1. Power Semiconductor Systems II
Author: Ales Havel
Phone number: 4287
Headquarters: E227
Web page:
Power Semiconductor Systems II

2. 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

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

4. 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

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

6. 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

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

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

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

10. Thank You for your attention