ELECTRICAL MACHINERY LAB (436) - madinpoly.commadinpoly.com/pdf/labmanual/3/ELECTRICAL MACHINERY LAB...

ELECTRICAL MACHINERY

LAB (436)

DEPARTMENT OF ELECTRICAL & ELECTRONICS

ENGINEERING

TOPICS PAGE NO.

LOAD TEST ON SINGLE PHASE TRANSFORMER. 01

SC AND OC OF SINGLEPHASE TRANSFORMER. 03

LOAD TEST ON DC SERIES MOTOR 10

LOAD TEST ON DC SHUNT MOTOR. 13

OCC OF SELF EXCITED DC GENERATOR 16

SWINBERN’S TEST 19

LOAD TEST ON DC SHUNT GENERATOR 22

OCC OF SEPERATELY EXCITED DC SHUNT

GENERATOR 27

POLARITY AND TURNS RATIO TEST 30

BANKING OF TRANSFORMERS 35

ELECTRICAL MACHINERYLAB DEPARTMENT OF EEE

MA’DIN Polytechnic college 1

LOAD TEST ON SINGLE PHASE TRANSFORMER

AIM:-

To conduct a no load test on given single phase transformerand determine the regulation for different

load.and plot the curves.

CIRCUIT DIAGRAM

MACHINE DETAILS

METERIALS REQUIRED

1. Ammeter (0-15A) MI 1NO

2. Voltmeter (0-150v) MI 1NO

3. Wattmeter (300v,15A,upf) 1NO

4. Ammeter (0-5A) MI 1NO


6. Wattmeter (300v,30A,upf) 1NO

THEORY

In this test the efficiencies and regulation are detrermind by direct loading of the given single phase

transformer . this test is very often carried out in practice excepting for small sizes ,owing to the difficulty of

obtaining a suitable load and the loss of power involved.

When ever a transformer is loaded its secondary terminal voltage changes with increased load ,if the supplied

primary voltage is held constent.the change in secondary voltage from no load to full load expressed ias



percentage of no load voltage is known a voltage is known as voltage regulatin of a transformer (ie, secondary

voltage at noload –secondary voltage at full load) 𝐸2−𝑉2

𝐸2 (the secondary rated voltage of a transformer is equal to

the secondary voltage at no load,ie,E2

The efficienciy of a transformer is defaind as the ratio of output power to input power,thus efficeiency=output

power/input power

In this experiment input power is measured directly from the wattmeter connected in the primary side and

output power is obtained by multiplying the volt meter reading and ammeter reading in the secondary side.

PROCEDURE:-

1. Connect the circuit diagram as per the circuit diagram

2. Adjust the autotransformer till the voltmeter reads rated voltage.

3. Note the no load readings and enter them as first set of readings in tabular column.

4. Load the transformer gradually and take all meter readings each time till the secondary current reaches

rated value.

5. Tabulate the readings. And finish the work

TABULATION

Sl No I1 in

Amps

V1 in

volts

W in

watts

I2 in

Amps

V2 in

volts

Input

in

watts

Output=V2xI2 %efficiency %

Regulation

CALCULATION

Output=V2xI2.

Input= W

%efficiency=𝑂/𝑝

𝑖/𝑝 x100.

Regulation= 𝑜𝑉2−𝑉2

𝑜𝑉2 x100.

RESULT

.



OPEN CIRCUIT AND SHORT CIRCUIT TEST OF TRANSFORMER

AIM

To conduct open circuit and short circuit test in given transformer. Predetermine the following

1. Efficiencies at various loads and power factors

2. Regulation at various power factor and loads

CIRCUIT DIAGRAM



MACHINE DETAILS

METERIALS REQUIRED

1. Ammeter (0-2.5A) MI 1NO

2. Ammeter (0-15A)MI 1NO

3. Volt meter (0-250v) 1no


5. Wattmeter (150V,5A,LPF) 1NO

6. Wattmeter (150V,15A,UPF) 1NO

THEORY

The purpose of the OC test to determine the no load loss (core loss) at rated voltage and frequency.

