February 2012 6 – 73
Sources of
interference
Also observe possible sources of interference that may have a negative effect on the control and
its peripherals.
Interference is mainly produced by capacitive and inductive coupling from electrical conductors or
from device inputs/outputs, such as ...
Strong magnetic fields, e.g. from transformers, electric motors, magnetic clamping tables
Relays, contactors and solenoid valves
High-frequency equipment, pulse devices, and stray magnetic fields from switch-mode power
supplies
Adjoining welding facilities
Power lines and leads to the above equipment
Open lines on serial data interfaces (e.g. RS-232)
Make sure that …
There is a minimum distance of 20 cm from the control and its leads to interfering equipment.
There is a minimum distance of 10 cm from the control and its leads to cables that carry
interference signals. For cables in metallic ducting, adequate decoupling can be achieved by
using a grounded separation shield.
The cross section of potential compensating lines is at least 6 mm
2
.
Genuine HEIDENHAIN cables, connectors and couplings are used.
Cover plates are available for the ribbon cables.
Contamination Pay special attention to contaminated units (oil, grease, dust, etc.)!
What could be the reason for the contamination?
Some examples:
Machining of cast blanks or graphite
Coolant or coolant vapor
Defective filter system in the electrical cabinet (filter pads)
Oil or oil vapor
Oil in the compressed-air system
Door of electrical cabinet open
Contact the machine manufacturer if these conditions are not fulfilled!
The deposition of dust from the ambient air, precipitation of chemical contamination contained in
the air or the natural formation of dew after switching off the machine can form a conductive layer
on the live parts of electrical equipment and may cause flashovers resulting in corresponding
damage.
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