Primary ground

Figure 11-11 Two Safety-approved Y-capacitors from Primary Ground to Protective Earth to Help Complete the CM Noise Loop Close to the Power Stage...

In high-voltage applications (e.g. off-line power supplies), it may in fact be required by law, to provide electrical isolation between a hazardous input voltage level and user-accessible ( safe ) output terminals of the power supply. Therefore there is a primary ground at the input side of the transformer, and a separate secondary ground on the output side. 

Note In off-line power supplies, for better EMI suppression, we may decide to place Y-caps from the rectified dc rails (either one or both) to earth. So sometimes we place Y-caps from primary ground to secondary ground (usually connected to earth ground), or from the HVDC (high voltage dc) rail to secondary ground. In either of these positions, a Y1 capacitor (or two Y2 capacitors in series) may be required. 

The entire loop of the PCB traces (up to the input side) as shown in Figure 11-4 needs to be thick and short. Unfortunately, this often tends to be necessarily long, considering board layout constraints, and all the other components that need to be mounted on it. So in that case we can provide a high frequency decoupling capacitor from the HVDC to primary ground, very close to the mosfet. 

Tip We don t need to draw any current at all from this Faraday winding to make it work. So it need not even be required by our circuitry (for an auxiliary rail). In that case, we could just wrap a few turns of thin wire (spread out evenly), with one end of it connected to primary ground, and the other end via a small 22 pF capacitor to primary ground. This technique certainly saves production costs associated with the making and placing of a formal Faraday shield — not to mention the improvement in efficiency due to the reduced leakage inductance (as compared to what a formal Faraday shield may lead to). In that sense, this informal Faraday shield is a very useful idea, certainly worth trying out. 

VT DEC. 1999b. Primary ground water quality standards. Vermont Agency of Natural Resources, Department of Environmental Conservation, Water Quality Division. Chapter 12, Appendix One. 

Before implementing a Ufer ground system, consult a qualified contractor. Because the Ufer ground system will be the primary grounding element for the facility, it must be done correctly. 

In both systems Rentzepis and coworkers(and also Monger et al., for rhodopsin ) failed to observe the ultrafast repopulation process of the primary ground state pigment. Given the significant quantum yields for ground state repopulation, it should thus be concluded that this process is completed within times which are shorter than the 6 psec resolution time of the above measurements. 

As the nation s primary ground combat force, the Army must be capable of conducting prompt and sustained operations in all types of terrain and operating environments, across the entire spectrum of conflict. Intensive and realistic field... 

Slope Stability The primary ground control concern in surface mines is slope stability, and the handling of unstable slopes when they occur. Generally it is not a problem because of good mine design and operational practices, but when wet conditions occur in a mine, once-stable slopes can become unstable. The methods for designing and maintaining stable slopes will be covered briefly in the section on control of hazards. 

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