Shunt branch parameters of equalent circuit r0&x0 and the no load current of the transformer on winding of the

transformer. In the open circuit test the primary load current is very small(2.6% of rated current )copper loss is

negligibly small in the primary and is nil in the secondary is opened. The equalent circuit parameters r0&xo

referred to LV side can be calculated from the test result.

The no load power loss, Pi=V0*I0*COS φ0

COSφ0=Pi/V0*I0



Magnetising component of I0 =Im=I0SIN φ0

Energy component of I0=Ie=I0COS φ0

The noload resistance R0=V0/Ie and the no load reactance X0= V0/Im

These values can be transferred to hv side as R0’=R0(V2/V1)

2 and X0

’=X0(V2/V1)

2

SC Test is to conduct for determining the full load copper loss and the equalent resistance and resistance of the

transformer as refferd to the metering side. In this test one winding usually LV side is solidly short circuited and

a low voltage (2-12% of primary voltage ) is applied to the HV side such that rated current flows through the

winding since applied voltage is very low ,iron losses are very small and may be neglected. Hence the

wattmeter shows the full load copper loss Pcu for the bwhole transformer. If VSC is the voltage required to

circulate the rated current I2(KVA X 1000/V1) Then the equavalent circuit parameters can be found as

Z02=VSC/I2 and R02=PCu

Then X02= 𝑍022 + 𝑅02 These parameters can be transferred to the LV side as

R2’=R2(V2/V1)

2 and X2

’=X2(V2/V1)

2 secondary side R02 and X02 the regulation at any PF and loading factor(x)

can be predetermind as regulation= XI2(R02 COS φ0+- X02 SIN φ0)/V2 Where (+) for lagging and(-) for leading

power factors) from the full load copper loss and iron loss the efficiency at any loading factor and pf can be pre

determind as

Efficiency= 𝑋1000𝐾𝑉𝐴𝑋 .𝑃𝐹

𝑋1000𝐾𝑉𝐴𝑋𝑃𝐹+𝑋2𝑃𝑐𝑢+𝑃𝑖

PROCEDURE

OC TEST

1. Make connection as per the circuit diagram

2. Keep the autotransformer in minimum position

3. Adjust the auto transformer upto rated voltage of the transformer

4. Take the meter readings and tabulate the readings

5. Finish the work

SC TEST

1. Make connection as per the circuit diagram

2. Keep the autotransformer in minimum position

3. Adjust the auto transformer upto rated current of the transformer

4. Take the meter readings and tabulate the readings

5. Finish the work

.



TABULATION

𝑽𝑶𝑪

𝑰𝑶𝑪

𝑾𝑶𝑪

𝑽𝑺𝑪

𝑰𝑺𝑪

𝑾𝑺𝑪

MODEL CALCULATION

OC TEST

𝑉𝑂𝐶=

𝐼𝑂𝐶=

𝑊𝑂𝐶=

𝑊𝑂𝐶==𝑉𝑂𝐶 𝐼𝑂𝐶 𝐶𝑂𝑆∅0

∅0=𝑐𝑜𝑠−1(𝑊𝑂𝐶

𝑉𝑂𝐶 𝐼𝑂𝐶)

Wattles component 𝑖𝑤 = 𝑖0𝑐𝑜𝑠∅0

Magnetizing component 𝑖µ = 𝑖0𝑠𝑖𝑛∅0

𝑅0=𝑉𝑂𝐶

𝐼𝑊

𝑋0=𝑉𝑂𝐶

𝐼µ

These values can be transferred to hv side



R0’=R0 x K

2 X0

’=X0 x K

2

SC TEST

𝑉𝑆𝐶=

𝐼𝑆𝐶=

𝑊𝑆𝐶=

Zsc=Vsc/Isc

𝑅𝑠𝑐 = 𝑉𝑠𝑐/𝐼𝑠𝑐2

Xsc= (𝑍𝑠𝑐²− 𝑅𝑠𝑐²)

Z02=Vsc/ISC

R02=PCU/ISC2

X02= 𝑍022 + 𝑅02

These values can be transferred in to LV

R01=R02/K2

X01=X02/K2



.TO DRAW EFFICIENCY CURVE FOR A GIVEN P.F

Out put at X times F.L=X(rated KVA x 1000) cos∅

Core loss Wi= W0

Copper loss Wcs= X²Wsc

Efficiency=(Output /output+losses) x100.



