Power Semiconductor Systems II Author: Ales Havel E-mail: ales.havel@vsb.cz Phone: 5937 Office: EA333 Web: http://homen.vsb.cz/~hav278/ Power Semiconductor Systems II

Content of the presentation Main types of frequency converters AC-DC converters DC-DC converters DC-AC converters AC-AC converters Direct frequency converters Cycloconverters Indirect frequency converters Converters with voltage type of the DC link Converters with current type of the DC link

Power converters A power semiconductor converter is an electrical device for converting electrical energy.

Cycloconverters Characteristics: Creation of output AC voltage without the need of DC link Output frequency is always lower than the input frequency Large number of thyristors (36 for 3 phase cycloconverter) but relatively low switching power losses Relatively complex control due to large number of switches Non-sinusoidal consumption of mains current, therefore large consumption of reactive power and wide spectra of harmonics Wiring diagram of one phase of total three-phase cycloconverter

Cycloconverters Principal block wiring topologies of three-phase cycloconverters Without common node With common node

Cycloconverters Utilization of cycloconverters: Low speed three-phase synchronous motors with field windings High power low speed drives with relatively low demands on dynamics Principal of creation of output voltage and current

Cycloconverters – load waveforms Output frequency: 25Hz Load parameters: R = 7Ω, L = 10mH Control parameters: alpha = 0°

Cycloconverters – load waveforms Output frequency: 25Hz Load parameters: R = 7Ω, L = 10mH Control parameters: alpha = 30°

Cycloconverters – load waveforms Output frequency: 25Hz Load parameters: R = 7Ω, L = 50mH Control parameters: alpha = 0°

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