BEE Lab Manual

EXPERIMENT NO: 1(A)

Aim of the experiment:

To control the speed of a D.C. shunt motor by flux or field control method.

Apparatus required:

Sl.no.

Name of the Item Type Range Quantity

1. D.C. Shunt motor D.C. 220V,19A,1500RPM,5HP 12. 3 Point starter D.C. 220V,19A,5HP 13. Ammeter M.C. 1A 14. Voltmeter M.C. 300V 15. Rheostat or field

regulatorWire-wound 200Ω,2A 1

6. Tachometer digital 99999RPM 17. Connecting wires S.W.G. 8 S.W.G. As per req.8. Line tester - 500V 1

THEORY:

Field flux control method is based on the fact that by varying the flux φ, the motor speed can be changed and hence the name flux control method. A variable resistance known as shunt field rheostat is connected in series with the shunt field winding to vary the field resistance and hence the shunt field current.

Vikash College of Engineering for Women, Bargarh 1

The back emf a D.C. motor is given by

Eb=фPZN60 A

=>N =60Eb A

фPZ

=>N = K*Eb

ф , where K =

60 APZ is constant.

=>N αEb

ф

=>N αEb

I f (ф αI f) Where I f is field current

Hence this equation clearly states that, speed of the D.C. motor can be controlled above the normal range of speed by decreasing the current in the field circuit by including an external resistance in the form of a rheostat as variable resistance.

Procedure:

(i) Connect the D.C. Motor as per the circuit diagram.(ii) Ensure that the external resistance in the field circuit is minimum.(iii) After ensuring step :( ii) switch on the D.C. supply.(iv) Keep the applied voltage to the armature constant at its rated value.

Vary the field current of the motor by varying the rheostat resistance R1 in the field circuit and record the field current and the corresponding speeds of the motor.

(v) Repeat step: (iv) for various values of field current , till the speed of the motor is about 1.4 times the rated speed of the motor.

(vi) Switch off the motor supply to stop the motor.(vii) Plot the graph of the field current ( I f) verses change in speed of motor

(N).



Tabulation:

Sl.no.

Field current(If) in AMP

Speed(N)RPM

Armature voltage(v) in VOLT

1.2.3.4.5.6.7.8.9.

Advantage:

(i) As very little power is wasted in the shunt field rheostat due to relatively small value of Ish, hence it is inexpensive.

(ii) The speed control exercised by this method is independent of the machine.

Disadvantage:

(i) Only speeds higher than the normal speed can be obtained since the total field circuit resistance cannot be reduced below Rsh – the shunt field winding resistance.

(ii) There is a limit to maximum speed obtainable by this method.


Precaution:

(i) Right terminal should be properly connected according to circuit diagram.

(ii) Fuse wire of proper current capacity to be used.(iii) Do not increase the speed of the motor beyond 1.4 times the rated

speed otherwise mechanical stresses will be high, may damage the motor.

(iv) Field current should not be decreased to a very low value.

Conclusion:

From the above experiment it was found that the shunt motor changes its

speed by varying the field flux. So satisfying the working formula N α1ф .


EXPERIMENT NO: 1(B)


To control the speed of D.C. Shunt motor by armature resistance control method.

Apparatus required:

Sl.no.

Name of the items Type Range Quantity

1. D.C. Shunt motor D.C. 220V,19A,1500RPM,5HP 12. 3 point starter D.C. 220V,19A,5HP 13. Ammeter M.C., 1A 14. Voltmeter M.C. 300V 15. Rheostat or field regulator - 60Ω,5A 16. Tachometer - 99999RPM 17. Connecting wires S.W.G. 8 S.W.G. As per req.8. Line tester - 500v 1

Theory:

In armature control method the speed is varied by varying the back emf. The voltage across the armature is varied by inserting a variable resistance in series with the armature which is known as controller resistance.

The back emf of a D.C. motor /machine is given by Eb=фPNZ60 A

=>N=60Eb A

фPZ

=>N=K*Eb

ф, where k=

60 APZ is a constant


=>N αV−I aR a

ф, where Eb=V -I aRa

=>N α ( V-I aRa ) (keeping field current constant)=>N α V-I a(Ra+R)

R is the external resistance in a motor can be controlled. Before the normalRange of speed by varying the resistance in the armature circuit included in the form of a rheostat as a variable.

