As mentioned earlier, a LD is an electrical device that needs a source of electrical energy with the output characteristic of a CCS or CPS for power. This chapter examines the types of available sources.
There are a variety of devices designed to produce and supply electricity to consumers. They transform carriers of nonelectric energy, e.g., from oil, gas, chemical reactions, water, wind, sunlight, etc., into electrical energy (the technical literature refers to them as the “primary sources of electrical energy”). This transformed energy is either direct current (DC) or alternating current (AC).
Most applications of this energy use two types of primary sources: electric batteries (used in mobile objects such as vehicles and flashlights) and AC generators with an associated AC grid (in which the energy from many primary sources is combined to power stationary equipment). There are also mobile generators, which generate electricity with parameters that match an AC grid.
The primary sources of electrical energy can only directly power limited types of electrical devices, such as the incandescent bulbs in flashlights powered by batteries. Some AC motors and incandescent lamps are powered directly from an AC line. Most electrical devices (electrical loads) require either AC sources with a different AC voltage and/or frequency, or DC sources with an output characteristic of a CVS, CCS, or CPS.
This arrangement involves an intermediate device connected between the primary electric source and the load that converts electrical energy from the primary source into electrical energy that has the characteristics needed by the load. These devices are called “secondary sources of electrical energy.” In the American technical literature, they are usually called power supplies (PSs). In relation to powering LDs, secondary sources are identified as LDDs.
An understanding of the characteristics of electrical sources and electrical loads, as well as the interaction between them, is necessary for competent LDD design. One of the primary goals of this book is to present the design principles and characteristics of the secondary sources of electrical energy devoted to powering LDs. The following section considers the characteristics of primary sources.
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