Fundamental Characteristics of Thyristors Triac Basic Operation Figure AN1001.4 shows the simple block construction of a Triac. When reversal of output is required, the firing pulses for the conducting bridge are stopped and the second bridge is gated. (Marked NORMAL). Diodes ‘D1’ to ‘D4’ rectify ac to dc. 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. The value of emf of a cell does not remain constant but varies with the change in specific gravity of electrolyte, temperature and the […] Based on the experiment, there are four possible ways to trigger the TRIAC. 5. Voltage: Average emf of cell is approximately 2.0 volts. For a TRIAC this tr… What are the advantages of six pulse converter? Observe the ammeter reading by reducing the anode-cathode supply voltage V, 9. The first quadrant is the region wherein MT2 is positive with respect to MT1 and vice-versa for the third quadrant. If thyristor does not turn off even after pot is at the highest resistance value, then reduce anode supply voltage. Note that there are separate switches are provided for electronic circuit ON/OFF and control circuit ON/OFF. Demonstrate bi-directional conduction of a gated TRIAC. The electric supply system can be classified into i) d.c. or a.c. system (ii) overhead, Experiment no. 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. 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. 4. The DC motors are undisputable electrical equipments in any application. The system is provided with 2 no AC switches, one for electronic control circuit. 1 Object Load test on DC Shunt motor. What is the maximum value of firing angle which can be obtained from the circuit? The test point TP5 & TP6 display the ZCD waveform of the system. The force acting tangentially on the pulley is equal to the difference between two spring balance readings. What is the output ripple voltage frequency of three phase half wave converters? f) Connect the oscilloscope across DS1 to monitor the load voltage. c) Momentarily ground the oscilloscope vertical input and position the trace at the center of the CRT for a zero volt reference. The pulley is fitted on the shaft of a motor. 2. The term TRIAC is a genericised trademark. Plot the graph of VORMS v/s 〈. 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. To conduct the performance of single phase fully controlled bridge converter. Fig. Select proper desired mode of operation under closed loop/ open loop system. Before you switch on the power, connect motor cable (12 pin johson cable) and proximity switch cable (3 pin socket) correctly. The system to demonstrate the functioning of this 1 phase dual converter is housed in a sturdy MS powder coated box. the power station, the transmission lines, and the distribution system. : keep motor running at about 100 v with negligible load on the motor. Its three terminals are MT1 (main terminal 1), MT2 (main terminal 2) and G (gate). Triac means the device for AC control composed of 3 electrodes. Now turn OFF power circuit & connect the motor to the output socket with no load on the motor. Take down the readings in tabular form and analyze. 5. Study the waveforms for various firing angle by varying the pot in R trigger circuit. Yes. To study about single phase dual converter, 2. Current ‘I’, charges capacitor ‘c’ at a rate determined by ‘R’ voltage across capacitor is marked by ‘Vc’ as shown. A synchronized UJT triggered circuit using an UJT is shown in the figure. 2. 1. Interconnected System Theory The conveyance of electric power from a power station to consumes’ premises is known as Electric supply system. But here the controlling parameter is gate –emitter voltage VGE because IGBT is a voltage –controlled device. What is commutation angle of a rectifier? … IGBT is constructed virtually in the same manner as a power MOSFET. ☞Set both voltages to minimum position, and then switch on SPDT. To understand performance of SCR/TRIAC/DIAC/MOSFETS and IGBT. Name the three regions of operation in an IGBT. d) Look at your circuit and then record in Table 8-1 the triggering mode of Q1 in this configuration. With motor load connected, the switch SW3 if then in upward position, connects the armature circuit to lamp load (ensuring that thyristor o/p is disconnected), the stored KE in motor rotor is converted into DC voltage which lights the lamp momentarily & dissipates all the stored energy in the motor rotor in the lamp load & motor comes to halt immediately, indicating the process of dynamic braking. The various types of three-phase phase-controlled converters are 3 phase half-wave converter, 3-phase semi converter, 3-phase full controlled and 3-phase dual converter. There is however; a major difference in the substrate. j) Reduce the power supply voltage to zero. V. K. Thombare. 2. Measure the dc plus peak waveform across CR1. 6. 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. Due to insulated gate, negligible gate current flows. Compare Power MOSFET’s , IGBT with BJT’s. Any type of motor Shunt, Series or Compound can be tested. Observe that capacitor voltage is set at every half cycle. 