Thyristors.ppt - Thyristor Devices Silicon Controlled Rectifiers(SCR By Dr Javed Iqbal Class BSc EE F-17 Army Public College of Management and Sciences

Thyristor Devices Thyristor Devices Silicon Controlled Rectifiers (SCR) Silicon Controlled Rectifiers (SCR) By: Dr. Javed Iqbal By: Dr. Javed Iqbal Class: BSc. EE, F-17 Class: BSc. EE, F-17 Army Public College of Management and Sciences, Rawalpindi Army Public College of Management and Sciences, Rawalpindi 1

Power Semiconductor Switches Power Diodes Power Transistors Thyristors 2 layer device 3 layer Device 4 layer Device  Thyristor devices can convert and control large amounts of power in AC or DC systems while using very low power for control.  Thyristor family includes 1- Silicon controlled switch (SCR) 2- Gate-turnoff thyristor (GTO) 3- Triac 4- Diac 5- Silicon controlled switch (SCS) 6- Mos-controlled switch (MCT) 2

INTRODUCTION  SCR is most popular of thyristor family due to its Fast switching action , small size and high voltage and current ratings.  It is commonly used in power electronic applications.  SCR has 3 terminals (gate provides control)  SCR is turned on by applying +ve gate signal when anode is +ve with repect to cathode.  SCR is turned off by interrupting anode current. 3 PNPN structure Symbol

TWO TRANSISTOR MODEL OF SCR 4  Gate requires small positive pulse for short duration to turn SCR on. Once the device is on, the gate signal serves no useful purpose and can be removed.