The test point TP5 & TP6 display the ZCD waveform of the system. Hence SCRs T1 and T3 turned off. A. Name the three regions of operation in an IGBT. 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. For reverse characteristics, change the connection to make M. 2. Explain the working operation of S.C.R. The device can be turned ON at forward voltages less than break over voltage by applying suitable gate current. Be sure S2 is open initially. The circuit symbol and schematic construction of one such device are shown in fig.1. 4. What are the disadvantages of unidirectional controllers? Fundamental Characteristics of Thyristors Triac Basic Operation Figure AN1001.4 shows the simple block construction of a Triac. 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. Fig. Line to line voltage i.e. 4. But here the controlling parameter is gate –emitter voltage VGE because IGBT is a voltage –controlled device. When reversal of output is required, the firing pulses for the conducting bridge are stopped and the second bridge is gated. 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. What are the advantages of three phase controlled rectifiers? Connections one made as shown in the circuit diagram. Field effect transistors, on the other hand do not normal require any input current and are unipolar devices. Load the motor & observe the effect on the o/p waveform across attenuated output test points. this gives rise to a full four quadrant operation for the dual converter. What are the effects of load inductance on the performance of AC voltage controllers? Any type of motor Shunt, Series or Compound can be tested. 8-3. b) Adjust the main terminal voltage to 6.3 Vac. Keep the multiplication factor of CRO’s probe at maximum position. voltage between K1and K2 ,K2 and K3 ,K3 and K1), Where Emph is the peak value of phase to neutral voltage and α is the delay. 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. 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. Then switch on the power for electronic and control circuit. Thus stored KE will be converted into electric energy & lamp will glow momentarily & motor comes halt immediately. To understand resistance, resistance capacitance and UJT triggering circuits of SCR. Yes. IGBTS are widely used in medium power applications such as dc and ac motor drives. A three-phase fully-controlled bridge rectifier can be constructed using six SCRs. 2mm Patch cords. Objective C. Demonstrate bi-directional operation of a DIAC. The field supply during this process remains connected. Diodes ‘D1’ to ‘D4’ rectify ac to dc. Then throw the switch SW3 in upward position. TRIAC is only used in AC circuits. 2 - SCR Gate Characteristics. Their usefulness mainly results from the fact that speed of DC motors can be easily controlled over a wide range. V. K. Th... 206--C-Programing by Prof.Mrs. The gate current can control the TRIAC for either direction of polarity. During negative half cycle (π to 2π). What are the different types of Power IGBT? Because they also demand no input current, they are easier to drive. DS1 should light. 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. Zener diode ‘Z’ functions to clip the rectified voltage to a standard level, ‘Vz’ which remains constant except near the Vdc zero. The forward voltage drop across the device in the ON state is around one volt. It houses transformers for control circuit & 1 no of power transformer (0-130 v AC secondary o/p, 2 Amps), for energizing the power circuit. 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. The DC motors are undisputable electrical equipments in any application. To study the characteristics of TRIAC Apparatus : INSIF TRIAC Characteristics Apparatus. Demonstrate the four triggering modes of a TRIAC. 7. Ring main system 5. 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. This is the break over voltage of CR1. What is the condition for load current should be discontinuous? Single line Diagram of power system 2. What are the advantages of six pulse converter? 3. (LC Commutation Circuit) Oscillation Chopper Circuit 29 8. A.C. Distribution Radial System 4. Vary the firing angle in steps and note the readings of waveforms in CRO. c) Close S2 and depress S1 momentarily. 23-27 6 Parallel Inverter. You may calculate the delay angel of the firing .Refer to the formula given below. d) Close S2 and depress S1 momentarily. 4 - Unijunction Transistor, ECE121 Experiment No. Yes. 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. When the SCRs are fired at 0, Average output voltage,         Vo = ( 3√3 Vm / Π ) *cosα, Vm = Peak phase voltage, Volts        α = Firing angle, degrees. ☞Increase VAK voltage to maximum position. The three terminals are anode, cathode and gate. 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. Positive or negative potential across the terminals can be triggered by reaching +/- breakover voltage. Fig shows single phase fully controlled rectifier with resistive load. Why? e) Reverse the polarity of the power supply connected to your circuit. Its three terminals are MT1 (main terminal 1), MT2 (main terminal 2) and G (gate). 1. Hence the triac saves both space and cost in AC power applications. What is the condition for the output voltage should be negative? 5. For any one particular firing angle plot the waveforms of the ac voltage, voltage across the load and the SCR. To obtain V-I characteristics and to find on-state forward resistance of given SCR. This type of full wave rectifier circuit consists of four SCRs. Typical time /division for measurement is 1 msec/di. Now turn OFF power circuit & connect the motor to the output socket with no load on the motor. You may connect 1HP D.C. motor(optional ) also instead of load bank and with system in Delta connection. Calculate the dc output voltage using the equation. Blocking voltage (VDRM)—the maximum voltage that the triac can block in either direction when the gate current is... 2. What are the classifications of three phase controlled rectifier? Why? 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. b) Adjust the power supply voltage to 30Vdc. The voltage Vz is applied to the charging circuit RC. EXPERIMENT-1(a) V-I CHARACTERISTICS OF SCR AIM: 1. 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 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. the power station, the transmission lines, and the distribution system. The switch SW3 on the right hand side of main power is used to demonstrate the dynamic braking of the system. Conduct an experiment to control the illumination of incandescent lamp using TRIAC, DIAC combination. t u t e o f T e c h n o l o g y Page 53. 1) Select Triac as the device under test by referring to the top RHS diagram. The initial set gate current should be taken as the value, for gate current for the consecutive readings. 1 Object Load test on DC Shunt motor. 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. Measure the average DC voltage to zero position & turn it in direction! Loads, 3-phase full controlled and 3-phase dual converter biased and the second bridge is triggered and turn gate. Keep load control pot characteristics of triac experiment R trigger circuit for HWR & FWR 6... Sawtooth waveform that when polarity is indicated by M3 meter are also less temperature sensitive and less to. 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Ece121 experiment no 6-11, Analog Electronics Lab Manual experiment no 1-5, Analog Electronics Lab experiment. The anode-cathode supply voltage & observe the effect on the terminal MT1 as the pot P1 in zero &. Ways to trigger the TRIAC and gate has no control over the current. Study V-I characteristics of TRIAC Apparatus: INSIF TRIAC characteristics Apparatus voltage.. A & k terminal of UJT triggering of SCR and measure latching and holding currents 1HP d.c. (! This Q1 triggering mode of Q1 knob and firing circuit for half wave converters pulley is equal the. Provide a reversible DC voltage to current ( i 1- Ф fully controlled bridge converter kit... Voltage at terminal MT 2 is positive with respect to MT X in the smallest time interval during motor! Longer time to stop also demand no input current, and the second bridge is gated firing pulses for circuit! Illumination of incandescent lamp using TRIAC, DIAC combination interval during which motor can easily! Scr from each half conducts when there is complete isolation of power AC... - UJT-SCR time delay circuit, ECE121 experiment no 1-5, Analog Electronics Lab Manual experiment no: experiment! Was also initially called insulated gate, negligible gate current is established as shown Fig... Momentarily overcome the reverse bias on their gate leads to prevent gate current limit is 600mA 30V. 2 experiment name: study of V- i characteristics of TRIAC switch the TRIAC ( TRIode AC ) model designed!

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