Sl no Load Output(Watt) Wi(watt) Wcx(watt) Input %efficiency

TO DRAW REGULATION V/S PF CURVE

% regulation at F.L for a given P.F= 𝐼𝑟𝑎𝑡𝑒𝑑 (𝑅02𝑐𝑜𝑠∅±𝑋02𝑠𝑖𝑛∅

𝑉2

Sl No cos∅ sin∅ % Regulation

TO FIND MAXIMUM EFFICIENCY

KVA Curresponding to maximum efficiency=KVArated X 𝐶𝑜𝑟𝑒 𝑙𝑜𝑠𝑠

𝐶𝑜𝑝𝑝𝑒𝑟 𝑙𝑜𝑠𝑠 then find efficiency as usual

Maximum efficiency= KVA MAX EFFICIENCY XPF

KVA MAX EFFICIENCY XPF +LOSSES

RESULT

Conducted the OC and SC test on the given single phase transformer and predetrermine the following

1. Efficiencies at various loads and power factors

2. Regulation at various loads and power factors

3. Equavalent circuit reffered to hv and lv side

4. Maximum efficiencies at unity PF=

5. Maximum efficiencies at 0.8PF=



LOAD TEST ON A DC SERIES MOTOR

AIM

To conduct a load test on DC series motor and plot the following graph.

1) Torque v/s armature current

2) Speed v/s armature current

3) Speed v/s torque

4) Efficiency v/s o/p

CIRCUIT DIAGRAM

MACHINE DETAILS

APPARATUS REQUIRED

1) Voltmeter 0-250V(MC) 1No

2) Ammeter 0-15A(MC) 1 No

3) Tachometer



THEORY

In series motor the torque is directly proportional to armature current. Speed N is proportional to Ed/∅. In a

series motor the field carries same current as the armature ie, ∅ ∝Ia. The series motor cannot be started

without load.

Toque= (S1-S2)xgr

Output= 2П𝑁𝑇

60.

Input=VI.


𝑖/𝑝 x100.

TABULATION

Sl

No

Voltage(V) Speed(RPM) Spring balance Torque=

(S1-

s2)rg

Output(W) Input(W) Efficiency(%)

S1 S2 S1~s2

CALCULATION

V= ………………..

Speed,N=………………………….

Spring balance, S1=…………………………….

S2=……………………………………………..

Torque,T= (s1~s2)rg, r=Radius of break drum

g= 9.8

Output= 2П𝑁𝑇

60.




𝑖/𝑝 x100.

PROCEDURE

1) Connections are made as per diagram.

2) Apply a small load to the motor and start the motor.

3) Note the meter readings

4) Vary the spring balance at different load.

5) Note the corresponding readings.

6) Tabulate the reading and plot the graph.

RESULT

The load test on series motor is conducted and plotted the graphs.



LOAD TEST ON A DC SHUNT MOTOR

AIM

To conduct a load test on DCshunt motor and plot the following graph.

5) Torque v/s armature current

6) Speed v/s armature current

7) Speed v/s torque

8) Efficiency v/s o/p

CIRCUIT DIAGRAM

MACHINE DETAILS

APPARATUS REQUIRED

1) Voltmeter 0-250V(MC) 1No

2) Ammeter 0-15A(MC) 1 No

3) Ammeter 0-3A (MC) 1No

4) Rheostat 500Ω,3A 1No

5) Tachometer



THEORY

A load test is direct method,and this method is used only for small motors, because in the case of large

motors it is difficult to dissipate large amount of heat generation

Toque= (S1-S2)xgr

Output= 2П𝑁𝑇

60.

Input=VI.


𝑖/𝑝 x100.

TABULATION

Sl

N

o

Voltage(V

)

Speed

(RPM

)

Ish Ia IL

=Ia

+

Ish

Spring balance Torqu

e=

(S1-

s2)rg

Outp

ut(W

)

Input(

W)

Efficie

ncy(%

) S1 S2 S1~s2

CALCULATION

V= ………………..

