In this particular set up, we are using dynamic braking with the help of resistor (lamp load for visual effect). Switch on the power supply to the CRO . What type of commutation is used in this circuit? All the eight thyristors (TYN 612) are grouped into two sections are for +ve o/p & for –ve output (4 no of each group). The SCRs are triggered in the sequence T1, T2, T3, T4, T5, T6 and T1 and so on. Here, both the output voltage and output current are positive. B. As compared with the anti-parallel thyristor configuration which requires two heat sinks of slightly smaller size, a triac needs a single heat sink of slightly larger size. Does DS1 light? How is the output power to the triggering circuit controlled? 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. Switch ON the supply. When the other switch (SW2 marked power ON circuit) is switched on power transformer is brought into action & the system starts to work as dual converter. A dual is used only when reversible dc drives with power ratings of several MW are required. Measure the average dc voltage across the load and rms value of the ac input voltage using g' DMM, 10. Because they also demand no input current, they are easier to drive. 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. What are the advantages of six pulse converter? b) Reverse the polarity of the gate voltage supply again. 2. Why i-mode is more sensitive among all modes? A fully controlled converter or full converter uses thyristors only and there is a wider control over the level of dc output voltage. 1. In the middle (marked zero position) none of the pulses for triggering the thyristors are generated. the power station, the transmission lines, and the distribution system. What are the effects of source inductance on the output voltage of a rectifier? Keep CHOKE /NO CHOKE mode as per desired mode of operation. 3. 3 - SCR AC Power Control, ECE121 Experiment No. 8-5. e) Record the characteristics of this Q1 triggering mode in Table 8-1. f) Open S2 and reduce all voltage sources to zero. An electron movement in the n-channel, in turn causes substantial hole injection from p+ substrate layer into epitaxial n- layer. 7. A metallic gate is deposited on the thin layer of metal oxide (insulator) which is deposited on the channel opposite to the substrate. Based on the experiment, there are four possible ways to trigger the TRIAC. For a TRIAC this tr… Positive or negative potential across the terminals can be triggered by reaching +/- breakover voltage. What are the differences between SCR and TRIAC? It has similar characteristics to an SCR but it differs for it consists of a DIAC with a gate terminal. One particular use of triac circuits is in light dimmers for domestic lighting, and they are also used in many other power control situations including motor control. The MOSFETs may also be operated in the enhancement mode. The bipolar junction transistors are current controlled devices. TRIAC Characteristics 9 3. 2 - SCR Gate Characteristics. 5. 7. What are the effects of load inductance on the performance of AC voltage controllers? 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. To see the phase controlled converter output waveform, use a 230 / 12 V transformer for isolation purpose. When the dimmer voltage is around 32 volts the DIAC starts conducting as indicated by M3 meter. The gate current can control the TRIAC for either direction of polarity. If this switch (SW1) is ON, the triggering pulse only can be observed on CRO. The V-I characteristics of triac in the first and third quadrants are basically equal to those of an SCR in the first quadrant. The first quadrant is the region wherein MT2 is positive with respect to MT1 and vice-versa for the third quadrant. 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. annaisabel.blogspot.com, ECE121 Experiment No. It is composed by joining p type and n type semiconductors in 5 layers as in fig. 1. For lamp load a separate load bank is provided. It can be triggered by reaching its breakover voltage (+ or -). Triacs are widely used in AC power control applications. Labels: diac, ece121 industrial electronics, experiment, triac, where can i get a copy of the picture of the figures? 6.3.2 illustrates the main characteristics of the triac. MT 2 is positive with respect to MT X in the first quadrant and it is negative in the third quad rant. As the name indicates, a dual converter consists of two converters (single phase or three phases), both either fully controlled or half controlled connected to the same load. 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. Zener diode ‘Z’ functions to clip the rectified voltage to a standard level, ‘Vz’ which remains constant except near the Vdc zero. Experiment No Page. SCR with positive anode voltage would turn ON. 1 EXPERIMENT TITLE MODULE NO. Plot the graph of VORMS v/s 〈. With RL- load it becomes a two-quadrant converter. Like the SCR, the triac has a number of electrical ratings, the most significant being: 1. A three-phase fully-controlled bridge rectifier can be constructed using six SCRs. During the positive half cycle, SCRs T1 and T2 are forward biased. ☞Set both voltages to minimum position, and then switch on SPDT. iv List of Experiments Exp No Experiment Nmae Page No 1 Static characteristics of SCR and DIAC. Compare Power MOSFET’s , IGBT with BJT’s. A TRIAC is a bidirectional thyristor (it can conduct in both directions) with three terminals. It can operate and switch both half cycles of an AC waveform. Connections are made as per the circuit diagram. The enhancement MOSFET is used as a switch in power electronics by keeping, Switching times (turn ON and Turn Off) are very low and hence switching loss is, STUDY OF INSULATED GATE BIPOLAR TRANSMISTOR, IGBT is a new development in the area of power MOSFET technology. Connect the three phase 440 volt supply to the rear of the instrument using the terminals marked R,Y,B .Connect Load bank. For each firing angle observe the output waveform through CRO. Conduct an experiment to control the illumination of incandescent lamp using TRIAC, DIAC combination. Steps No.2, 3, 4, 5, 6, 7, 8 are repeated for another value of the gate current I, Note: - Follow the same design procedure for TRIAC connection sting, 1. e) Reverse the polarity of the power supply connected to your circuit. Junction’s j1, j3 are forward biased and the junction j2 is reverse biased. 