This allows the component to conduct in both directions. Other details remain the same as for delta connection calculations. As soon as the capacitor discharges, it starts to recharge as shown. A website for Electronics and Communications Engineering students. It is composed by joining p type and n type semiconductors in 5 layers as in fig. Then switch on the power for electronic and control circuit. 3. Verify Edc as shown from the panel voltmeter for this setting. What is a three phase controlled rectifier? For a TRIAC this tr… For any one particular firing angle plot the waveforms of the ac voltage, voltage across the load and the SCR. Explain the different working modes of operations of a TRIAC? Pulse at the two secondary windings feeds the same in phase pulse to two SCRs of a full wave circuits. To study Three Phase Converter (Half Wave and Full wave Bridge). 10.Conduct an experiment to produce variable DC o/p voltage (chopper), plot o/p voltage v/s duty cycle for Variable frequency & Fixed Frequency. SCR Characteristics 3 2. EXPERIMENT-1(a) V-I CHARACTERISTICS OF SCR AIM: 1. Voltage: Average emf of cell is approximately 2.0 volts. For large power dc loads, 3-phase ac to dc converters are commonly used. 6.3.2 illustrates the main characteristics of the triac. Make the connections as per the circuit diagram. When reversal of output is required, the firing pulses for the conducting bridge are stopped and the second bridge is gated. The device can be turned OFF only by bringing the device current below a value known as holding current. 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 direction, whereas the TRIAC conducts in both the directions. V-I characteristics of TRIAC are obtained. Hence SCRs T1 and T3 turned off. A fully controlled converter or full converter uses thyristors only and there is a wider control over the level of dc output voltage. Before you switch on the power, connect motor cable (12 pin johson cable) and proximity switch cable (3 pin socket) correctly. TRIAC Characteristics 9 3. Connect CRO and observe all waveforms for TP1, TP2, TP3 & TP4 for both +ve & -ve outputs, by rotating pot P1 in clockwise and anticlockwise direction respectively. Any type of motor Shunt, Series or Compound can be tested. 4. IGBT Characteristics 17 5. Turn ON the switch SW1 for electronic control circuit. It is an open loop system based on a dual converter using non circulating current mode of operation. 1. Now gradually load the motor and take ,speed, current voltage readings. Nvis 6530A Understanding Characteristics of DIAC, TRIAC & SCR is remarkable and frequently used laboratory equipment which is designed to explain fundamentals and working of DIAC, TRIAC & SCR. If you observe the waveform at TP5 & TP6 you can see phase shifted triggering pulses for thyristor. Apparatus Required : 1. As the firing angle is retarded beyond this point, so the load current starts to freewheel through the diode for certain periods, thus cutting off the input line   current, and preventing the output terminal load voltage from swinging into the negative direction. 3. characteristics by using two transistors analogy. i.e. Observe the ammeter reading by reducing the anode-cathode supply voltage V, 9. What are the advantages of three phase controlled rectifiers? iv List of Experiments Exp No Experiment Nmae Page No 1 Static characteristics of SCR and DIAC. 1 Object Load test on DC Shunt motor. In the former, only one of the bridges is triggered. During negative half cycle (π to 2π). The circuit symbol and schematic construction of one such device are shown in fig.1. Select proper desired mode of operation under closed loop/ open loop system. 3 - SCR AC Power Control, ECE121 Experiment No. Ι + Mode = MT2 current positive (+… 4. 6-12(a) and attaching 2 main electrodes and 1 gate electrode. For firing angle less than 30°, the output terminal voltage of the converter is always positive, and the freewheeling diode does not come into operation. You may connect 1HP D.C. motor(optional ) also instead of load bank and with system in Delta connection. The voltage Vz is applied to the charging circuit RC. Labels: diac, ece121 industrial electronics, experiment, triac, where can i get a copy of the picture of the figures? The term TRIAC stands for TRIode for Alternating Current. 