KEPCO HSP Series Operator Manual - Manual (Page 19)

HSPSERIES OPR 050614
2-5
2.7.2 SOURCE POWER CONNECTIONS
The rear panel of the HSP power supply is equipped with an IEC 320 style recessed power inlet
connector which provides interface to a 3-wire safety line cord via a polarized mating plug.
Kepco offers as accessories (see Table 1-3) both a user-wired mating connector and a prewired
linecord set, the latter configured for North American applications. Terminal assignment follows
internationally accepted conventions (see Figure 2-3). It is the user's responsibility to ensure
that all applicable local codes for source power wiring are met.
The user-wired mating connector requires size #14 AWG (minimum) conductors for all three
connections. When HSP power supplies are installed in a plug-in rack adapter (RA 60 or simi-
lar), consult the rack adapter Instruction Manual for source connection information.
Depending on your application, source branch current rating may be significantly less than the
rating of the HSP circuit breaker, especially in configurations where HSP are used in parallel/
redundant applications. The HSP circuit breaker rating is based on worst-case operating condi-
tions. However, since HSP power supplies are switch-mode power supplies, the source power
drain is constant and essentially independent of source voltage, regardless of load power
requirements. Therefore under normal, rather than worst case, conditions, HSP draw substan-
tially less than the rated maximum input current, particularly at higher source voltages. Contact
Kepco Applications Engineering for additional information.
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
“pick-up”. To minimize the effects of this radiated noise the user should consider grounding one
side of the power supply/load circuit. The success of d-c grounding requires careful analysis of
each specific application, however, and this recommendation can only serve as a general guide-
line.
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 terminals of HSP 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.