e.Then the DIAC is connected in reverse condition. f.The above process is repeated.
Tabulation: DIAC Characteristics: Graph Result:-Thus the V-I characteristics of DIAC was obtained and graph was drawn.
Experiment No:-4Aim:To study half controlled full wave bridge (semiconverter) rectifier. Apparatus:SCR converter kit, Oscilloscope,Voltmeter,Multimeter,Connecting wires. Circuit Diagram:-Theory: The circuit contains two SCRs and two diodes. When source Vinis positive, SCR T1can be triggered at a firing angle called αand then current flows out of the source through SCR T1first, then through the load and returns via diode D2. If Vin = E* Sin (wt)then SCR T1and diode D2conduct during α<wt<π. But here we have two diodes D2and D4instead of two SCRs. When the output of the bridge tends to becomes negative just after wt exceeds π, diode D4tends to get forward-biased and it starts conducting. Then diode D2is reverse-biased and it stops conducting. During π<wt< (π+ α) , the devices in conduction are SCR T1and diode D2and the output of the bridge is clamped at zero, assuming that the on-state drops across devices in conduction is zero. During (π + α)<wt<2π, the devices in conduction are SCR T3and diode D4and so on.. Procedure:- 1)Make connections as shown in circuit diagram 2)Select resistor and inductor from load bank 3)Observe input and output waveform.
Waveforms :-Conclusion:- Using phase controlled semiconverter we can convert ac voltage into variable dc voltage.We do not get output in negative half cycle due to inductive load.
Experiment No:-5Aim: -To study V-I characteristic of TRIAC. Apparatus: -Circuit board 0-300V high voltage supply, 0-30V low voltage supply, millimeter(0-10mA,0-1A),voltmeter(0-250V),connecting wires. Circuit Diagram:-
Theory:- TRIAC, from triode for alternating current, is a generalizedtrade name for an electronic component that can conduct current in either direction when it is triggered (turned on), and is formally called a bidirectional triode thyristoror bilateral triode thyristor.TRIACs are a subset of thyristors and are closely related to silicon controlled rectifiers (SCR). However, unlike SCRs, which are unidirectional devices (that is, they can conduct current only in one direction), TRIACs are bidirectional and so allow current in either direction. Another difference from SCRs is that TRIAC current can be enabled by either a positive or negative current applied to its gateelectrode, whereas SCRs can be triggered only by positive current into the gate. To create a triggering current, a positive or negative voltage has to be applied to the gate with respect to the MT1 terminal (otherwise known as A1). Once triggered, the device continues to conduct until the current drops below a certain threshold called the holding current. The directionality makes TRIACs very convenient switches for alternating-current (AC) circuits, also allowing them to control very large power flows with milliampere-scale gate currents. In addition, applying a trigger pulse at a controlled phase angle in an AC cycle allows control of the percentage of current that flows through the TRIAC to the load
You've reached the end of your free preview.
Want to read all 47 pages?
- Summer '19
- Farooq siddique
- Alternating Current, SCRs