2mm Patch cords. Field effect transistors, on the other hand do not normal require any input current and are unipolar devices. visit my other blog: Then a triac has four possible triggering modes of operation as follows. When ‘Vc’ reaches the unijunction threshold voltage Vz, the t-B1 junction of UJT breaks down and the capacitor ‘c’ discharges through the primary of pulse transformer sending a current ‘C2’ as shown. An electron movement in the n-channel, in turn causes substantial hole injection from p+ substrate layer into epitaxial n- layer. Trigger pulses TP1, TP2, TP3 & TP4 for all the four thyristors in each group are generated & can be observed on test points marked properly for the +ve & -ve channels. What are the different families of thyristor devices? Connections are mode as shown in the circuit diagram. Depletion mode operated devices are normally in ON condition. Blocking voltage (VDRM)—the maximum voltage that the triac can block in either direction when the gate current is... 2. LIST OF EXPERIMENTS 1. (LC Commutation Circuit) Oscillation Chopper Circuit 29 8. This method of controlling the output power by varying the charging resistor ‘r’ is called ramp control, open loop control (or) manual control. To determine holding, latching current and break over voltage of given SCR. Fig.2 shows the characteristics of TRIAC. The n+ layer substrate at the drain in power MOSFET is now substituted in the IGBT by a p+ layer substrate called collector. What is the condition for load current should be discontinuous? 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. These disadvantages are overcome by insulating the gate terminals from the channel with a thin layer of silicon dioxide (Metallic oxide). Power MOSFET is a voltage controlled device? A TRIAC is a bidirectional thyristor (it can conduct in both directions) with three terminals. Generally power enhancement MOSFETs are used in power electronics circuits. Sufficient dead band for the generation of pulses for either +ve o/p (clockwise movement of P1) or –ve o/p (anticlockwise movement) of pot P1. 5. 4 - Unijunction Transistor, ECE121 Experiment No. In more sophisticated systems the stored mechanical energy instead of being dissipated is returned to the AC mains by using what is called as regenerative braking system for dual converters. Observe the various waveforms on CRO by appropriately connecting test points. At ωt = α, SCRs T1 and T3 are triggered, then the current flows through the L – T1- R load – T3 – N. At ωt = π, supply voltage falls to zero and the current also goes to zero. You can either connect the motor load or lamp load. Why i-mode is more sensitive among all modes? Experiment # Particulars Page # 1 Static characteristics of SCR or DIAC. For motor to start running you have to take pot P1  to most anticlockwise position. What are the effects of load inductance on the performance of AC voltage controllers? Adjust gate voltage to a slightly higher value than what is found in (a) set, Increase the anode current from latching current level with pot or by increasing the supply voltage slightly. Remove the gate supply permanently. With RL- load it becomes a two-quadrant converter. Verify the output voltage on the basis of output voltage indication. In the forward direction, the shape of the output characteristics is similar to that of BJT. 1. Rotate the pot P1 to zero position & turn it in clockwise direction the motor starts rotating in clockwise direction. It is used extensively for the control of power in ac circuit as it can conduct in both the direction. e) Record in Table 8-1 the data for this triggering mode of Q1. 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. If JFETs are operated with reverse bias on their gate leads to prevent gate current. The advantages of three phase converters over single-phase converters are as under: In 3-phase. Keep the multiplication factor of CRO’s probe at maximum position. During the positive half cycle, SCRs T1 and T2 are forward biased. As the current ‘i2’ is in the form of pulse, windings of the pulse transformer have pulse voltages at their secondary terminals. d) Look at your circuit and then record in Table 8-1 the triggering mode of Q1 in this configuration. This is the break over voltage of CR1. Initially connect for delta operation.. Keep load control pot in minimum position. 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 direction, whereas the TRIAC conducts in both the directions. 3. Since the conducting. where can i get a copy of the picture of the figures? In this system when the motor is required to be braked, the pulses for the bridge working as converter are blocked and the other bridge is operated in inverter mode. TP2(red) and Green( - ve of CRO):- Attenuated output for CRO. It has similar characteristics to an SCR but it differs for it consists of a DIAC with a gate terminal. Disclaimer: Not all information posted in this site are accurate. Objectives To study the direct loading test of DC Shunt motor by Rope-Pulley arrangement method. The FETs offer advantages in switching service since they do not suffer the delays associated with minority carrier storage. ☞Increase VAK voltage to maximum position. If firing angle is greater than 90 degrees, the inverter circuit formed is called as? Observe the current when the device turns OFF. Start the P1 from zero , you may need to adjust “P2’ slightly .Slowly increase the speed. 