Power semiconductor devices

Abstract

All a.c. and d.c. drives use power semiconductor devices to convert and control electrical power. This section reviews important characteristics of the most conventional power devices in drives applications. It is common to operate semiconductor devices in switched mode operation. This mode of operation implies that the device is either fully on or fully off, and power dissipation is therefore low compared to that encountered in the linear mode of operation. It is this feature that makes switched mode operation the key to achieving high efficiency. The practically important power semiconductor devices in relation to motor drives are diodes, thyristors (also called the silicon controlled rectifier, SCR), the triode thyristors (Triac), the gate turn-off thyristors (GTO), the integrated gate commutated thyristors (IGCT), the metal-oxide semiconductor field-effect transistors (MOSFET), the insulated gate bipolar transistors (IGBT), and the bipolar junction transistors (BJT) (although this device has largely been superseded by the other devices ). Power switching devices require electronic 'gate drive' circuits for turning the device on and off. These, called 'driver circuits', are in general complex and also include protection features such as over-current protection. For this reason, details of these circuits have for the most been part limited to a description of the requirements to gate the devices.