CEAG Notlichtsysteme GmbH
66
Failures
Assembly and Operating Instructions
Automatic Test System AT-S
+
with STAR
+
Technology
9.1.2 Screen connection
The type of screen connection depends mainly on the anticipated interference. Grounding the screen at one end
(1) is necessary to suppress electrical fields. Interference caused by a magnetic alternating field on the other hand
can only be suppressed when the screen is connected at both ends (2).
Ground loops with their familiar disadvantages must be avoided when connecting a screen at both ends. High
voltage can be induced in large loops and this in turn causes failures. The right way to avoid ground loops is to
make a starshaped ground or to take a Y3-condenser.
9.1.3 The fail-safe system
Companies therefore protect their plants from induced EMI by screening their cables. Now the cable screen only
has to be connected inside the control cabinet to make the connection to ground. This connection should be low-
impedance and with a low inductive resistance. Socalled screen quick connectors (SSA 5-10) should be used for
this.
The screen quick connector SSA 5-10 gets grounded by potential connecting lines.
It is of course rare for just one cable to be routed into a control cabinet. In most cases a number of data transfer,
supply and circuit cables have to be laid into the cabinet. However every opening in the cabinet that can be avoided
is an avoidable cause of interference.
Note:
The avoidance of ground loops contributes to the trouble-free
operation of a system.
Condenser 220nF Y3
4 KV
Summary of Contents for Ceag AT-S+ C0
Page 76: ...400 71 860 177 XXX 07 12 WK...