6. As a result of their performance, trials tend to be used for low to medium power applicati… By varying the anode- cathode supply voltage V. 6. 1. Well-known among them was Ward Leonard system. It exhibits negative resistance characteristics. 2. b) Reverse the polarity of the gate voltage supply by reversing the power supply leads connected to your circuit. Now start decreasing the anode current gradually by adjusting pot (P2). What is Dc output voltage of single phase full wave controller? g) Look at the recorded data of Table 8-1. 3. a) Reduce the gate voltage supply to zero. 5. Theory             This is direct method of testing the motor in which the motor is loaded gradually from no load to full load. Here, output voltage is either positive or negative but output current is always positive. Now turn OFF power circuit & connect the motor to the output socket with no load on the motor. 4. R.M.Shaikh/Prof.A.S... Analog Electronics Lab Manual Experiment No 1-5, Analog Electronics Lab Manual Experiment No 6-11, Analog Electronics Syllabus Wise e-Resources links. NV6532 TRIAC Characteristic Trainer 2. Once SCR starts conducting, it behaves like a conducting diode and gate has no control over the device. 2) You have to follow general test procedure as per, It indicate the variation of drain current I, This characteristic shows the variation of drain current I, Output characteristics of an IGBT show the plot of collector current IC versus Collector-Emitter voltage V, The transfer characteristics of an IGBT is a plot of collector current I. The forward voltage drop across the device in the ON state is around one volt. Write down the expression for average output voltage of three phase full converter. Fig shows single phase fully controlled rectifier with resistive load. 2. A dual is used only when reversible dc drives with power ratings of several MW are required. What are the effects of source impedance in the controlled rectifiers? Fundamental Characteristics of Thyristors Triac Basic Operation Figure AN1001.4 shows the simple block construction of a Triac. Line to line voltage i.e. A synchronized UJT triggered circuit using an UJT is shown in the figure. 1-6 2 Static characteristics of MOSFET & IGBT. This is expected because triac consists of two SCRs connected in parallel but opposite in direc tions. Fig. How is the output power to the triggering circuit controlled? 2. 1. 23-27 6 Parallel Inverter. 7. What are the different methods to turn ON the SCR? Demonstrate the four triggering modes of a TRIAC. Does DS1 light? By varying the variable resistance R, the firing angle can be varied from 0 —180° .In the negative half cycle the capacitance C charges through the diode D2 with lower plate positive to, the peak supply voltage Emax .This Capacitor voltage remains constant at until supply voltage attains zero value. Demonstrate the four triggering modes of a TRIAC. Vm = Peak phase voltage, Volts , α = Firing angle, degrees, TP1 (red) and Ground (Black) :- UJT Relaxation oscillator output. You can observe various test points as described. Connect the circuit as shown. Thank you. The three layers p+, n. Static V-I or output characteristics of an IGBT (N-channel type) show the plot of collector current IC versus collector emitter voltage VCE for various values of gate-emitter voltages. 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. What are the different types of Power MOSFET? What is the maximum value of firing angle which can be obtained from the circuit? Hence the effect of the freewheeling diode is to cause a reduction of ripple voltage of the output terminals and at the same time to divert the load current away from the input lines. The output voltage V0 across the load terminals is   controlled by varying the firing angles of SCRs T1, T2, T3. Note MT1, MT2 & gate terminals properly. b) Reverse the polarity of the gate voltage supply again. 1 Thyristors DC Characteristics PREPARED BY: J.B. G. Ibarra 1.0 OBJECTIVES 1.1 To become familiar with the characteristics of the (SCR) silicon controlled rectifier and its operation. V. K. Thombare. c) Close S2 and depress S1 momentarily. Objective A. It can operate and switch both half cycles of an AC waveform. g) Is the polarity of the sawtooth inverted? As the pot P1 is moved clockwise or anticlockwise, the phase angle for reference pulse & triggering pulse goes on varying. 1. Explain how synchronization of the triggering circuit with the supply voltage across SCR is achieved? h) Measure the peak waveform as in step (c) above. please let me know where and how. You may reverse the terminals supply voltage & observe that DIAC still turns ON. 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