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EXPERIMENT # 3
Objective :
To Adjust the firing angle of triac.
Theory:
A triac or tiode for alternating current is an electronic component approximately
equivalent to two silicon controlled rectifiers(SCRs/thyristors) joind in inverse paraallel
(paralleled but the polarity is reversed) and with thier gates connected together. The formal nam
for a triac is bidirectional triode thyristor.
This result in a bidirectional electronic switch which can conduct current in either
directoion when it is triggered (turrned on) and thus doesn’t have any polarity. It can be triggered
by either a positive or negative voltage being aplied to its gate electrode (with respect to A1,
otherwise known as MT1).
ONCE TRIGRRED THE DEVICE CONTINUES TO CONDUCT UNTIL THE
CURRENT THROUGH IT DROPS BELOW A CERTAIN THRASHOLD. value, the holding
current, such that as at the end of a half cycle of alternating current mains power. this makes the
triac a very convineint switch for ac circuits, allowing the control of very large power flows with
miliampere- scale control currents.in addition, applying a trigger pulse at a controllable point in
an ac cycle allows one to contrl the percentage of current that flows through the triac to the load.
APPLICATION:
Low power tirac are used in many applications such as light dimmers, speed controls for
electric fans and other electric motrors and in the modren comuterized control circuit of many
hosehold small and major appliances
however, when used with inductive loads such as electric fans , care must be taken to
assure that triac will turn off correctly at the end of each halfcycles of the ac power . for higher-
powered, more demandind loads, twoscrs in reverse parallel may b used insteadof one triac.
because each scr will have an entire half- cycle of reverse polarity voltage applied to it. however,
due to the sparate gaets , proper triggering of the scr s is more complex then triggering a triac.
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SYMBOL:
APPARATUS:
TRIAC
CAPACITORS
REISITORS
TRANSFORMER
BREADBORD
CONNECTING WIRES
PROCEDURE:
Draw the circuit diagram and make connections according to circuit diagram.now check
connections , then connect oscilloscope with rl to observe o/p voltage waveform and firing angle.
now “on” power supply and take 12 rms from transformer. use rc driver network to apply gate
signal.measure firing angle of o/p waveform. now setup r2 at differet values and take radings of
differnt firing angle.
OBSERVATION AND CALCULATION:
S.NO
R2
FIRING ANGLE
Ф1
Ф2
1
2
3
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DIAGRAM:
WAVE FORM:

Unformatted Attachment Preview

EXPERIMENT # 3 Objective : To Adjust the firing angle of triac. Theory: A triac or tiode for alternating current is an electronic component approximately equivalent to two silicon controlled rectifiers(SCRs/thyristors) joind in inverse paraallel (paralleled but the polarity is reversed) and with thier gates connected together. The formal nam for a triac is bidirectional triode thyristor. This result in a bidirectional electronic switch which can conduct current in either directoion when it is triggered (turrned on) and thus doesn’t have any polarity. It can be triggered by either a positive or negative voltage being aplied to its gate electrode (with respect to A1, otherwise known as MT1). ONCE TRIGRRED THE DEVICE CONTINUES TO CONDUCT UNTIL THE CURRENT THROUGH IT DROPS BELOW A CERTAIN THRASHOLD. value, the holding current, such that as at the end of a half –cycle of alternating current mains power. this makes the triac a very convineint switch for ac circuits, allowing the control of very large power flows with miliampere- scale control currents.in addition, applying a trigger pulse at a controllable point in an ac cycle allows one to contrl the percentage of current that flows through the triac to the load. APPLICATION: Low power tirac are used in many applications such as light dimmers, speed controls for electric fans and other electric motrors and in the modren comuterized control circuit of many hosehold small and major appliances however, when used with inductive loads such as electric fans , care must be taken to assure that triac will turn off correctly at the end of each halfcycles of the ac power . for higherpowered, more demandind loads, twoscrs in reverse parallel may b used insteadof one triac. because each scr will have an entire half- cycle of reverse polarity voltage applied to it. however, due to the sparate gaets , proper triggering of the scr s is more complex then triggering a triac. SYMBOL: APPARATUS: • • • • • • TRIAC CAPACITORS REISITORS TRANSFORMER BREADBORD CONNECTING WIRES PROCEDURE: Draw the circuit diagram and make connections according to circuit diagram.now check connections , then connect oscilloscope with rl to observe o/p voltage waveform and firing angle. now “on” power supply and take 12 rms from transformer. use rc driver network to apply gate signal.measure firing angle of o/p waveform. now setup r2 at differet values and take radings of differnt firing angle. OBSERVATION AND CALCULATION: FIRING ANGLE S.NO 1 2 3 R2 Ф1 Ф2 DIAGRAM: WAVE FORM: Name: Description: ...
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