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.