This document summarizes a student project to build a three-phase thyristor bridge controlled by a microprocessor. A PIC 16F877 microcontroller was programmed to trigger thyristors at specific firing angles to control the output voltage. Testing showed the bridge could control DC motor speed by varying the firing angle and output voltage. Harmonics in the input current were reduced using passive low-pass filters. Applications include power electronic labs, motor speed control, battery charging, and uninterruptible power systems.

1. AN-NAJAH NATIONAL UNIVERITY
DEPARTMENT OF
ELECTRICAL ENGINEERING
THREE PHASE THYRISTOR BRIDGE
CONTROLLED BY MICROPROCESSOR
PREPARED BY:
NABEEL MASSRI MOUSA NASIEF
INSTRUCTOR :
PROF. MARWAN MAHMOUD
2008/2009
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SIX PULSELEC PRIDGE RECTIFIER:

3. o Six pulse bridge is the most common one .
o It can be use to control the speed of DC motors .
o It’s output power could be more than 120KW.
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Advantages

4. o Widely used in three phase dual convertors systems (UPS).
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5. o The thyristors are to be triggered every π / 3 .
o Two quadratic operations is possible .
o Could be used in continuous and discontinuous mode.
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Properties

6. building three phase bridge and make investigations about
Its input and output characteristics
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8.  555 Timer Astable And Monostable Multivibrator
f = 1.44/(C1(R1+2R2)), wherein f is in Hz if R1 and R2 are in mega
ohms and C1 is in microfarads.

9.  Unijunction Transistor Relaxation Oscillator

10.  Pulse transformers

12. o We used the idea of zero cross detector
o We used PIC 16F877 to do the triggering program .
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13. Input voltage
Output voltage

14. START
Thyristor
Read the value of the
Input voltage
If value =0v
Delay =(firing angel(
Output the triggering
pulse
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YY
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15. Triggering at 0 Triggering at 45
Triggering at 90 Triggering at 135

16. We chose the thyristor to work on which is TIC 116.
o 8 A Continuous On-State Current
o 400 V to 800 V Off-State Voltage.
o Max IGT of 20 mA.
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17. The wave forms for continuous operations.
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18. o immediately from the PICimmediately from the PIC

19. o Using Triac Photo Coupler (MOC 3020)Using Triac Photo Coupler (MOC 3020)

20. o Using Transistor Photo Coupler (4N25)

21. o The complete circuit

23. Output voltage form at α= 90˚Output voltage form at α= 60˚
Output voltage form at α= 30˚Output voltage form at α= 0˚

24. Input current form at α= 90˚Input current form at α= 60˚
Input current form at α= 30˚Input current form at α= 0˚

25. Output voltage form at α= 90˚Output voltage form at α= 60˚
Output voltage form at α= 30˚Output voltage form at α= 0˚

26. The load angel could be measured by the following equation:
 Ф= tan-1
(wl/R)
 For example:
If R= 16Ω and L= 50mh then the load angle can be calculated as a
following:
Ф= 44.5
Note :RL load is tested under discontinuous operation because it dose
not affect the shape of output voltage for the continuous
operation.

27. Output voltage form at Ф= 67˚Output voltage form at Ф= 55˚
Output voltage form at Ф= 36˚
˚
Output voltage form at Ф= 25˚

28. Input current form at Ф= 67˚Input current form at Ф= 55˚
Input current form at Ф= 36˚
˚
Input current form at Ф= 25˚

29. o The bridge could be used to control the speed of DC motorThe bridge could be used to control the speed of DC motor
Connected to its output terminal by changing the output voltageConnected to its output terminal by changing the output voltage
Which depend on the firing angleWhich depend on the firing angle

30. Output voltage form at α= 90˚Output voltage form at α= 60˚
Output voltage form at α= 30˚Output voltage form at α= 0˚

31. Input current form at α= 90˚Input current form at α= 60˚
Input current form at α= 30˚Input current form at α= 0˚

33.  The input current contains high frequencies
 These frequencies has badly effects on the electrical network
 These frequencies has badly effects on the communication devices
 Removing these harmonics is capable by using filters
 These harmonics are given by:
 Hvd=6,12,18,24,30,………
 Fde=300,600,900,1200,1500…………

34.  Using LC resonance circuit
 Practically the values of L and C are not available in our
market because we need to use non polar capacitor with high
capacity and high voltages, also we face problems in finding
the suitable value of inductors.

35.  Using low pass filter circuit
 Using polar capacitors for large capacity with high voltage
rating .
 The input current form improved .

36. Input current form at fc=318Input current form at fc=500
Input current form at fc= 636Input current form at fc=1590

37. Applications:
 1-Power electronic lab unit
 2- DC motor speed controller
 3-Battery charger
 4- Part of uninterrupted power system(UPS).
Discussion and conclusionDiscussion and conclusion

38. benefits:
 Improve our skills in designing electronic circuits and
interfaces by using the simple electronic components (resistors,
capacitors, transformers and diods), and more complicated
components like photo couplers.
 Learn how to use the measurement devices and how to take
accurate measurement by using multimeter and oscilloscope .
 Have a basic idea about how to use microprocessor (PIC),
building its basic and program it successfully.
 Have a good acknowledgment about the basic power
electronics component (thyristor).
 Understanding the concepts of power electronic like triggering
(firing angel), thyristor turn

39. Future suggestions :
 Varying the firing angle of the thyristor of this circuit by
using potentiometer (this need high level of calibration for the
thyristor firing angle with the PIC analog to digital by
programming ).
 Using this circuit in industrial application but for huge
applications the thyristor should be changed to be more
suitable and stand with high currents.
 Use this circuit to build a complete uninterrupted power
system ( UPS) .