Title: Lesson
Course: Electronics Theory (IC 102-IC 102) > Section: Web Content

Industry uses different types of  high powered electronic switches and devices to shape wave forms called Thyristors, so this week those devices will be covered. You'll start out with the Shockly diode to get an understanding of how the device turns on (breakover voltage) and how it is turned off (holding current). The Shockly then can be modified into the SCR where the device can be controlled by pulsing the gate. Since both these devices are only unidirectional devices something to control current in both directions of the AC cycle will be needed, so you'll be studying Diacs and Triacs which are bidirectional switches. Understanding how these devices are triggered on and how they are shut off are imperative, and understanding the characteristic curves should make that easier. Learning how to troubleshoot the SCR and Triac in the field with an Ohmmeter can very be helpful, so you should get familiar with that. UJT's have more precise control in triggering a SCR's gate circuit, so understanding their characteristics are important. The IGBT is strictly a voltage controlled, high current, fast switching device by design. Since these are strictly on and off devices be sure to focus on what it takes to turn "on" and shut "off" each of these devices.
Reading Assignment:
Volume 3 Chapter 2 Solid-State Device Theory (Junction Field-Effect Transistors, Insulated Gate Field Effect Transistors, and Thyristors) http://www.ibiblio.org/kuphaldt/electricCircuits/Semi/SEMI_2.html
Volume 3 Chapter 7 Thyristors (All but Optothristors and Field-Effect-Controlled Thyristors) http://www.ibiblio.org/kuphaldt/electricCircuits/Semi/SEMI_7.html
Electrical Motor Controls for Integrated Systems - Chapter #13 (pgs 390-394; 400-407)
Industrial Control Electronics: Devices, Systems, & Applications - Chapter #3  Tyristors (pgs 45-66)
The power points for this weeks topic are in the Handout section for your viewing.
The videos contain more explanation of the topics this week and can be found below, be sure to check them out.
This week in the Coursework tab there is a worksheet and a lab experiment to be completed. The worksheet deals with testing different Thyristors with an ohmmeter and being able to determine their state. The lab experiment is firing and turning off a load with a DC source, on the AC side we are looking at firing the load at different parts of the cycle. The load here is a lamp but remember the load could just as easily be a motor.
For the topic this week I thought it might be fun to do a little brainstorming, so be sure to go to the Forum page often and be a part of the fun.
This week I would like you to go back to the Solid State Challenge and open the Troubleshooting CE Amplifiers tab and take the troubleshooting challenge. You may do the challenge as many times as you like and turn in your best score for a grade (50%-75% - 5 points, 75% and up - 10 points). This will challenge your understanding of the material discussed last week. The other parts of the software has really good transistor information, check it out if you can find the time.