EXPERIMENT IV SILICON-CONTROLLED RECTIFIER DOCX

Title	EXPERIMENT IV SILICON-CONTROLLED RECTIFIER
Author	King Iney
Pages	8
File Size	173.3 KB
File Type	DOCX
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EXPERIMENT IV SILICON-CONTROLLED RECTIFIER I. OBJECTIVE: After completing and performing the laboratory experiment, you will able to: 1. Demonstrate a practical go/no go methods of testing an SCR with ohmmeter. 2. Show the turn-on (fire) and turn-off (reset) methods for an SCR. 3. Determine the electrical characteristics of a particular SCR. 4. Define the various SCR parameters. INTRODUCTION: The PN junction from gate to cathode of an SCR can be tested with an ohmmeter similar to a regular diode. However, testing from anode to gate will not indicate if an SCR is working properly, because one of the PN junctions is always reverse biased. The SCR can be tested with an ohmmeter by placing the positive lead on the anode and the negative lead on the cathode with the gate left open. The meter should read high or infinite resistance. Placing a clip lead from the anode or positive lead of the ohmmeter to the gate triggers the SCR and the meter should indicate low resistance. When the clip lead is removed, the meter continues to indicate low resistance if the power source is sufficient to produce the required holding current. To conduct, the SCR must have its anode more positive than its cathode. When the gate voltage is made more positive than its cathode, the SCR turns on or fires and current flows from cathode to anode. When the gate voltage is again made equal to or more negative than the cathode, current continues to flow through the SCR. The SCR is turned off or reset by reducing the current through it below its holding current....