Power Electronics-A Continuing Challenge

The age of power semiconductors began when thyristors made their first appearance. They gradually replaced the saturable inductors that were used so far for switched power conversion. The problems related to the nonlinearities of magnetic amplifiers were then easily overcome by naturally commutated thyristor converters. Even so, constructing a line-controlled thyristor converter was still a laborious task. Implementing a current control ler, for instance, required us to design and assemble an analog signal amplifier using many discrete transistors, those novel electronic components. Offset and drift of an amplifier varied with temperature, requiring repeated manual adjustments. Little did we know about parasitic capacitances or stray inductances. Hence, what was meant to be a dc amplifier tended to operate as a high-frequency oscillator.