44 Frequency Converters Confi guration of the FC involves selection between diff erent main components. See table 2.1 Frequency converter confi guration examples. Table 2.1 Frequency converter confi guration examples What all FC’s have in common is that the control circuit uses signals to switch the inverter semiconductors on and off . This switching pattern is based on a variety of principles. FC’s can further be broken down into types according to the switching pattern that controls the supply voltage to the motor. 2.3 Rectifi er Depending on the power involved, the power supply takes the form of a three- phase AC voltage or a single-phase AC voltage with a fi xed frequency. For example:
Three-phase AC voltage: 3 x 400 V/50 Hz Single-phase AC voltage: 1 x 240 V/50 Hz The rectifi er of a FC consists of diodes or thyristors, a combination of both, or bipolar transistors (IGBTs). Fig. 2.3 Main component topologies shows the four diff erent rectifi cation approaches that are available today. In low-power applications (up to 30 kW, depending on the manufacturer), uncontrolled B6 bridge rectifi ers are generally used. Half-controlled rectifi ers are used in the power range 37 kW and above. The rectifi er circuits described above allow energy to fl ow in one direction, from the supply to the intermediate circuit. Conf iguration example Abbreviation Conf iguration:
Reference to components in Fig. 2.3 Pulse amplitude modulated converter PAM 1 or 2 or 3 and 6 and 9 or 10 Pulse width modulated converter PWM 1 or 2 or 3 or 4 and 7 or 8 and 9 or 19 Current-source converter CSI 3, 5, and 9