BOP HIPWR 031912 2-9One of the most important considerations in establishing a successful grounding scheme is toavoid GROUND LOOPS. Ground loops are created when two or more points are grounded atdifferent physical locations along the output circuit. Due to the interconnection impedancebetween the separated grounding points, a difference voltage and resultant current flow issuperimposed on the load. The effect of this ground loop can be anything from an undesirableincrease in output noise to disruption of power supply and/or load operation. The only way toavoid 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 groundpoint.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 ofempirical testing. If there is a choice in selecting either the OUTPUT or COMMON output termi-nals of the power supply for the d-c ground point, both sides should be tried, and preferencegiven to the ground point producing the least noise. For single, isolated loads the d-c groundpoint is often best located directly at one of the output terminals of the power supply; whenremote error sensing is employed, d-c ground may be established at the point of sense leadattachment. In the specific case of an internally-grounded load, the d-c ground point is automat-ically established at the load.The output and common terminals of BOP power supplies are d-c isolated (“floating”) from thechassis in order to permit the user maximum flexibility in selecting the best single point groundlocation. Care must be taken in measuring the ripple and noise at the power supply: measuringdevices which are a-c line operated can often introduce additional ripple and noise into the cir-cuit.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 precedingparagraphs will be of some assistance in most cases. For help in special applications or difficultproblems, consult directly with Kepco's Application Engineering Department.2.5.3.1 GROUNDING NETWORK CONFIGURATIONWhen the output is floating there is a tendency for large changes in output voltage to affect thedigital programming section, possibly resulting in an erroneous output. Decoupling capacitorsfrom each of the two output terminals to the chassis via a terminal block link form a groundingnetwork. The grounding network is designed to reduce high frequency noise and ensure that thedigital programming section is not adversely affected by the dynamic swing of the output. Thepower supply is shipped with the grounding network connected: a connection between terminalsTB1-4 (GND NET) and TB1-5 (GND). To disconnect the grounding network from the output,remove the connection across TB1-4 and TB1-5.2.5.4 POWER SUPPLY/LOAD INTERFACEThe 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 maybe fixed or variable, it may have predominantly resistive, capacitive or inductive parameters; itmay 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 thespecified performance at the output terminals would be transferred without impairment to anyload, regardless of electrical characteristics or proximity to each other.