6-12(a) and attaching 2 main electrodes and 1 gate electrode. 6. Explain the working operation of V-I characteristics of S.C.R. To study UJT trigger circuit for half wave and full wave control. When the dimmer voltage is around 32 volts the DIAC starts conducting as indicated by M3 meter. Triac is the word derived by combining the capital letters from the words TRIode and AC. 2mm Patch cords. Why? Calculate the dc output voltage using the equation. 209--Power system lab Manual by Prof.Mrs. They are able to switch high voltages and high levels of current, and over both parts of an AC waveform. 4. For motor load 12 pin socket is provided with 110 v DC motor. Single line Diagram of power system 2. A three-phase fully-controlled bridge rectifier can be constructed using six SCRs. What is Dc output voltage of single phase full wave controller? ☞Increase VAK voltage to maximum position. The output voltage V0 across the load terminals is controlled by varying the firing angles of SCRs T1, T2, T3. 4. Eventually a forward current is established as shown in fig. Efficiency. Load the motor & observe the effect on the o/p waveform across attenuated output test points. Define Holding current, Latching current on state resistance, Break down voltage, 3. If JFETs are operated with reverse bias on their gate leads to prevent gate current. IGBT characteristics is a power electronics experiment board to study and understand the vi characteristics of IGBT provided with in built power supply : firstname.lastname@example.org : (+91) 9755591500 Initially connect for delta operation.. Keep load control pot in minimum position. Ring main system 5. During the positive half cycle, SCRs T1 and T2 are forward biased. Results are accurate. NV6532 TRIAC Characteristic Trainer 2. You may observe o/p waveform across the attenuated test point for o/p. Junction’s j1, j3 are forward biased and the junction j2 is reverse biased. The MOSFETs may also be operated in the enhancement mode. 1. 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. The V-I characteristics of a TRIAC is based on the terminal MT1 as the reference point. The necessary isolated DC supplies for opto isolators (8 no) are generated & an AC sensing circuit at inside is provided to achieve proper synchronization. Then a triac has four possible triggering modes of operation as follows. Yes. 1.2 To measure the gate trigger voltage and the holding current of a typical SCR by using dc measurement methods. What are the two modes of operation present in the three phase half controlled rectifiers? It can be triggered by reaching its breakover voltage (+ or -). Connect the three phase 440 volt supply to the rear of the instrument using the terminals marked R,Y,B .Connect Load bank. Note MT1, MT2 & gate terminals properly. C. Demonstrate bi-directional operation of DIAC. Diode D allows the flow of current during positive half cycle only. 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 FETs offer advantages in switching service since they do not suffer the delays associated with minority carrier storage. A gate current of specified amplitude of either polarity will trigger the TRIAC into conduction in either quadrant, assuming that the device is in a blocking condition initially before the gate signal is applied. 2. Other details remain the same as for delta connection calculations. The device can be turned OFF only by bringing the device current below a value known as holding current. Those FETs that use this technique are known as metallic oxide semiconductor field effect transistor or MOSFETs. In operation triac is equivalent to two SCRs connected in anti-parallel. 6 - UJT-SCR Time Delay Circuit, ECE121 Experiment No. Apparatus Required : 1. 5. ECE121 Experiment No. All the eight thyristors (TYN 612) are grouped into two sections are for +ve o/p & for –ve output (4 no of each group). DS1 should light. g) Is the polarity of the sawtooth inverted? (LC Commutation Circuit) Oscillation Chopper Circuit 29 8. d) Reduce the power supply voltage to zero. The switch SW3 is required to be kept in downward position for normal-dual converter operation. h) Measure the peak waveform as in step (c) above. 1. 1. What are the advantages of three phase rectifier over a single phase rectifier? annaisabel.blogspot.com, ECE121 Experiment No. To study V-I characteristics of SCR and measure latching and holding currents. Positive or negative potential across the terminals can be triggered by reaching +/- breakover voltage. TRIAC is only used in AC circuits. Observe the various waveforms on CRO by appropriately connecting test points. e) Record the characteristics of this Q1 triggering mode in Table 8-1. f) Open S2 and reduce all voltage sources to zero. IGBT is also known as metal –oxide insulated gate transistor (MOSIGT), conductively –modulated field effect transistor (COMFET) or gain –modulated FET (GEMFET). Compare UJT triggering circuit with RC firing circuit? Triac is a bidirectional thyristor with three terminals. 