Читать книгу Handbook of Large Hydro Generators - Geoff Klempner - Страница 24

The fourth and final physical law that captures, together with the previous three, all the physical processes occurring inside an electric machine, is the “principle of energy conversion.” Within the domain of the electromechanical world of an electric rotating machine, this principle states that

All the electrical and mechanical energy flowing into the machine, less all the electrical and mechanical energy flowing out of the machine and stored in the machine, equals the energy dissipated from the machine as heat.

It is important to recognize that although mechanical and electrical energy can go into or out of the machine, the heat generated within the machine always has a negative sign, that is, heat generated in the machine is always released during the conversion process. A plus sign indicates energy going in; a minus indicates energy going out. In the case of the stored energy (electrical and mechanical), a plus sign indicates an increase of stored energy, whereas a minus sign indicates a reduction in stored energy.

Figure 1.5-4 Principle of energy conversion as applicable to electric rotating machines.

The balance between the various forms of energy in the machine will determine its efficiency and cooling requirements, as well as its critical performance and construction parameters. Figure 1.5-4 depicts the principle of energy conversion as applicable to electric rotating machines.