Week 8 AC-to-AC Converters 1

Single-phase AC Voltage Controller 2

3 Thyristor/Triac

4 Single-Phase AC-AC Converter

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Operation of a Single-phase AC Voltage Controller with (a) Single- pulse Gate Signal, (b) Multi-pulse Gate Signal 9

Definition of a Control Angle 10

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Fully Controlled Three-phase AC Voltage Controller 12

Thyristor Gate Triggering Generation of the firing signal The sawtooth waveform (synchronized to the ac input) is compared with the control signal v control, and the delay angle a with respect to the positive zero crossing of the ac line voltage is obtained in terms of v control and the peak of the sawtooth waveform V st.

Full-Bridge (Single- and Three- Phase) Thyristor Converters

Voltage and Current Distribution in a Fully Controlled Three-phase AC Voltage Controller: (a) Two Triacs Conducting, (b) Three Triacs Conducting 15

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Polarities of Output Voltages and Currents in a Fully Controlled Three-phase AC Voltage Controller in Mode 2 Before Firing Triac TA (solid line) and Following the Firing (broken line) 17

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Three-phase AC Voltage Controllers Connected Before the Load: (a) Half- controlled, (b) Delta-connected 21

Three-phase AC Voltage Controllers Connected After the Load: (a) Wye- Connected, (b) Delta-connected 22

Three-phase Four-wire AC Voltage Controller 23

Single-phase AC Chopper with an Input Filter 24

Waveforms of Voltages and Currents in a Single-phase AC chopper: (a) Output Voltage and Current, (b) Input Voltage and Current After the Input Filter, and the Fundamental Output Current 25

Control Characteristic of an AC Chopper 26

Wye-connected Three-phase AC Choppers: (a) Three-wire, (b) Four Wire 27

Delta-connected Three-phase AC Chopper 28

Changes in the Firing Angle in a Cycloconverter 29

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Three-phase Three-pulse Cycloconverter 31

Three-phase Six-pulse Cycloconverter with Isolated Phase Loads 32

Three-phase Six-pulse Cycloconverter with Interconnected Phase Loads 33

Three-phase to Three-phase (3  -3  ) Matrix Converter 34

Arrangement of 3  -1  and 1  -3  Matrix Converters, Equivalent to a 3  -3  Matrix Converter 35

State AAB as Realized by Activation of Switches in (a) Virtual Rectifier and Inverter, (b) Matrix Converter 36

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Reference Current Vector in the Vector Space of input Currents of the Virtual Rectifier 39

Reference Voltage Vector in the Vector Space of Line-to-Neutral Output Voltages of the Virtual Inverter 40

Bidirectional Semiconductor Power Switches: (a) Two IGBTs and Two Diodes, (b) One IGBT and Four Diodes 41

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Switching Signals for Individual Switches in a Matrix Converter 43

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45 Switching Characteristics

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