43 Frequency Converters Intermediate circuit The intermediate circuit can function in three diff erent ways, as shown in Fig. 2.3 Main component topologies Intermediate circuit: • Conversion of the rectifi er voltage into a DC voltage • Stabilisation or smoothing of the pulsating DC voltage to make it available to the inverter Inverter Conversion of the constant DC voltage of the rectifi er into a variable AC voltage. The inverter generates the frequency of the motor voltage. Alternatively, some inverters may additionally convert the constant DC voltage into a variable AC voltage. See Fig. 2.3 Main component topologies Inverter.
Control circuit The control circuit transmits signals to – and receives signals from – the rectifi er, the intermediate circuit and the inverter. The design of the individual FC determines specifi cally which parts are controlled. 1 2 Single fase 3 4 Rectifier Inverter Intermed. circuit Un-controlled Triple fase Semi-controlled Fully controlled “Active Front End” Variable Constant 5 6 7 8 9 10 Fig. 2.3 Main component topologies