Figure 6-7 shows a simple grounded system. Even
though the grounds are shown at different points, the
potentials at these points are essentially the same since
they are connected to a common conductor.
I D E N T I F I C AT I O N C O D I N G
AT S TA RT O F C I R C U I T
Any wire that completes the circuit to the ground
network for the equipment is designated with the letter
N. Any wire so designated may come in contact with
ground at any point without causing malfunctions to the
TB17
equipment.
A grounded circuit has advantages since it reduces
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overall weight by using fewer conductors. This results
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in a reduction in cost and space requirements. Other
advantages are that troubleshooting is simplified to
REF
some extent and the impedance of the ground return
path is lower than that of a wire conductor. The
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grounded system also has disadvantages. Short circuits
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result when a bare spot on any ungrounded conductor
touches ground.
A
P107
J107
A
UNGROUNDED SYSTEMS
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THROUGH CONNECTOR
The term ungrounded system means that the circuit
is in no way connected to ground. All conductors are
run from the power source to the loads. Circuits of this
type are often referred to as being above ground. The
ungrounded system has a number of advantages. It
prevents one circuit from feeding into another. No
malfunction of equipment occurs should one conductor
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THROUGH SWITCHING DEVICE
become accidentally grounded. The circuits are
completely insulated from each other. The system has
the disadvantage of adding more weight because it
requires more conductors than the grounded system.
G
G
This results in added cost and space requirements.
ELECTRICAL SAFETY PRECAUTIONS
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THROUGH LOAD
We do not normally do repair work on energized
circuits. But, when repairs on operating equipment
must be made, the work should be done only by
ASfO0006
experienced personnel under the supervision of the
Figure 6-6.--Example of wire identification code use.
senior petty officer of the work center, if possible.
Every known safety precaution should be carefully
GROUNDED SYSTEMS
A
Almost all of the electrical and electronic circuits
you work with are grounded. This means that one leg of
the circuit is connected to a common conductor, such as
G
a structural member (frame) of the equipment. When
the grounded leg of the circuit is connected to a good
electrical conductor, this conductor may serve as one
ASf06007
leg of the circuit. No separate conductor is needed for
this leg of the circuit.
Figure 6-7.--Grounded system.
6-7
