EMC Information Installation
BUG 3/2/20 Basic Feed Unit 21
Baumüller Nürnberg GmbH 5.96064.02
• Avoid reserve loops on overlong cables.
• You must ground reserve lines at both ends (this has an additional screening effect, avoids ca-
pacitively coupled, dangerous touch voltages).
Grounding
• From an EMC point of view, classical star grounding is no longer adequate for reducing the influ-
ence of disturbances at relatively high frequencies that occur as a result of converter operation.
Better results can be achieved by a reference surface that must be linked to the devices' frame
grounds over a wide area (e.g. a bare, metallic mounting plate and parts of the housing).
If it is not possible to use a broad reference place, it is sensible to mount the main equipotential
busbar directly next to the converter, since this device generates the greatest potential jumps,
compared with the other components in the switching cabinet, due to the steep switching edges
(the ground connection should be less than 30 cm long if possible).
• Route all earth conductors and screens as closely as possible above the frame ground to prevent earth
circuits.
• If it is possible to earth the controller reference voltage, make this connection with cabling that has
as large a cross-section as possible and is less than 30 cm long.
• Remove insulating layers, such as varnish, adhesives, etc., from the frame ground connections. If nec-
essary, use DIN 6798 serrated lock washers or similar to ensure a permanent, conductive contact. To
prevent corrosion of frame ground connections, use suitable pairs of metals (electrochemical displace-
ment series), and keep conductive electrolytes away from the connection by means of a protective
coating (e.g. grease).
• Always connect screens at both ends to the frame ground; the connection should be over a wide
area and conductive. This is the only way to suppress the effects of magnetic or high-frequency
noise interference fields. If there are problems with earth circuits (e.g. double earth fault of the
specified value conductor screen), the receive side should be galvanically connected and the
transmit side capacitively connected.
• When routing cable screens through panels that separate different EMC areas, the cables must be
in contact with the panel.
Cables that are routed through the outer panels of screening housings without special measures
(e.g. filtering), can have an adverse effect on the screening capability of the housing. For this rea-
son, you must make a conductive connection of the cable screens to the screening outer panel at
the point at which the cable enters the housing.
The distance of the last screen contact point to the exit from the cabinet must be as short as possible.
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