c) Adjust the gate supply voltage to 6 Vdc. It is used extensively for the control of power in ac circuit as it can conduct in both the direction. Vary the firing angle in steps and note the readings of waveforms in CRO. Objectives To study the direct loading test of DC Shunt motor by Rope-Pulley arrangement method. Note MT1, MT2 & gate terminals properly. CIRCUIT DIAGRAM: Fig 1.1(a) Circuit diagram for VI characteristics of SCR. Since the TRIAC is a bi-directional device the current can either flow from MT1 to MT2 or from MT2 to MT1 when the gate terminal is triggered. A rope or leather belt is wound round the pulley & its two ends are attached to two spring balances F 1 & F 2 . LIST OF EXPERIMENTS 1. The main advantage of this system lies in the smallest time interval during which motor can be brought to rest. Experiment No : 2 Experiment Name : Study of V- I Characteristics of TRIAC. SCR Characteristics 3 2. Verify the output voltage on the basis of output voltage indication. Thereby facilitating conversion of DC power onto AC. You may observe o/p waveform across the attenuated test point for o/p. Triac is a bidirectional thyristor with three terminals. Write down the expression for average output voltage of three phase full converter. V-I characteristics of TRIAC are obtained. This type of full wave rectifier circuit consists of four SCRs. Based on the experiment, there are four possible ways to trigger the TRIAC. Bring pot P1 to zero position & turn ON switch SW2 for power circuit, the thyristor circuit is energized & you can observe the lamp intensity control. Resistor R1 lowers Vdc to a suitable value for the zener diode and UJT. Remove the gate supply permanently. 4. a) Reduce the main terminal supply voltage to zero. C. Demonstrate bi-directional operation of DIAC. 6 - UJT-SCR Time Delay Circuit, ECE121 Experiment No. 5. 5. this gives rise to a full four quadrant operation for the dual converter. Now gradually load the motor and take ,speed, current voltage readings. Connections are made as shown in the circuit diagram. 1. The firing angle can be controlled up to above 150o. To study the operation of three phases SCR half controlled converter, To study the basic operation principle of a 3 phase half controlled converter, To study the characteristics of converter waveforms, 3- Ф fully controlled bridge converter(kit). Switch on the power supply to the CRO . The characteristics of a TRIAC are similar to those of an SCR, both in blocking and conducting states, except for the fact that SCR conducts only in the forward … b) Reverse the polarity of the gate voltage supply again. Ensure pot P1 in zero position & SW3 is in downward (NORMAL) position. where can i get a copy of the picture of the figures? d) Reduce the power supply voltage to zero. Voltage at terminal MT 2 is positive with respect to terminal MT 1 and gate voltage... Second Quadrant Operation of Triac. 2. The bridge circuit has two halves, the positive half consisting of the SCRs T1, T3 and T5 and the negative half consisting of the SCRs T2, T4 and T6. When reversal of output is required, the firing pulses for the conducting bridge are stopped and the second bridge is triggered. It is an open loop system based on a dual converter using non circulating current mode of operation. It is composed by joining p type and n type semiconductors in 5 layers as in fig. It’s Voltage to Current (IV) Characteristics is as shown in the Fig below. In this mode the device is normally in off condition and a sufficiently large positive voltage on the gate terminal can turn on the device. For motor load 12 pin socket is provided with 110 v DC motor. It is direct method of testing. TRIAC is only used in AC circuits. For reverse characteristics, change the connection to make M. 2. Other details remain the same as for delta connection calculations. Explain the operation of single phase Dual Converter, What are the application of single phase   Dual converter, What is the difference between dual converter and Cycloconverter, 209--Power system lab Manual by Prof.Mrs. 11. Fig. Triac can be triggered by both positive and negative polarity voltages applied at the gate. Once the gate V. For a DIAC, there is a breakover voltage present in either direction. IGBT Characteristics 17 5. We now know that a “triac” is a 4-layer, PNPN in the positive direction and a NPNP in the negative direction, three-terminal bidirectional device that blocks current in its “OFF” state acting like an open-circuit switch, but unlike a conventional thyristor, the triac can conduct current in either direction when triggered by a single gate pulse. R2 is the variable resistance. 