Delta EB3000 Series User Manual page 456

A-3-2 Ground Loops
A ground loop occurs when the pieces of equipment are connected to more than one grounding path.
In this case, the ground current may return to the grounding electrode via more than one path. There
are three methods to prevent ground loops:
1. Use a common power circuit
2. Single point grounding
3. Isolate signals, e.g. by photocouplers
Equipment
A
In order to avoid "Common Mode Noise", use parallel wires or twisted pair wiring. Follow this rule and
also avoid long wires, it is suggested to place the two wires as close to each other as possible.
A-3-3 Earthing Systems
The international standard IEC60364 distinguishes three different earthing system categories, using
the two-letter codes TN, TT, IT.
The first letter indicates the type of earthing for the power supply equipment (generator or
•
transformer).
T: One or more points of the power supply equipment are connected directly to the same earthing
point.
I: Either no point is connected to earth (isolated) or it is connected to earth via high impedance.
The second letter indicates the connection between earth and the power supply equipment.
•
T: Connected directly to earth (This earthing point is separate from other earthing points in the
power supply system.)
N: Connected to earth via the conductor that is provided by the power supply system
The third and fourth letter indicate the location of the earth conductor.
•
S: Neutral and earth conductors are separate
C: Neutral and earth are combined into a single conductor
Cable
Equipment
B
Earth plane
Figure A-7
Appendix A. EMC Standard Installation GuideEB3000
Accompanying cable
Equipment
A
Very good
Earth plane
Figure A-8
A-9
Good
Cable
Equipment
B
Cable