41 Frequency Converters 2 Frequency Converters Since the late 1960s, the FC has developed at a tremendous rate. Major advances have been made thanks to developments within the fi elds of microprocessor and semiconductor technology, in particular, and the associated price reduction. However, the basic principles of the FC remain the same. As stated in the introduction, the main function of a FC is to generate a variable supply (for example, 0 to 400 V / 0 to 50 Hz) from a supply with “fi xed” parameters (for example, 400 V and 50 Hz). There are two approaches to performing the conversion, defi ning two types of FC’s: Direct converters and converters with intermediate circuit.
Frequency Converters Converters with intermediate circuit Direct converters Variable Constant PWM CSI PAM Current-source frequency converters I-converters Voltage-source frequency converters U-converters CSI: Current Source Intverter PAM: Pulse Amplitude Modulation PWM: Pulse Width Modulation Fig. 2.1 Overview of frequency converter types 2.1 Direct Converters The direct converter performs the conversion with no intermediate storage. Direct converters are generally only used in high-power applications (megawatt range). This book does not deal with this type of converter in detail, but several features are worth mentioning.