SPEED CONTROL OF DC MOTOR USING TRIAC

V.Narendra,III year,EEE BranchSVCN.

INTRODUCTION

DC motors are widely used in industry because of its low cost, less complex control structure and wide range of speed and torqueWith the the increasing use of power

semicondutor units, the speed control of DC motor is increasingly getting sophisticated and precise.

TRIACA triac is a bidirectional thyristor with

three terminals.

Its three terminals are designated as MT1(main terminal 1),MT2 & gate by G.

Triac can be turned on in each half cycle of the applied voltage by applying a positive or negative voltage to the gate with respect t0 terminal MT1.

To successfully trigger a triac,gate current must come from the main terminal 2(MT2) side of the circuit.

CIRCUIT SYMBOL

SPEED CONTROLThe three methods of speed control

are

Armature voltage controlled

Armature resistance controlled

Flux controlled

ARMATURE VOLTAGE CONTROLThe output delivered by the motor(speed)

decreases with decrease in applied voltage

BLOCK DIAGRAM

OUTPUT WAVEFORMS

COMPONENTSDc motor

Triac

Diac

Capacitors- C1,C2,C3,C4(1F)

Resistors- R1-180Ω,

R2-68k,

R3-47K,

ADVANTAGESIn earlier days speed of the dc motor was

controlled using resistor which resulted in power loss but introduction of triac eliminated the power loss

Armature voltage control method gives good speed regulation and high efficiency

Gives a large speed range with any desired number of speed points

DISADVANTGESToday Introduction of IGBT made the speed

control of dc motor more feasible

Commutation circuit used in the circuit makes speed control less precise

THANK YOU

ANY QUIRIES ?