Download EXPT.NO.3 TITLE: TO CONTROL SPEED OF D.C.SHUNT MOTOR

EXPT.NO.3
TITLE:
TO CONTROL SPEED OF D.C.SHUNT MOTOR BY ARMATURE VOLTAGE CONTROL
METHOD.
APPARATUS:



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D.C. SHUNT MOTER
D.C.AMMETER
D.C.VOLTMETER
RHEOSTAT
RHEOSTAT
-
230 VOLT ,12A ,3KW.
0 TO 5/10 Amp.
0 TO 300 V
1000, 1.5 TO 5 Amp.
3000, 1.2 Amp.
PRIOR CONCEPTS:
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
WORKING OF D.C.MOTOR AND DIFFERENT TYPES OF D.C.MOTOR.
CONNECTION OF D.C.MOTORS SUCH AS D.C.D.C.AMMETER AND D.C.VOLTMETER.
HOW TO HANDLE TACHOMETER FOR MEASUREMENT OF SPEED.
NEW CONCEPTS:
PROPSITION 1:

FOR CONTROLLING THE SPEED OF D.C.SHUNT MOTOR STUDENT SHOULD STUDY THE
EQUATION FOR SPEED ON D.C.SHUNT MOTOR AND THE PARAMETERS ON WHICH
SPEED OF D.C.SHUNT MOTOR DEPENENDS.

THE STUDENTS SHOULD KNOW DIFFERENCE TERMS IN THE EQUATION.
FOR SPEED OF D.C.SHUNT MOTOR
N=(V –Ia.Ra)/ I
WHERE , I=SPEED OF MOTOR.
V=APPLIED VOLTAGE.
Ia=ARMATURE CURRENT.
I=FIELD FLUX.
CONCEPT STRUCTURE 1 :SPEED OF D.C.SHUNT MOTOR
CAN BE CONTROOLED BY
BY VARYING FLUX PRODUCED IN
THE FIELD OF MOTOR
CHANGING THE APPLIED
VOLTAGE
NOT PRACTICABLE METHOD
BY VARYING THE `V`ACROSS
ARMATURE OF THE MOTOR
ONLY SPEEDS ABOVE NORMAL
CAN BE OBTAINED
ONLY SPEEDS BELOW NORMAL CAN
BE ORTAINED
LEARNING OBJECTIVES:INTELLECTUAL SKILLS:
TO UNDERSTAND CONNECTION OF THE OF D.C.SHUNT MOTOR WITH 3 POINT
STARTER.

TO CONTROL THE SPEED OF D.C.SHUNT MOTOR BY VARYING ARMATURE CIRCUIT
RESISTANCE.
MOTOR SKILLS:

ABILITY TO CONNECT 3 POINT STARTER TO START MOTOR.
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ABILITY TO VARY ARMATURE CIRCUIT RESISTANCE AND MEASURE VARIABLE SPEED
AND RECORD THE OBSERVATIONS.
INSTRUMENT:
SR.NO. INSTRUMENT
1.
D.C.MOTOR
2.
VOLTMETER
3.
AMMETER
NAME OF
MANUFACTURER
SERIAL NO.OF THE
INSTRUMENT
STEPWISE PROCEDURE:
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CONNECT THE MOTOR WITH ALL METERS AND RHEOSTAT AS PER THEIR POLARITIES
SHOWN IN FIG.
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KEEP BOTH THE REHEOSTAT IN THEIR INITIAL POSITIONS.
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SWITCH ON THE D.C.SUPPLY BY MAKING ICDP SWITCHES
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GRADUALLY ROTATE THE HANDLE OF 3 POINT STARTER IN CLOCKWISE DIRECTION
TO START THE MOTOR.
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ADJUST THE SPEED OF D.C.SHUNT MOTOR TO IT`S RATED SPEED BY VARYING THE
FIELD CIRCUIT RESISTANCE.
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NOTE DOWN THE INITIAL VOLTAGE ACROSSS THE ARMATURE TERMINALS AND ALSO
SPEED OF THE ROTOR.
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START VARYING ARMATURE CIRCUIT RESISTANCE AND NOTE DOWN
CORRESPONDING SPEED.
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PLOT THE GRAPH OF ARMATURE VOLTAGE ON X-AXIS AND SPEED ON Y-AXIS.
OBSERVATIONS:
TABLE FOR DIFFERENT READINGS
SR.NO.
VOLTAGE ACROSS ARMATURE
SPEED OF MOTOR IN RPM
CONCLUSION:

AS VOLTAGE ACROSS OF THE ARMATURE AS THE MOTOR DECREASES SPEED OF THE
MOTOR DECREASES.
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THUS WE CAN OBTAIN SPEEDS BELOW NORMAL SPEED THE MOTOR .THEREFORE
THIS METHOD CAN BE ALSO KNOWN AS SPEED CONTOL OF D.C.SHUNT MOTOR
BELOW NORMAL SPEED.
TABLE FOR DIFFERENT READINGS
SR.NO.
FIELD CURRENT If IN Amp.
SPEED OF MOTOR IN RPM
CONCLUSION:

AS THE FIELD CIRCUIT STARTS DECREASING MOTOR SPEED INCREASES.
THUS WE CAN OBTAIN SPEEDS ABOVE NORMAL SPEED THE MOTOR .THEREFORE THIS
METHOD CAN BE ALSO KNOWN AS SPEED CONTOL OF D.C.SHUNT MOTOR BELOW NORMAL
SPEED
QUESTIONS:
Q1.STATE ANY TWO USES OD D.C.SHUNT MOTOR?
Q2.STATE FLEMING LEFT HAND RULE?
Q3.WHAT ARE DIFFERENT WINDINGS OF D.C.SHUNT MOTORS.
Q4. HOW SPEED OF D.C.SHUNT MOTOR CHANGES WITH FLUX ?
Q5.HOW THE NORMAL SPEED OF THE MOTOR CAN BE BEFORE VARYING THE FLUX?
CIRCUIT DIAGRAM