Procedure:

(i) Connect the D.C. motor as per circuit diagram.(ii) Ensure that the external resistance in the resistance circuit is maximum.(iii) After ensuring step:2 switch on the D.C. Supply as a result motor will

start running at allow speed.(iv) Keeping the field current to the shunt field constant vary the voltage

applied armature by the external resistance in the armature circuit.(v) Record the applied voltage and the corresponding speed.(vi) Repeat step:4 for various values of applied voltage to the

armature till the rated voltage of the motor and record the corresponding speed.

(vii) Switch off the main supply to stop the motor.


(viii) Plot the graph of the armature voltage (V) V S speed of the motor (N).


Tabulation:

Sl.no.

Armature voltage(v) in VOLT

Speed of motor(N)in RPM

Field current(If)in AMP

1.2.3.4.5.6.7.8.9.10.

Disadvantage:

(i) A large amount of power is lost in the external resistance connected in series with the armature resistance.

(ii) This method gives speed below the normal value.(iii) For specified value of external resistance the speed reduction is not

constant. It varies with the motor load.

Conclusion:

Hence we conclude that the speed can be controlled below rated by using armature.


EXPERIMENT NO: 2


To find the open circuit characteristics of D.C. shunt generator.

Apparatus required:

Sl.no.

Name of the items type range quantity

1. D.C. Shunt motor D.C. 19A,1500RPM,220V,5HP 12. 3-Point starter D.C. 220V,19A 13. D.C. Shunt generator D.C. 3KW,1500RPM,220V 14. Ammeter M.C. 0-1A 15. Voltmeter M.C. 0-300V 16. Rheostat wire wound 200Ω,5A,500Ω,2A 27. Tachometer digital 99999RPM 18. Connecting wire S.W.G. 8 S.W.G. AS per req.

Theory:

The open circuit characteristics is a graph obtained between field current (I f) and generated emg (Eg). The emf generated in the armature winding of a D.C. generator under no load operation is given by


Eg=фPZN60 A

=>Eg= KφN (P, Z and A are constant)=>Egα φ (keeping N constant) Hence at constant given speed, no load emf, Eg is directly proportional to the

flux per pole, φ which in turn depends upon the field current (If). The characteristic curve showing the relationship between the field current ( I f ) and generated emf Eg at no load and at a constant speed is known as magnetization characteristic or open circuit characteristic.

Procedure:

1) Connect the D.C. motor and the D.C. generator as per circuit diagram.2) Adjust the rheostat in the field circuit of the motor so that the additional

resistance in this circuit is zero.3) Set the potential divider feeding to the field circuit of the generator for zero

output voltage.4) Switch on the D.C. supply to the D.C. motor and start it using the starter

move the starter arm slowly till the motor builds up the speed and finally cut out all the resistance steps of the starter. Starter arm will then be hold by the holding magnet of the starter.

5) Record the generator emf due to residual magnetism.6) Adjust the speed of the D.C. motor to rated value by varying the resistance

in the field circuit.7) Switch on the D.C. supply across the field circuit of the generator.8) Vary the field current of the generator in steps and record its value and the

corresponding generated emf of the generator. Observation should be continued up to the generated voltage 25% higher than the rated voltage of the generator.

9) Switch off the D.C. supply to stop the motor and also to disconnected the generator field.

10) Plot the graph of field current (I f ) Vs output voltage (Eg).



Tabulation:

Sl.no Field current(If) in AMP

O/P voltage of generator in volt (Eg)

Speed in RPM

1.2.3.4.5.6.7.8.9.10.

Conclusion:

We observe the open circuit characteristic from the graph plotted in between (I f) and (Eg) of the generator.


EXPERIMENT NO: 3


To start the 3-Ф induction motor by star-delta method.

Equipment and material required:

Sl.no.