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. Verify Edc as shown from the panel voltmeter for this setting. 1.2 To measure the gate trigger voltage and the holding current of a typical SCR by using dc measurement methods. For motor to start running you have to take pot P1 to most anticlockwise position. 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. e) Record in Table 8-1 the data for this triggering mode of Q1. d) Close S2 and depress S1 momentarily. TP2(red) and Green( - ve of CRO):- Attenuated output for CRO. To study the characteristics of single phase dual converter, 1. 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. Triac is the word derived by combining the capital letters from the words TRIode and AC. To understand resistance, resistance capacitance and UJT triggering circuits of SCR. This type of full wave rectifier circuit consists of four SCRs. To study UJT trigger circuit for half wave and full wave control. To conduct the performance of single phase fully controlled bridge converter. No 1. 5. 7. Interconnected System Theory The conveyance of electric power from a power station to consumes’ premises is known as Electric supply system. 3. Fig.2 shows the characteristics of TRIAC. 1. 8-3. b) Adjust the main terminal voltage to 6.3 Vac. Verify the output voltage on the basis of output voltage indication. For reverse characteristics, change the connection to make M. 2. Define Holding current, Latching current on state resistance, Break down voltage, 3. 1) Select Triac as the device under test by referring to the top RHS diagram. Fig shows single phase fully controlled rectifier with resistive load. The test point TP5 & TP6 display the ZCD waveform of the system. Note MT1, MT2 & gate terminals properly. It is transmitted over large distance to load centers with the help of conductors known as transmission lines. If you observe the waveform at TP5 & TP6 you can see phase shifted triggering pulses for thyristor. 8. Here, output voltage is either positive or negative but output current is always positive. Be sure S2 is open initially. Then throw the switch SW3 in upward position. Like a power MOSFET, an IGBT has also thousands of basic structure cells connected appropriately on a single chip of silicon. Only a small leakage current flows through the device. In the forward direction, the shape of the output characteristics is similar to that of BJT. Different information/references for different major subjects of this course are made available for them. To study V-I characteristics of SCR and measure latching and holding currents. : keep motor running at about 100 v with negligible load on the motor. The purpose of a dual converter is to provide a reversible DC voltage to the load, typically a separately excited DC motor. Average output voltage, Vo = (2*Vm / Π ) *cosα. Thus stored KE will be converted into electric energy & lamp will glow momentarily & motor comes halt immediately. Keep the multiplication factor of CRO’s probe at maximum position. Temperature rise of machine can be noted. The force acting tangentially on the pulley is equal to the difference between two spring balance readings. 5. The n+ layer substrate at the drain in power MOSFET is now substituted in the IGBT by a p+ layer substrate called collector. ☞Increase VAK voltage to maximum position. How can the capacitor charging be controlled? Objectives To study the direct loading test of DC Shunt motor by Rope-Pulley arrangement method. ... like a triac without gate terminal, as shown in figure. The DC motors are undisputable electrical equipments in any application. The symbol and pin out of TRIAC is shown below. In operation triac is equivalent to two SCRs connected in anti-parallel. You may have to adjust pot marked “ADJUST” to get DC output voltage between approximately 50 volts D.C. to 175 volt D.C. You may observe the waveforms at TP1, TP2 and TP4. 5. a) Reduce the gate voltage supply to zero. It is used extensively for the control of power in ac circuit as it can conduct in both the direction. 2. Vm = Peak phase voltage, Volts , α = Firing angle, degrees, TP1 (red) and Ground (Black) :- UJT Relaxation oscillator output. SCRs T3 and T4 forward biased. Yes. To understand the latching current, holding current. V-I characteristics of TRIAC are obtained. 9. When reversal of output is required, the firing pulses for the conducting bridge are stopped and the second bridge is triggered. f) Connect the oscilloscope across DS1 to monitor the load voltage. Three-phase half-wave converter is rarely used in industry because it introduces dc component in the supply current. The triac has on and off state characteristics similar to SCR but now the char acteristic is applicable to both positive and negative voltages. 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