6. a) Examine the circuit shown in Fig. 1. What are the different types of Power MOSFET? Now start decreasing the anode current gradually by adjusting pot (P2). As there is complete isolation of power circuit & mains supply, no isolating transformer is required for CRO. 05-09 3 Controlled HWR and FWR using RC triggering circuit 10-14 4 UJT firing circuit for HWR and FWR circuits 15-20 5 Generation of firing signals for thyristors/ trials using digital circuits / microprocessor. 1. Measure the dc plus peak waveform across CR1. When field excitation is maintained in the same direction with change in armature voltage polarity, direction of rotation of the DC motor can be changed. Vm = Peak phase voltage, Volts , α = Firing angle, degrees, TP1 (red) and Ground (Black) :- UJT Relaxation oscillator output. A dual is used only when reversible dc drives with power ratings of several MW are required. Does DS1 light? To study single phase fully controlled bridge converter. To obtain V-I characteristics and to find on-state forward resistance of given SCR. Field effect transistors, on the other hand do not normal require any input current and are unipolar devices. You can either connect the motor load or lamp load. Its three terminals are MT1 (main terminal 1), MT2 (main terminal 2) and G (gate). The electric supply system can be classified into i) d.c. or a.c. system (ii) overhead, Experiment no. The switch SW3 on the right hand side of main power is used to demonstrate the dynamic braking of the system. It can operate and switch both half cycles of an AC waveform. To plot the output waveforms of single phase fully controlled bridge converter, 1- Ф fully controlled bridge converter(kit). 3. Capacity 3. 8-3. b) Adjust the main terminal voltage to 6.3 Vac. Labels: diac, ece121 industrial electronics, experiment, triac, where can i get a copy of the picture of the figures? Now connect for star connection .Connect lamp load bank .Do not connects motor when system is in ‘Star connection’ In this case the line voltage will be 140 volts. Observe the various waveforms on CRO by appropriately connecting test points. Diodes ‘D1’ to ‘D4’ rectify ac to dc. 2. ü Power Source 6.3 Vac, 500mA, ü Power Source 6 Vdc, 500mA, ü C1 0.1μF, electrolytic, ü DS1 Miniature lamp, ü Q1 DIAC, ST2, ü R1 47Ω, 1W, ü R2 10KΩ, 1W, ü S1 PBNO, ü S2 SPST. The following points may be noted from the triac characteristics: The V-I characteristics for triac in the Ist and IIIrd quadrants are essentially identical to those of an SCR in the Ist quadrant. Triac means the device for AC control composed of 3 electrodes. When in operation, a TRIAC is equivalent to two SCRs connected in anti-parallel. UJT Triggering of SCR 23 7. Does S1 light? Circuit Diagram : Theory: An TRIAC is a device which can be turned on through the gate pulse for both positive and negative values of V AK and turned off using power circuit i.e., turn on is controlled … In the middle (marked zero position) none of the pulses for triggering the thyristors are generated. Objective B. The advantages of three phase converters over single-phase converters are as under: In 3-phase. 16-19 4 20 AC- voltage controller by using TRIAC-DIAC combination.-22 5 UJT firing circuit for HWR & FWR. 2. As the current ‘i2’ is in the form of pulse, windings of the pulse transformer have pulse voltages at their secondary terminals. The two modes of its operation are non-circulating current mode and the circulating current mode. When the dimmer voltage is around 32 volts the DIAC starts conducting as indicated by M3 meter. Blocking voltage (VDRM)—the maximum voltage that the triac can block in either direction when the gate current is... 2. f) Connect the oscilloscope across DS1 to monitor the load voltage. Vary the firing angle step by step in the range 180° – 0°. Fig.2 shows the characteristics of TRIAC. 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