Equipment Type Range Quantity

1. 3-Ф induction motor squirrel age 3-Ф,415v,5HP 12. Y-∆ Starter Automatic 3-Ф,5A,415V 13. Tachometer Digital 0-10,000rpm 14. Ammeter M.I. 0-1A 15. Voltmeter M.I. 0-600V 16. Connecting load - 1.5 squ.mm As per req.7. Neon tester - 500V 18. Combination plier - 150mm 1

Theory:

At starting 3-Ф induction motor takes 5 to 7 time of full load torque. Due to this high current the winding of motor and instruments may burn further high value of mechanical thrust may damage the supply system by large voltage accompanied with high line current and may damage the machine parts. Thus to prevent all thus problems we use diff. type starters among them star-delta starter.


Star-Delta starter can be used, provided the starter winding of the motor is designed for delta connection during its normal operation. At starting, the starter winding is connected in star so that the applied voltage to each phase of the

winding is 1

√3 of the rated voltage of the motor. Once the motor has picked up the


speed, the phase of the starter winding are connected in delta, ensuring rated voltage across each place. both the terminal of each phase of the stator winding should be accessible, so that phases can be connected in star at starting and then in delta during normal running. A fore pole double throw switch is generally used change over the connections from star to delta.

Procedure:

1. The connection of the motor with the starter should be connected with proper terminal.

2. The armature is to be connected in series with switch and voltmeter in 2-Ф.3. 3 wires from main switch with the terminal of starter R, Y and B as shown in

fig.4. Then the green i.e. the star button is passed and held 3 to 5 sec. and

released. At that direction the star connection is converted to delta, automatically as the motor attained 75% of the rated speed.

Tabulation:

Sl.no. Star reading Delta reading Speed in R.P.M.Current in AMP Voltage in VOLT Current

in AMPVoltage in VOLT

1.2.

Precaution:

1. Connection should be as per diagram2. All the connection should be proper and tight.3. The meters used should be of proper rating.


4. The phase sequence should be done carefully.

Conclusion:

Thus the 3-Ф sequential cage induction motor is started with star delta starter.

EXPERIMENT NO: 4


To study the single phase induction motor/fan motor.

Apparatus required:

Sl.no.

Name of the item Type Range Quantity

1. Multimeter Digital 200Ω,2mΩ 12. Ceiling fan A.C. 1-Ф,230v,75w 13. Neon tester - 500v 14. Screw driver - 200mm 15. Combination plier insulated 8w 16. Hammer - 2” 17. Connecting wire S.W.G. 8 S.W.G. As per req.

THEORY:

In single phase fan motor there are two type of winding, one is main winding and other is auxiliary winding. One capacitor is connected in serious with the auxiliary winding permanently Main winding is also called as running winding and it is of


thick wire. Main winding have less resistance then auxiliary winding. The main winding purpose of two winding in starter is to produce phase difference.


Procedure:

1. Measure the resistance of the winding by multimeter.2. Identify the main winding and auxiliary winding.3. Make a connection diagram of the motor and make the connection as per

the circuit diagram.4. Give the supply to motor through the armature and note the current of

motor.5. Reveres the connection of the starting winding or running winding for

changing its direction of rotation.

Precaution:

1. The connection of the conduction and motor should be checked carefully.2. All the connection should be properly tighten.

Conclusion:


Hence the single phase induction motor/fan motor is studied with running to motor.

EXPERIMENT NO: 5


Measurement of current, voltage and power in R-L-C series circuit excited by single phase A.C. supply.

Apparatus required:

Sl.no.

Name of the item type range quantity

1. Voltmeter M.I. 0-300V 22. Voltmeter M.I. 0-600V 13. Capacitor - 400V,50µf, 14. Ammeter M.I. 0-5A 15. Rheostat - 50Ω,5A 16. Chock - 240V 17. Connecting wire S.W.G. 8 S.W.G. As per req.

THEORY:


In a R-L-C series circuit, the total reactance is X =X L-XC ,

X L=inductance reacranceXC=capacitance reactanceX L=2πfL , L=inductance

XC=1

2πfC , C=capacitance

V R= voltage across the resistance RV L= voltage across the inductance LV C= voltage across the capacitance CTotal impedence,

Z=√R2+X2=√R2+(XL−XC)2

Power factor, cosф =RZ

When the inductance reactance (X L) and capacitive reactance ¿) are equal then X =X L-XC=0 hence, Z = R. In that case, the circuit is said to be in electric resonance condition.