Speed,N=………………………….

Spring balance, S1=…………………………….

S2=……………………………………………..

Torque,T= (s1~s2)rg, r=Radius of break drum

g= 9.8m/s2

Output= 2П𝑁𝑇

60.




𝑖/𝑝 x100.

PROCEDURE

1) Connections are made as per diagram.

2) Rheostat kept in min. position

4) Start the motor using 4 point starter

5)Note the meter readings

6) Vary the spring balance at different load.

7) Note the corresponding readings.

8) Tabulate the reading and plot the graph.

RESULT

The load test on shunt motor is conducted and plotted the graphs.



OPEN CIRCUIT CHARACTERISTICS OF SELF EXCITED DC SHUNT

GENERATOR

AIM

To obtain open circuit characteristics of self excited DC shunt generator and to find its critical

resistance.

CIRCUIT DIAGRAM

MACHINE DETAILS

APPARATUS REQUIRED:

THEORY:



An electric generator is a machine, which converts mechanical energy in to electrical energy. The

energy conversion is based on the principle of the production of dynamically induced emf, whenever a

conductor cuts the magnetic flux; dynamically induced emf is produced in it according to Faraday’s laws of

electromagnetic induction. This emf causes a current to flow if the conductor circuit is closed.

Induced emf direction can be found by Flemings Right hand rule.

Self excited Generator:

Self -excited generators are those whose field magnets are energized from the

generator itself.

PROCEDURE:

1. Connections are made as per the circuit diagram.

2. After checking minimum position of motor field rheostat, maximum position of generator field rheostat,

DPST switch is closed and starting resistance is gradually removed.

3. By adjusting the field rheostat, the motor is brought to rated speed.

4. Voltmeter and ammeter readings are taken when the SPST switch is kept open.

5. After closing the SPST switch, by varying the generator field rheostat, voltmeter and ammeter readings

are taken.

6. After bringing the generator rheostat to maximum position, field rheostat of motor to minimum position,

SPST switch is opened and DPST switch is opened.

TABULATION

S.N

o.

Field

Current

If (Amps)

Armature

Voltage

Eo (Volts)



MODEL GRAPH:

RESULT

Thus open circuit characteristics of self excited DC shunt generator are obtained and its critical

resistance is determined.

Eo

If

Critical Resistance = Eo / If Ohms E o (

Vo

lts)

If (Amps)



SWINBERN’S TEST

AIM

Conduct no load test on dc shunt motor and [predetermine the efficiency of the machine under the following

working conditions.

a)machine working as a generator

b) Machine working as a motor

c) plot efficiency vs output

CIRCUIT DIAGRAM

MACHINE DETAILS

APPARATUS REQUIRED

SL NO APPARATUS

REQUIRED

SPECIFICATION QTY



THEORY

This is a no load test to determine the losses of the machine. the losses in the motors are

Iron loss or core losses, frictional losses, windage losses, arm copper losses

Work as generator

Efficiency= 𝑜𝑢𝑡𝑝𝑢𝑡

𝑜𝑢𝑡𝑝𝑢𝑡 −𝑙𝑜𝑠𝑠𝑒𝑠

Work as motor

Efficiency = 𝑖𝑛𝑝𝑢𝑡 −𝑙𝑜𝑠𝑒𝑠

𝑖𝑛𝑝𝑢𝑡

PROCEDURE

1. Connection are as shown in connection diagram.

2. Armature rheostat at maximum position.

3. Field rheostat at minimum position.

4. Switch on the supply and run the motor at no load.

5. Adjust the field rheostat bring motor speed to rated speed.

6. Note the readings and tabulate the readings

TABULATION

Si

no

Voltage V

(in volts)

𝐼𝑆𝐻

AMPS

𝐼𝐴0

AMPS

𝐼0=𝐼𝐴0 + 𝐼𝑆𝐻



AS MOTOR

Sl No Fraction

of

load(X)

Voltage(v) Current

Ia in

Amps

Total loss=

X²Ia²Ra+Wc

Input

power

o/p

power

efficiency

AS GENERATOR

Sl No Fraction

of

load(X)

Voltage(v) Current

Ia in

Amps

Total loss=

X²Ia²Ra+Wc

Input

power

o/p

power

efficiency

CALCULATIUON

Constant losses Wc= V ( Iao+ Ish)-Iao²Ra.

