KEPCO ABC-DM SERIES - Manual (Page 29)

ABC 040104
2-5
2.7.2 SOURCE POWER CONNECTIONS
Source power is connected to the power supply via the three-wire power input cable supplied.
See Table 1-3 for source power specifications.
2.7.3 D-C OUTPUT GROUNDING
Connections between the power supply and the load and sensing connections may, despite all
precautions such as shielding, twisting of wire pairs, etc., be influenced by radiated noise, or
“noise pick-up”. To minimize the effects of this radiated noise the user should consider ground-
ing one side of the power supply/load circuit. The success of d-c grounding requires careful
analysis of each specific application, however, this recommendation can only serve as a gen-
eral guideline.
One of the most important considerations in establishing a successful grounding scheme is to
avoid GROUND LOOPS. Ground loops are created when two or more points are grounded at
different physical locations along the output circuit. Due to the interconnection impedance
between the separated grounding points, a difference voltage and resultant current flow is
superimposed on the load. The effect of this ground loop can be anything from an undesirable
increase in output noise to disruption of power supply and/or load operation. The only way to
avoid ground loops is to ensure that the entire output/load circuit is fully isolated from ground,
and only then establish a single point along the output/load circuit as the single-wire ground
point.
The exact location of the “best” d-c ground point is entirely dependent upon the specific applica-
tion, and its selection requires a combination of analysis, good judgement and some amount of
empirical testing. If there is a choice in selecting either the positive or negative output of the
power supply for the d-c ground point, both sides should be tried, and preference given to the
ground point producing the least noise. For single, isolated loads the d-c ground point is often
best located directly at one of the output terminals of the power supply; when remote error sens-
ing is employed, d-c ground may be established at the point of sense lead attachment. In the
specific case of an internally-grounded load, the d-c ground point is automatically established at
the load.
The output binding posts of ABC Power Supplies are d-c isolated (“floating”) from the chassis in
order to permit the user maximum flexibility in selecting the best single point ground location.
Output ripple specifications as measured at the output are equally valid for either side
grounded. Care must be taken in measuring the ripple and noise at the power supply: measur-
ing devices which are a-c line operated can often introduce additional ripple and noise into the
circuit.
There is, unfortunately, no “best” method for interconnecting the load and power supply. Individ-
ual applications, location and nature of the load require careful analysis in each case. Ground-
ing a single point in the output circuit can be of great importance. It is hoped that the preceding
paragraphs will be of some assistance in most cases. For help in special applications or difficult
problems, consult directly with Kepco's Application Engineering Department.
2.7.4 POWER SUPPLY/LOAD INTERFACE
The general function of a voltage- or current-stabilized power supply is to deliver the rated out-
put quantities to the connected load. The load may have any conceivable characteristic: it may
be fixed or variable, it may have predominantly resistive, capacitive or inductive parameters; it
may be located very close to the power supply output terminals or it may be a considerable dis-
tance away. The perfect interface between a power supply and its load would mean that the