A Simulation Model for Crowbarring Thyristor Devices

1
A Simulation Model for Crowbarring Thyristor
Devices

• By
• Devender Kasturi

2
Advisory Committee

• Major Advisor
• Dr. Albert B. Grubbs.
• Committee Members
• Dr. Vijay Vaidyanathan
• Dr. Monty Smith
• Industrial Representative
• Mr. Phillip Havens

3
Overview

• Introduction
• Definition of terms
• Background of the Problem
• Problem Statement
• Purpose of the study
• Methodology
• Review of Literature

4
Overview

• Research Questions
• Assumptions
• Limitations
• Hypothesis
• Expected Outcomes
• Significance of the study
• Time Line
• Questions and Suggestions

5
Introduction

• Causes for damage of Electronic equipment
• Wear and tear
• Overvoltage
• Overcurrent

6
Overvoltage Overcurrents

• Lightning
• Power line cross
• Conductive spikes
• Inductive spikes

7
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.

8
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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VI characteristics of SIDACtor device
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.

11
Actual Device (P3100) Characteristics
12
Existing PSpice Model (P3100)
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Actual device Vs Existing model

• Overshoot of PSpice model is more than 3 times
  than that of actual devices.
• VT is very high for the PSpice model.

14
Statement of Need

• There is a need for a new PSPICE model of the
  SIDACtor device.

15
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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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.

17
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?

18
Methodology

• Experimental
• First the existing model is built and tested.
• Research will be done and the changes that have
  to be done are identified.

19
Methodology

1. Model is changed and tested for various surge
   events.
2. Repeat steps 2 and 3 until the simulation model
   characteristics are within 10 of that of actual
   device.

20
Review of Literature

• Circuit simulators employ Newtons 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.

21
Review of Literature

• Errors in specifying circuit connectivity,
  component values, or model parameter values often
  cause convergence problems.

22
Review of Literature

• SIDACtors working is similar to that of a
  thyristor except
• No gate current can be applied to the SIDACtor
• SIDACtor is bidirectional

23
Assumptions

• Actual device works properly
• Test equipment works properly

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

25
Limitations

• Resources
• PSPICE software
• Test Equipment

26
Hypothesis

• Null Hypothesis
• The characteristics of the newly developed
  PSpice model and that of actual device differ by
  more than 10.

27
Hypothesis

• Alternative Hypothesis
• The characteristics of the newly developed
  PSpice model and that of actual device differ by
  no more than 10.

28
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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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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Timeline

• April 2003 Review of Literature and current
  model.
• Summer 2003 Experimental Analysis and Report
  Writing
• Fall 2003 Final Report

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Questions Suggestions