Reo Elektronik REOTRON MDW 700, Руководство по эксплуатации

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REOTRON MDW 700
Operating instructions
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14.0 Interference prevention
14.1 Earthing
Correct earthing of electronic controls is highly important for two reasons:
First it ensures the safety of operators and service personnel, and secondly it provides a fail-safe opera-
tion of the equipment. Therefore, in addition to providing protective earthing, in accordance to DIN stand-
ards, it also provides an earth path for pulse interference produced during operation. For the latter, con-
trollers that are mounted onto a chassis–plate in a control panel should be bonded to earth with the
shortest possible connection and the largest possible earth contact area and also, for example, onto the
centrally bonded chassis-plate. The reason for this is to ground high-frequency interferences produced by
switching on the mains (contactors, relays, switches) before they cause fault conditions. If the earth con-
ductors are too long and if they run together with other cables, in one cable duct, then they are unsuitable
for grounding high-frequency noise.
The more complex the unit and the more "intelligent" the functions - especially serial bus connections –
then the more important it is to use correct earthing techniques.
14.2 Control cables
Control cables also are "antennas" that receive interference produced by other loads. Signal cables that
are run alongside power cables can generate voltage spikes through inductive and capacitive cross-
coupling. Therefore control conductors should not be mixed with power cables in the same cable ducting.
If this cannot be avoided then shielded cables should be used. In particular cables from inverters to mo-
tors are very critical because of the presence of high-speed switching. There should be maximum dis-
tance between control cables output cables from frequency inverters. The shielding around the control
conductors should be grounded onto a large contact area (earthed mounting plate) at the equipment end.
14.3 Interference protection of other external components and equipment
Contactors produce extreme Burst-interferences on switching. Contactor coils must be connected with
RC-snubbers.
Suitable RC-snubbers can be obtained from switch manufacturers.
Magnets / magnetic valves are also interference sources in the same way as contactors. RC- snubbers
and varistors can be components and varistors can be connected across these components
Frequency inverters are to connect to a mains filter recommended by the manufacturer.
Motor wires should be shielded and routed away from control cables.