195NA493.10
1
2
90°
1
Fieldbus cable
2
Minimum 200 mm distance
Illustration 3.4 Cable Routing
3.2 Bus Cabling
3.2.1 EMC Precautions
The following EMC precautions are recommended to
achieve interference-free operation of the BACnet network.
More EMC information is available in the
VLT
®
DriveMotor
FCP 106 and FCM 106 Design Guide
.
NOTICE
Ensure compliance with relevant national and local
regulations, for example in PE connection.
3.2.2 Screen
For installing the bus cable on MS/TP, 2 different strategies
can be followed, each with advantages and disadvantages:
•
single ground of screen
•
multiple ground of screen
3.2.3 Single Ground Screen
The single ground screen is specified in the ANSI/ASRAHE
135-2004 standard. The solution benefits by having only
one ground connection of the screen, by doing so the risk
of ground loop of equalising current is heavily reduced. In
these systems the screen of the MS/TP cables must be
isolated from ground at all stations, except one. At each
station, the screens from the 2 cables must be connected
with each other, and isolated from ground. The best
solution for this connection is to use shrink tubes. The
single ground sscreen is a good approach where the
system uses long bus cables. For connection of 2 buildings
over the same MS/TP bus cable, consider the use of fibre
optic cable. Fibre optic cable prevents a lightning stroke
transferring from one building to another, and the
problem with difference in ground potential can be
ignored.
3.2.4 Multiple Ground Screens
When the distance between the individual frequency
converter is limited (for example, inside a cabinet or in one
control room), Danfoss recommends connecting the screen
to ground at both ends of the bus cable. This ensures the
maximum protection from EMC noise. Connecting the
screen at each end requires that each BACnet device has
the same ground potential or an equalizing current flow in
the screen of the cable. It causes disturbance and poor
performance of the system. Low impedance to ground
connection of the screen can be achieved by connecting
the surface of the screen to ground, with a cable clamp or
a conductive cable gland. The various clamps and brackets
supplied enable a proper ground connection of the
BACnet cable screen.
Danfoss recommends connection of the screen to ground
at both ends of the bus cable, to ensure maximum
protection from EMC noise. Connecting the screen at each
end requires that each BACnet device has the same
ground potential, otherwise an equalising current flows in
the screen of the cable. This current causes disturbance
and poor performance of the system. Alternatively, the
screen can be isolated from the housing of the frequency
converter using shrink-tubing. Routing of the BACnet cable
must be established with correct distance to other cables,
such as mains or motor cable
Installation
VLT
®
DriveMotor FCP 106 & FCM 106 BACnet Operating Instructions
MG03O102 - Danfoss A/S
©
12/2013. All rights reserved.
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Summary of Contents for VLT DriveMotor FCP 106
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