4. DIAC can be tested by applying about 32 volts across its terminals with both the polarities, including the limiting resistance of 2K in series with M3 meter. Zener diode ‘Z’ functions to clip the rectified voltage to a standard level, ‘Vz’ which remains constant except near the Vdc zero. You may reverse the terminals supply voltage & observe that DIAC still turns ON. 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. This makes triac circuits ideal for use in a variety of applications where power switching is needed. Turn ON the switch SW1 for electronic control circuit. The symbol and pin out of TRIAC is shown below. ... like a triac without gate terminal, as shown in figure. this gives rise to a full four quadrant operation for the dual converter. It exhibits negative resistance characteristics. 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. Demonstrate the four triggering modes of a TRIAC. Switch on the power supply to the CRO . What are the effects of load inductance on the performance of AC voltage controllers? 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. Connections are mode as shown in the circuit diagram. Verify Edc as shown from the panel voltmeter for this setting. 3. As a result of their performance, trials tend to be used for low to medium power applicati… TRIAC switch The TRIAC (Triode AC) model is designed using two anti-parallel SCR switch models as shown below. The initial set gate current should be taken as the value, for gate current for the consecutive readings. VL = 81 volts (RMS), (i.e. 3. R2 is the variable resistance. However a large input signal may momentarily overcome the reverse bias and turn on gate diodes drawing appreciable current from the source. 7. APPARATUS REQUIRED: Trainer kit, Patch cards, Multimeters. Experiment Steps ☞Connections are made as shown in the circuit diagram. When ac voltage is supplied across the terminals of the bilateral gated TRIAC, it is shorted, wherein a complete sine-wave input is supplied across the load to the TRIAC. 1 EXPERIMENT TITLE MODULE NO. Does DS1 light? The forward voltage drop across the device in the ON state is around one volt. Explain how synchronization of the triggering circuit with the supply voltage across SCR is achieved? Yes. Experiment No Page. Observe the current when the device turns OFF. What are the different types of Power IGBT? Conclusion: 1. This switch should be normally in downward position. It is composed by joining p type and n type semiconductors in 5 layers as in fig. 11. 1. To obtain V-I characteristics and to find on-state forward resistance of given SCR. e) Reverse the polarity of the power supply connected to your circuit. The firing angle can be controlled up to above 150o. Be sure S2 is open initially. UJT Triggering of SCR – HWR & FWR 33 9. TP2(red) and Green( - ve of CRO):- Attenuated output for CRO. 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. For reverse characteristics, change the connection to make M. 2. Connect a & k terminal of UJT triggering circuit to the gate cathode terminals of SCR. B. characteristics by using two transistors analogy. Aim : To study the V-I characteristics of TRIAC. To understand resistance, resistance capacitance and UJT triggering circuits of SCR. 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. It is an open loop system based on a dual converter using non circulating current mode of operation. Does S1 light? Vm = Peak phase voltage, Volts , α = Firing angle, degrees, TP1 (red) and Ground (Black) :- UJT Relaxation oscillator output. Fig shows single phase fully controlled rectifier with resistive load. A.C. Distribution Radial System 4. Fig :-modes of operation of TRIAC To plot the output waveforms of single phase fully controlled bridge converter, 1- Ф fully controlled bridge converter(kit). b) Adjust the main terminal and the gate voltage sources to +6Vdc. If firing angle is greater than 90 degrees, the inverter circuit formed is called as? 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. 2. where can i get a copy of the picture of the figures? Objective B. 5. During the positive half cycle of the input voltage, SCR become forward biased but it will not conduct until its gate current exceeds Igmin . The TRIAC is a three-terminal device which can conduct in either direction. It is direct method of testing. When reversal of output is required, the firing pulses for the conducting bridge are stopped and the second bridge is triggered. As the pot P1 is moved clockwise or anticlockwise, the phase angle for reference pulse & triggering pulse goes on varying. 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. Here, both the output voltage and output current are positive. 1.3 To demonstrate the dc power control of SCR by using … This n-channel short-circuits the n- region with n+ emitter regions. Its equivalent circuit is a pair of inverted four layer diodes. You can observe various test points as described. Verify the output voltage on the basis of output voltage indication. 3. Explain the working operation of S.C.R. 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