Pontifical Catholic University of the Rio Grande do SulPontifical Catholic University of the Rio Grande do Sul

BrazilBrazil

Didactic Platform for Study of AC-AC

Converters

Dos Reis, F. S.; Lima, J. C.; Fuentefria, F. B. Dos Reis, F. S.; Lima, J. C.; Fuentefria, F. B.

Table of Contents

INTRODUCTIONINTRODUCTION

BLOCK DIAGRAMBLOCK DIAGRAM

OBJECTIVEOBJECTIVE

COMMAND AND POWER CIRCUIT COMMAND AND POWER CIRCUIT

SOURCE AND ZERO DETECTORSOURCE AND ZERO DETECTOR

CONTROL CIRCUITCONTROL CIRCUIT

EXPERIMENTAL RESULTSEXPERIMENTAL RESULTS

CONCLUSIONSCONCLUSIONS

INTRODUCTION

The didactic platform to study AC-AC

converters, is composed by three basic stages:

The command and power circuit integrated;

Source and main’s zero detector circuit for

system synchronism;

Control circuit based on a microcontroller.

OBJECTIVEOBJECTIVE

The main objective of this paper is to relate the development of a flexible didactic platform to study the AC-AC converter, looking for to propitiate with this system a better understanding of the operation of AC-AC converters through a practical experience.

BLOCK DIAGRAM

Motor

Vcc

Start Stop

Isolation

µC

Thyristor

Zero Detector

Time Base

RS-232

COMMAND AND POWER CIRCUIT - 1

The command signals are applied in the The command signals are applied in the power stage using optocouplers, power stage using optocouplers, isolating it from the control circuit ;isolating it from the control circuit ;

The power stage is contituted by six The power stage is contituted by six thyristors antiparallel connected;thyristors antiparallel connected;

This arrangement may be used as a This arrangement may be used as a three-phase AC-AC converter or like three-phase AC-AC converter or like three single-phase AC-AC converter, three single-phase AC-AC converter, which may be independently controlled.which may be independently controlled.

COMMAND AND POWER CIRCUIT - 2

X5

TIC 126

213

J3

Phase B

12

R7

330

R9

330

R2

390

X3

TIC 126

213

J1

Input

1234

D41N4007

21

Vcc

R8

390

X6

TIC 126

21

3

X7

TIC 126

213

R3

330

R6

330

Vcc

J4

Phase C

12

D21N4007

21

X8

TIC 126

21

3U3MOC3023

1

2

64

R10

470

Vcc

R11

470

R12

470

R1

330

D1

1N4007

21

D3

1N4007

21

J2

Phase A

12

U2MOC3023

1

2

64

R5

390

U1MOC3023

1

2

64

D61N40072

1

Vcc

D5

1N4007

21

R4

330

X4

TIC 12621

3

SOURCE AND ZERO DETECTOR - 1

This stage was elaborated with the This stage was elaborated with the utilization of a step down transformer utilization of a step down transformer 110/220V to 12V, used in the power 110/220V to 12V, used in the power supply and in the zero detector circuit;supply and in the zero detector circuit;

In each main cycle two pulses are In each main cycle two pulses are generated, each one in the beginning of generated, each one in the beginning of each half cycle;each half cycle;

The microcontroller receives these The microcontroller receives these pulses, which are used as time reference pulses, which are used as time reference for the thyristor command.for the thyristor command.

SOURCE AND ZERO DETECTOR - 2

D2

1N4005

1 2

R41k

SW1

21

3

D4

LED

1 2

J2

Output

123

R3

1k

C12200u

1

2

R110k

D1

1N4005

1 2T1

Trafo 110/220 - 12+12

1 4

5

3 6

2R210k

J1

Input

12

Q2

BC548B

U2LM7805C/TO3

1 3

2

IN OUT

GN

D

R5

470

Q1

BC548B

F1

D3

1N4005

1 2

CONTROL CIRCUIT - 1

The control is made using the phase The control is made using the phase angle control;angle control;

An 8051 Atmel AT89C52 was used to An 8051 Atmel AT89C52 was used to control the system;control the system;

The microcontroller receives the The microcontroller receives the synchronism information by the zero synchronism information by the zero detector and processes it, giving the detector and processes it, giving the proper thyristors phase angle and proper thyristors phase angle and generates the pulses for the thyristors generates the pulses for the thyristors appropriately;appropriately;

CONTROL CIRCUIT - 2

The ON/OFF control and the Softstart for The ON/OFF control and the Softstart for AC motors were also implemented in this AC motors were also implemented in this platform; platform;

To implement this circuits, the control To implement this circuits, the control needs to temporize the zero detector needs to temporize the zero detector pulses using interruptions;pulses using interruptions;

A PC may program several positive or A PC may program several positive or negative acceleration curves, obtained negative acceleration curves, obtained through the continuous phase angle through the continuous phase angle variations;variations;

CONTROL CIRCUIT - 3

The platform can operate autonomously The platform can operate autonomously or have its program changed directly or have its program changed directly though a PC using its RS-232 serial though a PC using its RS-232 serial interface; interface;

For autonomous operation the plataform For autonomous operation the plataform incorporates a display and a small incorporates a display and a small keyboard that allows programming the keyboard that allows programming the parameters.parameters.

CONTROL CIRCUIT - 4

EXPERIMENTAL RESULTS - 1

For a didactic classroom use of the For a didactic classroom use of the platform a simple load assembly using platform a simple load assembly using incandescent light bulbs was made; incandescent light bulbs was made;

The three The three

phase phase thyristors had thyristors had been tuned on been tuned on correctly; correctly;

EXPERIMENTAL RESULTS - 2

The voltage and current in the loads can The voltage and current in the loads can be easily measured with the aid of a be easily measured with the aid of a multimeter and an oscilloscope ; multimeter and an oscilloscope ;

Full Full developed developed didactic didactic platform.platform.

CONCLUSIONS - 1

This work is inserted in the context of a This work is inserted in the context of a solid pedagogic proposal for the Power solid pedagogic proposal for the Power Electronics teaching, based on the Electronics teaching, based on the theoretical practical experience mainly in theoretical practical experience mainly in the field of the AC converters; the field of the AC converters;

The system now presented is inserted in The system now presented is inserted in a wider proposal, started with a didactic a wider proposal, started with a didactic kit family, elaborated for the study of kit family, elaborated for the study of rectifiers circuits and inverter circuits;rectifiers circuits and inverter circuits;

CONCLUSIONS - 2

After the implementation of these kits an After the implementation of these kits an expressive improvement of the learning expressive improvement of the learning process was observed, obtaining high process was observed, obtaining high approval indexes different from what approval indexes different from what happened when the discipline was happened when the discipline was presented in the traditional way; presented in the traditional way;

CONCLUSIONS - 3

We would like to remark the importance We would like to remark the importance of the popularization of this kind of work, of the popularization of this kind of work, that approaches pedagogic aspects and that approaches pedagogic aspects and is concerned with the formation of a new is concerned with the formation of a new methodology of teaching the Power methodology of teaching the Power Electronics disciplines;Electronics disciplines;

CONCLUSIONS - 4

The versatility of the platform and great The versatility of the platform and great economy obtained in relation to the economy obtained in relation to the available educational kits found on the available educational kits found on the market are additional advantages of the market are additional advantages of the proposed system.proposed system.