.

Calculation of current voltage and power:

V =V R+V L-V C

V=V R at

V=√V R2+(V L−V C)

2

IZ=√ I2 R2+ I 2(X L−XC)2

Z=√R2+(X ¿¿ L−XC)2¿

R = Z cosф


Cos =ф RZ

R = V R

I

X L=V L

I

XC=XC

I


Procedure:

1. Connect the resister , inductor and capacitor in series.2. The voltmeter is connected each in parallel to all resistance (0-

300V),Inductor (0-600V) capacitor 10µf and supply 230V.3. The armature is connected in series to measure current.4. Connect the circuit to source supply.5. Take reading of the voltmeters and ammeter.6. Find X L,XC and R.7. Calculate impedance, power factor and power.

Observation table:

Sl.no. Voltage in Volt

Current in Amp

V R V C V L Z R Power factor

Power

1.


Calculation:

VR=IR

=>R =VRI

VC = I*C

=>XC=V C

I

VL = I*L

=>XL=VLI

Z=√R2+(XL−XC)2

R = Z cosφ

=>cos =φRZ

P=VI cosφ

Conclusion:

Hence from the above R-L-C series experiment the current, voltage and power is measured to be _________________watt.


EXPERIMENT NO: 6


To perform open circuit test and measurement of iron loss, no load current and no load power factor of a single phase transformer.

Apparatus required:

s.l no.

Name of the items Type Range Quantity

1. Transformer I.Q. 1 KVA 12. Ammeter M.I. 0-2A 13. wattmeter dyn 1A,150V 14. Voltmeter M.I. 0-300V 15. Single phase variac - 0-270v 16. Connecting wires SWG 8 SWG As per req.7. Line tester A.C. 500V 18. Combination plier insulator - 1


Theory:

In this test low voltage (primary) is connected to a supply of normal voltage and frequency (As per the rating of transformer) and the high voltage winding draws very low current hardly 3 to 5 percent of full load current (may be up to 100% for very small rating transformer used for laboratory purposes) under the condition as such copper losses in the primary winding will be negligible .This mainly iron losses occur in the transformer under no load or open circuit condition, which are in directed by the wattmeter connected in the circuit,

Hence total iron losses = W 0(reading of wattmeter)

From the observation of this test, the parameter R 0 and X m of the parallel branch of the equivalent circuit can also be calculated, following the steps given below power drawn, W 0=V 1*I 0 cosф0

Thus, no load power factor, cosф0=W 0

V 1*I 0

Core loss component of no load current, Iw=I 0 cosф0

Magneting component of no load current,Iw=I 0 sinф0

Equipment resistance representing the core loss R0=V 1

Iw

Magneting reactance representing the magnetic current X m=V 1

Im

Procedure:

1. Connect the circuit as per circuit diagram.2. Ensure that the setting of the variac is at low output voltage.3. Switch on the supply and adjust rated voltage across the transformer

circuit.


4. Record no load current, voltage applied and no load power, corresponding to the rated voltage of transformer winding.

Tabulation:

Sl.no

Voltage reading in volt(V 0)

Ammeter reading in amp (I 0)

Wattmeter reading in watt (W 0)

1.2.3.


Calculation:

Power factor cosφ0 =W 0

V 1 I 0

Power drawn W0 = I0*V1 cosφ0 (iron loss from wattmeter reading)No load current I0 = ______________________amp. (From ammeter reading)No load primary voltage V1= ______________________volt. (from voltmeter reading)

Thus, no load power factor, cosφ0 =W 0

V 1 I 0= ___________________.

Core loss component of no load current,Iw= I0 cosφ0 = __________________.And magnetizing component of no load currentIm= I0 sinφ0 = __________________.Equivalent resistance representing the core loss,

R =V 1

Im=_______________________.


Magnetising reactance representing the magnetizing current,

Xm∗V 1

Im= ___________________.