AS MOTOR

I/p power=F.L o/p Power+Ia²Ra+Wc.,O/p power= V𝐼𝐿, 𝐼𝐿=Ia+ Ish.

Total loss= Ia²Ra+Wc.

O/p=I/p-Losses.

Efficiency=𝑂/𝑝

𝑖/𝑝 x100.

AS GENERATOR

Full load o/p power=Vx𝐼𝐿.

I/p=o/p+ losses.


𝑖/𝑝 x100.

RESULT



LOAD CHARACTERISTICS OF SELF EXCITED DC SHUNT GENERATOR

AIM

To conduct the Load test on the given DC Shunt Generator and plot its internal and external characteristics.

CIRCUIT DIAGRAM

TO FIND Ra



APPARATUS REQUIRED:

SL NO APPARATUS

REQUIRED

SPECIFICATION QTY

MACHINE SPECIFICATIONS

Motor Generator

KW / HP

Volts

Amps

Speed

THEORY

An electric generator is a machine, which converts mechanical energy in to electrical energy. The energy

conversion is based on the principle of the production of dynamically induced emf, whenever a conductor cuts

the magnetic flux; dynamically induced emf is produced in it according to Faraday’s laws of electromagnetic

induction. This emf causes a current to flow if the conductor circuit is closed.


Self excited Generator

SeLF -excited generators are those whose field magnets are energized from the

generator itself.

Eg = V + IaRa in volts. Where,

Eg = Generated voltage in volts.

V = Terminal voltage in volts.

Ia = Armature current in Amps.



Ra = Armature resistance in ohms.

Armature current Ia = IL+ Ish in Amps. Where,

IL = Load current in Amps.

Ish = Shunt field current in Amps.

PROCEDURE:

1. Connect the circuit as per the circuit diagram.

2. Keep the motor field rheostat at minimum resistance and generator field rheostat at maximum resistance

position.

3. Adjust the motor field rheostat for rated speed of the generator (or by voltage control)

4. Fix the armature voltage of the generator to the rated voltage by adjusting the field rheostat of the

generator.

5. Close the DPSTS at the load side of the generator and increase the load in steps till the rated armature

current and at each step the readings of terminal voltage, load current, and shunt field current are noted.

6. Finally reduce the load insteps and bring the generator and field rheostat to its original position.

TO FIND Ra:

1. Connections are given as per the circuit diagram.

2. Gradually vary the loading rheostat insteps and at each step note down the corresponding voltmeter and

ammeter readings.

3. From the tabulated value calculate the average armature resistance.



TABULATION

S. No Load voltage Load current Field current Ia= IL + IF Eg=Va+IaRa

Volts Amps Amps Amps Volts

TO FIND R

S. No Voltage (Va) Current (Ia) Ra=Va/Ia

Volts Amps Ohms



MODEL GRAPH

RESULT



OPEN CIRCUIT OF DC SEPERATELY EXCITED SHUNT GENERATOR

AIM

To obtain the open circuit characteristics of a separately excited DC Generator at rated speed and to

determine Critical field resistance at rated speed

CIRCUIT DIAGRAM

APPARATUS REQUIRED:

SL NO APPARATUS

REQUIRED

SPECIFICATION QTY

MACHINE SPECIFICATIONS:

Motor Generator

KW / HP

Volts

Amps

Speed



THEORY

An electric generator is a machine, which converts mechanical energy in to electrical energy. The

energy conversion is based on the principle of the production of dynamically induced emf, whenever a

conductor cuts the magnetic flux; dynamically induced emf is produced in it according to Faraday’s laws of

electromagnetic induction. This emf causes a current to flow if the conductor circuit is closed.


Separately excited Generator:

Separately -excited generators are those whose field magnets are energized from the External power

supply.Critical field resistance, Rc = Slope of the tangent drawn to the linear portion of the OCC and passing

through origin

PROCEDURE:

1. The connections are given as per the circuit diagram.

2. Verify whether field rheostat of the generator is kept at maximum position and field rheostat of motor at

minimum position.

