays and rise times of the motion controller
power supply and external I/O control power supplies (especially DC).
For example, if the motion controller is powered on after external process
power is switched on in the DC output module, the DC output module may
provide a false output instantaneously at power-on of the motion controller.
Therefore, the circuit must be made up to enable the motion controller to be
powered on first. Also, abnormal operations may be performed when the
external power supply becomes faulty or the motion controller fails.
To prevent these abnormal operations from leading to the abnormal operation
of the whole system and also from the fail-safe viewpoint, configure up a circuit
outside the motion controller for the areas which may lead to machine damage
and accidents due to abnormal operations (e.g. emergency stop, protective
and interlock circuits).
Motion controller
Ferrite cores
SSCNET
Servo amplifier
2 − 12
Panel computer
SM