1. A Simulation Model for Crowbarring Thyristor DevicesBy
Devender Kasturi

2. University of North Texas
Advisory Committee
Major Advisor
Dr. Albert B. Grubbs.
Committee Members
Dr. Vijay Vaidyanathan
Dr. Monty Smith
Industrial Representative
Mr. Phillip Havens
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University of North Texas

3. University of North Texas
Overview
Introduction
Definition of terms
Background of the Problem
Problem Statement
Purpose of the study
Methodology
Review of Literature
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University of North Texas

4. University of North Texas
Overview
Research Questions
Assumptions
Limitations
Hypothesis
Expected Outcomes
Significance of the study
Time Line
Questions and Suggestions
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5. University of North Texas
Introduction
Causes for damage of Electronic equipment:
Wear and tear
Overvoltage
Overcurrent
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6. Overvoltage & Overcurrents
Lightning
Power line cross
Conductive spikes
Inductive spikes
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7. University of North Texas
Definition of Terms
VDRM : Peak Standoff voltage across the device in the off condition.
IDRM : Maximum value of leakage current at VDRM.
VT : Voltage across the device after it has turned on.
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University of North Texas

8. University of North Texas
Definition of Terms
VS : Maximum voltage across the SIDACtor device just before switching on.
IH : Minimum amount of current required to maintain the device in the on state.
Surge waveform(ex: 10x700sec)
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9. VI characteristics of SIDACtor device
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10. Background of the Problem
The SIDACtor® device
Characteristics of actual model
Existing SPICE model
Comparison of actual device and existing PSpice model for a 10x700us surge.
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University of North Texas

11. Actual Device (P3100) Characteristics
Overshoot = (app) 300V
VT = (app) 3.5V
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12. Existing PSpice Model (P3100)
Overshoot = 1.01 KV
VT = 100V
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13. Actual device Vs Existing model
Overshoot of PSpice model is more than 3 times than that of actual device’s.
VT is very high for the PSpice model.
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14. University of North Texas
Statement of Need
There is a need for a new PSPICE model of the SIDACtor device.
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University of North Texas

15. University of North Texas
Problem Statement
The problem is the characteristics of the actual device and that of the existing simulation model do not match.
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University of North Texas

16. University of North Texas
Purpose of the Study
To develop a PSpice model by modifying the existing PSpice model or
To develop a new PSpice model.
Test the newly developed model for various surge waveforms.
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University of North Texas

17. University of North Texas
Research Questions
Will the new simulation model have the same characteristics as that of actual device?
How reliable is the PSpice simulation software?
What is the range of operating temperature for the device?
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18. University of North Texas
Methodology
Experimental
First the existing model is built and tested.
Research will be done and the changes that have to be done are identified.
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19. University of North Texas
Methodology
Model is changed and tested for various surge events.
Repeat steps 2 and 3 until the simulation model characteristics are within 10% of that of actual device.
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20. University of North Texas
Review of Literature
Circuit simulators employ Newton’s method to solve the nonlinear systems of equations that are formed during DC and transient analysis.
Convergence problems can occur due to poor starting points defined for the simulation.
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University of North Texas

21. University of North Texas
Review of Literature
Errors in specifying circuit connectivity, component values, or model parameter values often cause convergence problems.
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22. University of North Texas
Review of Literature
SIDACtor’s working is similar to that of a thyristor except:
No gate current can be applied to the SIDACtor
SIDACtor is bidirectional
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23. University of North Texas
Assumptions
Actual device works properly
Test equipment works properly
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24. Equation for Current through the thyristor:
Where Ico1 and Ico2 are leakage currents from collector to base and 1 and 2 current amplification factors
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25. University of North Texas
Limitations
Resources
PSPICE software
Test Equipment
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26. University of North Texas
Hypothesis
Null Hypothesis
The characteristics of the newly developed PSpice model and that of actual device differ by more than 10%.
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27. University of North Texas
Hypothesis
Alternative Hypothesis
The characteristics of the newly developed PSpice model and that of actual device differ by no more than 10%.
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28. University of North Texas
Expected Outcomes
The newly developed PSpice model will exhibit a lower overshoot.
The newly developed PSpice model will exhibit a lower VT value.
The newly developed PSpice model successfully clears all the tests.
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29. Significance of the Study
The simulation model is used for tests rather than the actual device allowing any modifications under considerations to be tested.
Eventually expedites prototype testing.
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30. University of North Texas
Timeline
April 2003 – Review of Literature and current model.
Summer 2003 – Experimental Analysis and Report Writing
Fall 2003 – Final Report
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31. Questions & Suggestions
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