(Solved): Theory and Background: To obtain controlled output voltages, phase control thyristors are used inst ...

Theory and Background: To obtain controlled output voltages, phase control thyristors are used instead of diodes. A phase-control thyristor is turned-on by applying a short pulse to its gate. The Silicon Controlled Rectifier (SCR) has three terminals, called the anode 'A', cathode ' \( \mathrm{K} \) ', and the gate ' \( \mathrm{G} \) ' as shown in figure 1 below. Figure 1: BT152 Thyristor Symbol Procedure (Part A): 1- Connect the circuit shown in figure 2. Figure 2: Thyristor Turn-On Circuit with DC Supply. 2- Vary the \( 50 \mathrm{k} \Omega \) resistor \( (\mathrm{R}) \) until the lamp is "ON". 3- Turn off the DC supply and connect a sinusoidal AC supply of \( 20 \mathrm{Vrms} \) as shown in figure 3 below. Figure 3: Thyristor Turn-On Circuit with AC Supply 4- Vary R \( (=50 \mathrm{k} \Omega) \) until the lamp is "ON". Observation: 1- Disconnect the gate for both cases (step 2 \& step 4) when the supply is either DC or \( \mathrm{AC} \). Conclusion (Part A): 1- State if the lamp stays-on when the gate is disconnected for both cases and why? Procedure (Part B): 1- Adjust the supply unit to get full-rectified signal of \( 20 \mathrm{~V} \) peak value as shown in figure 4 . Figure 4: Rectified DC Supply Apparatus 2- Connect the circuit shown in figure 5. Figure 5 : A single phase half-wave controlled rectifier with resistive load. Observation: 1- Observe simultaneously as shown below the voltage across the load i.e.; lamp \( V_{\text {Load }}(t) \) and the thyristor \( \mathrm{V}_{\mathrm{SCR}}(\mathrm{t}) \). 2- Vary the \( 50 \mathrm{k} \Omega \) resistor and observe the effect on the waveforms and the brilliance of the lamp. 3- Observe simultaneously as shown below the voltage across \( 100 \Omega \) i.e., \( V_{B 1}(t) \) and the Thyristor \( \mathrm{V}_{\mathrm{SCR}}(\mathrm{t}) \). 4- Vary the \( 50 \mathrm{k} \Omega \) resistor and observe the effect on the waveforms. Conclusion (Part b): 1- What effect does variation of the \( 50 \mathrm{k} \Omega \) resistor has on \( V_{\text {Load }}(t) \) and \( V_{S C R}(t) \) ? 2- What effect does variation of the \( 50 \mathrm{k} \Omega \) resistor has on \( \mathrm{V}_{\mathrm{BI}}(\mathrm{t}) \) and \( \mathrm{V}_{\mathrm{SCR}}(\mathrm{t}) \) ? 3- Suggest some other applications for the circuit. 4- With the use of block diagrams, suggest another firing circuit that can be used. 5- Using the Pspice or the Spice Program, simulate the circuit in figure 5.