Puestos de trabajo.

...

(1)[pic 35]

Where:

X, es un factor de ajuste para alpha.

, es el ángulo de control de cada thyristor. [pic 36]

Pulso de control para un angulo máximo y minimo. Adjuntar imagen.

F. Stage of Isolation

The stage of isolation is compound for four optocouplers, that fulfill the function of separating the power stage of control stage.

[pic 37]

Fig. 4 Circuit of isolation stage

G. Stage of Power

This stage is compound for the power switches and the load to feed. In this case the devices used as switches are SCR(silicon controlled rectifier).

[pic 38]

Fig. 5 Circuit of power stage

V. RESULT AND DISCUSSION

The strategy of control implemented presented the following results, which fulfills the objective of providing controlled dc output voltage for type different of load.

A. Bridge Rectifier Output for Resistive Load

1) for firing angle, α=30

La figura mustra la forma de onda de salida del rectificador with resistive load and its respective control pulse.

Imagen de salida con el pulso de control, El valor del voltaje de salida promedio es dado en la tabla I

2) for firing angle, α=60

3) for firing angle, α=90

4) for firing angle, α=120

5) for firing angle, α=150

TABLE I AVERAGE OUTPUT VOLTAGE VALUES OF BRIDGE RECTIFIER WITH RESISTIVE LOAD

CONTROL VOLTAGE

FIRING ANGLE, [pic 39]

OUTPUT VOLTAGE

30°

60°

90°

120°

150°

.

B. Bridge Rectifier Output for Motor Load

La figura mustra la forma de onda de salida del rectificador with motor load and its respective control pulse.

Imagen de salida con el pulso de control, El valor del voltaje de salida promedio es dado en la tabla II

1) for firing angle, α=30

2) for firing angle, α=60

3) for firing angle, α=90

4) for firing angle, α=120

5) for firing angle, α=150

TABLE II AVERAGE OUTPUT VOLTAGE VALUES OF BRIDGE RECTIFIER WITH MOTOR LOAD

CONTROL VOLTAGE

FIRING ANGLE, [pic 40]

OUTPUT VOLTAGE

30°

60°

90°

120°

150°

VI.CONCLUSION

The strategy of digital control designed and implemented in this article for the firing control of SCRs in a single phase rectifier fulfilled the objectives proposed. The quantity of electronics elements used in the control of thyristors through the strategy of control presented notably decreased.

It observed the advantage of this strategy in front of the traditional methods of control of thyristors so it obtained the same result but of a manner more practical and cheaper , finally it got a control of phase angle from 0 to 180 grades with linear characteristics.

References

P. S. Bimbhra, “Power Electronics,” Khanna Publishers, 3rd edition pp. 146-152, 2006.

N. Mohan, T. M. Undeland and W. P. Robbins, “Power electronics: Converters, Applications and Design” New York: Wiley, 3rd edition, pp. 126-138, 2006.

R. Simard and V. Rajagopalan, “Economical equidistant pulse Firing scheme for Thyristorized D.C. drives,” IEEE Trans. Ind. Electron. Contr. Instrum., vol. IECI-22, No.3, pp. 425-429, 1975.

S.C.Gupta, K.Venkatesan, And K.Eape, “Generalized Firing Angle Controller Using Phase loop for Thyristor Control, ” IEEE Transactions On industrial Electronics and Control Instrumentation, vol. IECI-28, No. 1, February 1981.

S. Murugesan and C.Kameswara, “Simple adaptative analog and digital trigger circuits for thyristors working under wide range of supply Frequency” IEEE Trans. Ind. Electron. Contr. Instrum., vol. IECI-24, No. 1, pp.46-49, 1977.

Tirtharaj Sen, Pijush Kanti Bhattacharjee and Manjima Bhattacharya, “Design And Implementation Of Firing Circuit For Single- Phase

Converter,” International Journal of Computer and Electrical Engineering, vol. 3, pp. 368-374, June 2011.

Geno Peter, “Design Of Single Phase half Controlled Converter Using Cosine Wave Crossing Control With Various Protections,” International Journal of engineering Science and Technology, vol. 2(9),pp 4222-4227, 2010.

Mukesh Gupta, Sachin Kumar, Vagicharla Karthik, “Design, Fabrication and Testing of cosine control Firing Scheme For Single Phase Half Controlled Bridge Rectifier,” International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering, vol. 2, no. 8,pp.3834-3844,2013.

L.H.Hoang, “A digitally controlled thyristor trigger circuit” Proc. IEEE, vol. 66, No.1, pp. 89-91, Jan. 1978.

R. Arockiasamy and S. Doraipandy, “A novel trigger scheme for Thyristor operating under variable frequency anode supply,” IEEE Trans. Ind. Electron.