WINSEM2019-20_EEE3004_ETH_VL2019205004293_Reference_Material_I_09-Dec-2019_3_NEWSCRnew.pdf - Thyristor Devices Silicon Controlled Rectifiers(SCR

WINSEM2019-20_EEE3004_ETH_VL2019205004293_Reference_Material_I_09-Dec-2019_3_NEWSCRnew.pdf

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Thyristor Devices Silicon Controlled Rectifiers (SCR)
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ObjectivesDraw and explain the i-v characteristics of a thyristor. Explain the operating principle of a thyristor in terms of the “two transistor analogy”. Draw and explain the switching characteristics of a thyristor.
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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 Rectifier (SCR) 2- Gate-turnoff thyristor (GTO) 3- Triac 4- Diac 5- Silicon controlled switch (SCS) 6- Mos-controlled switch (MCT)
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Introduction SCR is most popular of thyristor family due to its Semi switching action , small size and high voltage and current ratings.(300V, 25A-----6kV, 4kA) SCR has 3 terminals (gate provides control) SCR is turned on by applying +ve gate signal when anode is +ve with respect to cathode. SCR is turned off by interrupting anode current. PNPN structure Symbol
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Operation of SCR The SCR has two states : a high-current low- impedance ON state and a low-current high- impedance OFF state. The basic transistor action in a four-layer p–n–p–n structure is analysed first with only two terminals, and then the third control input is introduced.
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Ideal Characteristic Of SCR
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Physical Operation and Characteristics: The physical operation of the SCR can be explained clearly with reference to the current–voltage characteristics. Forward blocking Forward Conduction Reverse blocking
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