Conclusion:

It is observed that since the normal frequency is applied to the low voltage side normal flux will be set up in the core. Hence normal iron loss will occur so in the open circuit test normally a wattmeter reading gives only the measurement iron loss W0 = ___________________watt, no load current I0 = ____________amp,And no load power factor cosφ0 = _____________. and no load power factor cosφ0 = _____________.

EXPERIMENT NO: 7


To calculate a single phase energy meter at variable loads at unit power factor, by performing short run test and dial test.

Apparatus required:

Sl.no.


1. Ammeter M.I. 0-5A 12. Voltmeter M.I. 0-300V 13. Wattmeter - 300V,5A 14. Load box - - 1


5. Energy meter A.C. 1-Ф,230V,1Kwh 1

Machine specification:

Meter constant, K-REV, Kwh, Rating AMP, C/S

Theory:

Energy meter is integrating instrument used to measure the quantity of electric energy supplied to circuit in given time. They given no direct indirection of power i.e. as to the rate which energy is being supplied because their registration are independent of the rate at which a given quantity of energy being consumed.

1 unit=1Kwh

Power factor =active power

apparent power

Meter constant =noof revolutionenergy consumed

% age of error =retedmeter cost (K )−calculated meter cost

K *100

Procedure:

Short run test:

The potential meter circuit from voltage supply (230V AC) is energized. The no of revolution made by dies of energy meter at a various load current up to its rated current is to approximately 60 sec. with the help of watch the reading of wattmeter, ammeter and voltmeter noted.


Dial test:

The load is adjusted for a full rated current the initial reading of the dial is noted. Then final reading of meter at a regular interval of 10 min. and up to 30 min. is taken. The armature , voltmeter, wattmeter reading at regular are noted.

Short run test:

Sl.no Voltmeter reading

Ammeter reading

Wattmeter reading

No of rev.

Time in sec.

E=VIt in Kwh

No of rev./Kwh

1.2.


Dial test:

Sl.no.

Voltmeter reading

Ammeter reading

Wattmeter reading

Energy meter reading

Difference in Kwh

Coil reading in Kwh

% of error

1.2.

Simple calculation:

For short run test:


For dial test:

Conclusion:

Meter in each case were calculated the error load current was plotted. It was observed from the table that most of cases are error implying slow making meter.

EXPERIMENT NO: 8


To study about the fluorescent lamp circuit and measurement of power by wattmeter and voltmeter method.

Tools and equipment rating:

Sl.no


1. Voltmeter MI 0-300V 12. Ammeter MI 0-1A 1


3. Wattmeter - 75-600v,0.5-20A 14. Combination plier - 200mm,200*8w 15. Tester AC 500v 16. Wire cutter - 150mm 17. Multimeter - digital 1

Material specification:

Sl.no


1. Connecting load AC 1.5sq.mm 12. F.L.Tube white - 40w,250v,1200mm 13. F.L.Tube frame with holder plain - 14. Choke - 40w,250v 15. Tube light starter - 40w,250v 16. connector 2way - 1

THEORY:

Fluorescent lamp:

It consists of a long glass tube internally coated with fluorescent power. The tube contains a small amount of argon together with a little mercury each electrode was attached to two small metal plates of at each end. These plates act as anode for with standing bombardment by electrons during half cycle.

Power:

In experiment power consumed=VI cos φ which given by wattmeter. Where ’V’

is voltmeter reading and φ is the angel BW current ‘I’ and voltage ‘V’.

Power factor:


Power factor=cos φ=active power

apparent power , In experiment power=VI cos φ which is

given by wattmeter, where ’v’ is voltmeter reading, ’I’ is ammeter reading and ‘φ’

is the angelBW current ‘I’ and voltage ‘V’.

Procedure:

Connect ckt as per the ckt diagram. voltage is applied through 1-Ф various till Tthe lamp glow. han this noted voltage is applied to the lamp. Than reading are taken for different value of voltage and current after the lamp started to glow.


Tabulation:

Sl.no.

Voltage(v)in volt Current(I)in amp Wattmeter reading(w)

1.

Conclusion:

From the above experiment the power and the power factor of the fluorescent lamp was found out _______________and_____________ respectively in wattmeter and voltmeter method.




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