3. Switch ON the DC supply.

4. Adjust the excitation of field rheostat of the motor so as to make the motor to run at rated speed of the

gemerator (or by voltage control)

5. The ammeter and voltmeter readings of the generator are noted with SPSTS switch in opened position.

6. Close the SPSTS switch and excitation of the generator is varied insteps by adjusting the field rheostat

of the generator, at each step the readings of field current and induced emf are noted up to its rated

generator voltage.

7. The readings are tabulated and a graph of open circuit characteristics is drawn between generated

voltage Vs field current.



TABULATION

S. No Field current

(Amps)

Output voltage at no load

(Volts)

MODEL GRAPH

RESULT



POLARITY TEST AND TURN`S RATIO TEST ON SINGLE PHASE

TRANSFORMER

AIM

To conduct polarity test, and determine turn`s ratio, transformation ratio.

CIRCUIT DIAGRAM



APPARATUSREQUIRED

SL NO APPARATUS

REQUIRED

SPECIFICATION QTY

THEORY

Turns ratio of a transformer = No of turns of primary/No of turns of secondary.

Transformation ratio K = Secondary induced EMF/ Primary induced EMF= E2/E1

E1 = 4.444 φm.f.N1Volts., and E2 = 4.444 φm.f.N2Volts ... K= E2/E1

K =4.444 φm.f.N2/4.444 φm.f.N1 , =N2/N1

...Turns ratio, N1/N2=E1/E2

PROCEDURE

Polarity test.

1 Connections are made as shown in figure (1)

2. Checked the connections and given a specified voltage to primary.



3. Noted the volt meter reading and verified the polarity of the transformer.ie If the voltmeter reading in the

inter connected voltmeter is greater than the input voltage, then the polarity is additive , So Opposite polarity

on the other adjacent terminal on secondary.

4. Interchanged the connections to confirm first determined polarity.

TURNS RATIO AND TRANSFORMATION RATIO TEST

1. Connections are made as in figure (2)

2. Checked the connections and given the supply gradually from minimum voltage to rated voltage of

primary using autotransformer.

3. Noted the V/m readings on primary and secondary

4. Tabulate the readings.

TABULATION

Sl No VOLT

METER

READING VI

VOLT

METER

READING

V2

VOLT

METER

READING

V3

REMARKS Turns

ratio

Transf.

ratio =K

RESULT



CONNECTION OF THREE SINGLE PHASE TRANSFORMERS TO FORM

THREE PHASE BANK

AIM

To connect three single phase transformers to form three phase bank with star-delta connection.

CIRCUIT DIAGRAM

APPARATUS REQUIRED

SL NO APPARATUS

REQUIRED

SPECIFICATION QTY



THEORY

Interconnection of the phase winding to give a three phase ,three or four wire supply provide three

alternative modes of connection 1-mesh or delta 2-star 3-zig-zag and each of these can be achived in two ways

ie,star connection may be had by joining together A1,B1,C1 to form the neutral and using A2,B2,C2 may joined

to give neutral and A1,B1,C1 may be used as line terminal now primary and secondary can be treated in either

two ways

PROCEDURE

1. Mark the terminals of the transformer by conducting polarity test

2. Connect the ends of the primary winding in star and secondary winding in delta through a volt

meter

3. Keep the auto transformer in minimum positon and switch on the supply

4. Adjust the auto transforme to the rated voltage at the primary side

5. Check the voltmeter readings

6. If the voltmeter shows any reading it means that the system is not in balanced condition

7. In this condition,star point is of primary should be earthed and remove the voltmeter and make

the conection

8. Note the primary and secondary line voltage and primary phase voltage

9. Calculate the turns ratio

TABULATION

SL

NO

PRIMARY LINE

VOLTAGE V1 Volt

SECONDARY LINE

VOLTAGE V2 Volt

RESULT

ELECTRICAL MACHINERY LAB (436) - madinpoly.commadinpoly.com/pdf/labmanual/3/ELECTRICAL MACHINERY LAB...

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