2. CONTENTS
1. Introduction
2. Block Diagram
3. Principle of operation
4. Mode of operation
5. Four quadrant operation
6. Ideal Dual Converter
7. Types of Dual converter
8. Applications of dual converter
3. INTRODUCTION
• It is an electronic converter or circuit which comprises of two
converters.
• One will perform as rectifier and the other will perform as inverter.
• Therefore, we can say that double processes will occur at a moment.
• Here, two full converters are arranged in anti-parallel pattern and
linked to the same dc load.
5. Principle Of Operation
• A.C input given to converter 1 for rectification.
• In this process positive cycle of input is given to first set of forward
biased thyristors which gives a rectified D.C on positive cycle, as well
negative cycle is given to set of reverse biased thyristors which gives a
D.C on negative cycle completing full wave rectified output can be
given to load.
6. Modes of Operation of Dual Converter
• There are two functional modes:
1. Non-circulating current mode.
2. Circulating mode.
7. Non Circulating Current Mode
• One converter will perform at a time. So there is no circulating
current between the converters.
• During the converter 1 operation, firing angle (α1) will be 0<α1< 90o;
Vdc and Idc are positive.
• During the converter 2 operation, firing angle (α2) will be 0<α2< 90o;
Vdc and Idc are negative.
8. Circulating Current Mode
• Two converters will be in the ON condition at the same time. So
circulating current is present.
• The firing angles are adjusted such that firing angle of converter 1 (α1)
+ firing angle of converter 2 (α2) = 180o.
• Converter 1 performs as a controlled rectifier when firing angle be
0<α1< 90o and Converter 2 performs as an inverter when the firing
angle be 90o<α2< 180o. In this condition, Vdc and Idc are positive.
10. Ideal Dual Converter
• The term ‘ideal’ refers to the ripple free output voltage.
• For the purpose of unidirectional flow of DC current, two diodes
(D1and D2) are incorporated between the converters.
• However, the direction of current can be in any way. The average
output voltage of the converter 1 is V01 and converter 2 is V02.
• To make the output voltage of the two converters in same polarity
and magnitude, the firing angles of the thyristors have to be
controlled.
12. • Average output voltage of Single-phase converter =
• Average output voltage of Three-phase converter =
• For converter 1, the average output voltage,
• For converter 2, the average output voltage,
• Output voltage,
13. Types of Dual Converters
• They are of two types:
1. Single-phase dual converter.
2. Three-phase dual converter.
16. Application of Dual Converter
• Direction and Speed control of DC motors.
• Applicable wherever the reversible DC is required.
• Industrial variable speed DC drives.
18. Content
• Introduction to Cyclo-Converters
• Working Principle
• Types of Cycloconverters
• Applications of Cycloconverter
19. Introduction to Cyclo-Converters
• Device that converts AC power of certain frequency to AC power of
another frequency (usually lower frequency).
• Also called as frequency changer.
20. • Cyclo-converters are constructed using naturally commutated
thyristors with capability of bidirectional power flow.
• The principle of the cyclo-converter is described below by using
single-phase to single-phase cyclo-converter.
• Control circuit implementation is not simple because large number of
SCRs, typically 4 or 8 SCRs for single phase and 36 for three- phase
supply.
• For such controller, a microcontroller or microprocessor or DSP is
used to trigger SCRs.
22. Types of Cycloconverters
Mainly there are two types according to the mode of operation which
are showing below
1. Blocking mode Cycloconverters
2. Circulating current Cycloconverters
23. 1. Blocking Mode Cycloconverters
• During the negative load current, the negative converter will provide
the necessary voltage and at that time, the negative converter will be
in the blocked condition. This type of operation is known as blocking
mode operation and the converters which use this method of
operation are termed as blocking mode cycloconverters.
• No need of intergroup reactors because only one converter is working
at a time.
• Cost and size is low.
24. 2. Circuiting Current Cycloconverter
Mainly there are two types according to the output frequency which
are showing below
• Step-up cycloconverters
• Step-down cycloconverters
25. Step-up Cycloconverters
• It provide output having the frequency greater than the input
frequency by using line commutation.
26. Step-down Cycloconverters
• Provides output having lower frequency than the input frequency by
using forced commutation.
• These types of converters are further classified into following:
1) Single-phase to single-phase cyclo-converters
2)Three-phase to single-phase cyclo-converters
3)Three-phase to three-phase cyclo-converter
27. Single phase to Single phase Cycloconverters
• Principles of Cycloconverters can be explained by using single phase
to single phase cycloconverter.
28. Three-Phase to Single-Phase Cycloconverters
• Converter can operates in four quadrants (+V, +I, -V, -I) in two modes
(inverting and rectifying).
29. Three Phase to Three Phase Cycloconverters
• Mainly used in machine drive systems running three-phase
synchronous and induction machines.
30. Applications of Cycloconverter
• Cement mill drives.
• Rolling mills.
• Ship propulsion drivers.
• Water pumps.
• Washing machines
• Mine winders.
• Industries.
