KEPCO HSP Series Operator Manual - Manual (Page 20)

2-6
HSPSERIES OPR 050614
Care must be taken in measuring the ripple and noise at the power supply: measuring 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
specified performance at the output terminals would be transferred without impairment to any
load, regardless of electrical characteristics or proximity to each other.
The stabilized d-c power supply is definitely not an ideal voltage or current source, and practical
interfaces definitely fall short of the ideal. All voltage-stabilized power supplies have a finite
source impedance which increases with frequency, and all current-stabilized power supplies
have a finite shunt impedance which decreases with frequency. The method of interface
between the power supply output and the load must, therefore, take into account not only size
with regard to minimum voltage drop, but configuration with regard to minimizing the impedance
introduced by practical interconnection techniques (wire, bus bars, etc.). The series inductance
of the load wire must be as small as possible as compared to the source inductance of the
power supply: error sensing cannot compensate for reactive effects due to this. These dynamic
conditions are especially important if the load is constantly modulated or step-programmed, or
has primarily reactive characteristics, or where the dynamic output response of the power sup-
ply is critical to load performance.
2.7.5 LOAD CONNECTION - GENERAL
Load connections to the HSP power supply are achieved via the bus bars protruding from the
rear panel. The bus bars are each provided with two holes, one 0.34" diameter clearance hole
(for
5
/
16
" UNC threaded fastener) and one #10-32 threaded hole (see Figure 1-4). The threaded
hole is provided for attachment of error sensing leads from the signal connector when local
sense with benchtop operation is desired. Do not connect sense lines using these holes when
using the HSP Power Supply with plug-in rack adapters; instead connect ± sense lines to ± out-
put studs on rack adapter, observing proper polarities: plus to plus, minus to minus.
Load cable or bus bar attachment should use the clearance hole, using a 5 /
16
" UNC nut, bolt
and lockwasher. The use of the proper fastener size and inclusion of a lockwasher are critical to
maintaining intimate contact between the load conductor and output bus bar; Kepco recom-
mends the use of fasteners made of conductive material (brass, phosphor bronze, etc.) to
enhance conductivity; for high current loads (>100A) Kepco recommends the use of Bellville-
style constant tension washers in place of conventional lockwashers.
NOTE
REGARDLESS OF OUTPUT CONFIGURATION, OUTPUT SENSE LINES MUST
BE CONNECTED FOR OPERATION. OBSERVE POLARITIES: THE NEGATIVE
SENSING WIRE MUST BE CONNECTED TO THE NEGATIVE LOAD WIRE, AND
THE POSITIVE SENSING WIRE TO THE POSITIVE LOAD WIRE.