4. A vast scientific and technical discipline

Figure 11 illustrates the physical phenomena that an engineer working on a variable speed drive for an electric motor, for example, needs to be aware of. These phenomena are placed in relation to the time constants they generate. So it's a challenge to recall the triptych of interactions between the switching of semiconductor components, their joule losses and EMC electromagnetic compatibility. Switching fast is polluting, because the waveforms, images of electromagnetic emission sources, include steep edges and very high-frequency oscillations. But slower switching generates Joule losses, which means heat has to be extracted, the reliability of semiconductor components is compromised, and the cooling system is more expensive. The cooling system also means that components...