TBC OPR 071019
3-1
SECTION 3 - OPERATING INSTRUCTIONS
3.1
GENERAL
Interconnections between a stabilized Battery Charger Power Supply, and its load are as critical
as the interface between other types of electronic equipment. If optimum performance is
expected, certain rules for the interconnections must be observed by the user. These rules are
described in detail in the following paragraphs.
3.2
DC (OUTPUT) GROUNDING
Connections between the Battery Charger Power Supply and the load Goad and sensing con-
nections) may, despite all precautions such as shielding, twisting of wire-pairs, etc., “pick-up”
radiated noise of a wide frequency spectrum. To minimize these undesired effects, one side of
the Battery Charger Power Supply output/load circuit must be grounded.
Successful DC grounding depends on careful analysis of the individual situation and only gen-
eral guide lines can be provided here. One of the major points, however, is to avoid GROUND
LOOPS. Ground loops are created when two (or more) points are grounded along the output cir-
cuit. Due to the wire impedance between the grounded pOints, a noise voltage is developed
which is superimposed on the load. The only way to avoid ground loops is to investigate the out-
put circuit (including the connected load) with an ohmmeter, for any resistance to ground. A sin-
gle DC ground point can be selected only if the output circuit is completely isolated. A single
point is selected along the Power Supply output/load circuit and this point is returned to ground
with a single wire. The exact location of this “best” DC ground-point is entirely dependent on the
application at hand. For single, isolated loads, the DC ground-pOint may be located directly at
one of the output terminals of the Power Supply which may be connected to ground. If Error
Sensing is employed, DC ground can be established at the remote load. In case of an internally
grounded load, the DC ground is automatically established directly at the load.
3.3
LOAD WIRE SELECTION
A realistic model for a voltage stabilized Battery Charger Power Supply must, for example,
include a series resistance, representing a small DC and low frequency source impedance; in
series with an inductance, representing the source impedance at higher frequencies. This is
because of the variation in the equivalent characteristic output circuit impedance as the fre-
quency changes. Load wire selection should be made with those facts in mind. The load wire
size should not only be selected for minimum voltage drop (Error Sensing, as discussed below,
will take care of that), but also the series inductance of the load wire must be kept as small as
possible compared to the source inductance of the Battery Charger Power Supply (Error Sens-
ing cannot compensate for this).
3.4
LOAD CONNECTION, METHOD 1 (LOCAL ERROR SENSING)
The most basic Battery Charger Power Supply interconnection for maintaining Batteries con-
nected across a load consists of 2-wire connection from the rear output terminals. The load
leads should be tightly twisted to reduce “pick-up” from stray magnetic fields.
Figure 3-1 shows the correct and incorrect methods of connecting single and multiple loads with
local sensing. Remote Sensing should be used for the most critical load (see PAR. 3.5). Local
error sensing links must be connected with the proper poS to +M and –S to –M. The TBC
Battery Charger Power Supplies are shipped with links (jumpers) that connect the Sensing ter-
minals directly to the Monitor terminals. These links should be removed when remote sensing is
employed.
