EM-II final

8/2/2019 EM-II final

1/57


2/57

SEPERATION OF CORE LOSSES OF 1-PHASE TRANSFORMER

AIM: To separate the core losses of a given single phase transformer.

APPARATUS:

S.NO APPARATUS RANGE TYPE QUANTITY

1.

2.

3.

4.

5.

Voltmeter

Ammeter

Watt meter

Rheostat

Tacho meter

( 0-300)V

(0-5)A

300V/5A L.P.F

570/1.2A290/2.8A18/12A

(0-9999)RPM

THEORY:

Due to rotations of iron core of the armature in the magnitude

flux of the field poles there are some losses taking place continuously in

the core known as iron losses or core losses. The iron losses consists of

1.Hysteresis losses.

2.Eddy current losses.

HYSTERESIS LOSS:

This losses is due to the reversal of magnetization of thearmature core passes under N&S of the rotation pole alternately. The

core under goes one complete cycle of magnetic reversal after passing

under one pair of poles. If P is the number of poles , N is the armature

speed in RPM then frequency of magnitude reversals in

f=PN/120


3/57

The losses depends up on the volume and grade of iron

,maximum value of flux density Bmax and frequency of magnetic

reversals. For normal flux densities,hysteresis losses is given steinmetz

formulae, according to this formulae.

Wh = B1.6

max V watts

V = volume of the core in m3

= steimmetz hysteresis coefficient.

These losses can be minimized by detected proper magnetic materials

which has low hysteresis losses.

EDDY CURRRENT LOSS(We):

When the armature core rotates it also cuts the magnetic flux ,

hence an emf is induced in the body of the core according to the law of

electro magnetic induction this emf through small sets up large current

in the body of the core due its small resistance this current is known as

eddy current .

We = K B2

max f2

t2

v2

watt

Where

Bmax =Maximum flux density.

f =Frequency.

t = Thickness of material.

v = Volume of armature core.

It is seen from above that this loss varies directly as the squire of the

thickness of laminations, Hence it should be kept as small as possible.


4/57

PROCEDURE:

1. Connections are made as per the circuit diagram.2. Keep the motor armature rheostat in maximum position and

motor field rheostat in minimum position.

3. Switch on dc supply to the motor.4. Start the motor with the help of 3-point starter.5. Adjust the speed of the motor to rated value with the help of

motor field &armature rheostat.

6. Now switch on the supply to the excitation of alternator circuitand adjust the alternator field rheostat to rated voltage which is

suitable to Lv side of transformer.

7. Calculate the speed of different frequencies are55HZ,52HZ,47HZ,45HZ etc.

8. Note down the readings of the voltmeter,ammeter,wattmeterandmeasure the speed.

9. Now vary the motor armature rheostat until the motor speed toreduce to required value .

10.Again calculate the speed at different frequencies.11.Note down the readings of voltmeter, ammeter, and wattmeter for

different frequencies.

12.Keep the rheostat to initial position and switch off the supply ofthe excitation of the motor.

CALCULATIONS:

Wi = Af+Bf2

Wi /f = A+Bf

Wi = Core losses or iron losses.

Af = Hysteresis losses.

Bf2= Eddy current losses.

N = 120f / p, poles = 4

Hysteresis losses Wh = Af


5/57

Eddy current losses We = Bf2

Core losses = Wh + We

TABULAR FORM:

s.no Iamps Vvolts Nrpm Fhz Wwatts W/FWatt/hz V/fVolt/hz Wh We

PRECAUTIONS:

1.Avoide loose connections.

2.Take the readings with out parallax error.

3.Double check the circuit before giving the supply.4.The motor armature rheostat in maximum position and motor

field rheostat in minimum position.

RESULT:


6/57


7/57


8/57

NO LOAD &BLOCKED ROTOR TEST ON 3- SLIP RING

INDUCTION MOTOR

AIM:

To conduct no load and blocked rotor test on 3- slip ring

induction motor and find efficiency ,slip for a 3- slip ring

induction motor.

APPARATUS:


1.

2.

3.

4.

5.

Voltmeter

Ammeter

Watt meter

Tacho meter

3- variable

( 0-600)V

(0-10)A

600V/10A

150V/20A

(0-9999)RPM

415/0-470V

THEORY:

The performance characteristics of an induction motor are

derivable from a circular locus. The data necessary to draw the circle

diagram may be found from no-load and blocked rotor test.

NO-LOAD TEST :

The practice , not possible to run the induction motor

synchronous speed. Instead the motor is run with out any external

mechanical load on it. The speed of rotor would not be synchronous but

very much near to it . So that for all practical purpose. The speed may

be assumed synchronous speed.


9/57

The no-load test is carried out rated voltage. The input power

is measured by two wattmeters. Current Io by ammeter and voltage byvolt meter. As the motor is running light load. The power factor would

be low i.e less than 0.5. Hence total power input will be different of two

wattmeter readings W1&W2. The total power will be Wo.

No-load Wo to the rotor consists of ,

1. Small stator cu loss + small rotor loss.

2.Stator core loss.

3. Core due to friction and windage.

Wo = 3VLIocoso

coso = Wo / 3VLIo

BLOCKED ROTOR TEST:

It is a short circuit test. In this rotor is blocked mechanically and

then we applied armature voltage till the ammeter shows the rated

current.

If the normal voltage is applied to the stator, then

ISN = Is X V/VsPower factor on short circuit is found from

Ws= 3Vs Is coss

coss = Ws /3Vs Is


10/57

PROCEDURE:

NO LOAD TEST:

1. Make the connections as per the circuit diagram.2. for the no load test load is not applied on the rotor pulley.3. By varying the 3 Auto transformer, apply the rated voltage.4. Note down the readings of no load voltage, no load current and

wattmeter readings.

BLOCKED ROTOR TEST:

1. Connect the circuit as per the circuit diagram.2. Connect the load at the output terminals.3. Vary the 3 Auto transformer until the ammeter reads the rated

current.

4. Note the readings of voltmeter, Ammeter and wattmeter.

MODEL CALCULATION:

NO LOAD TEST:

WO = W1 +W 2

coso = Wo / 3VLIo

BLOCKED ROTOR TEST:

Wsc = Ws /3Vs Is

Short circuit input current ISN = ISC x VO/VSC

Short circuit input power WSN = 3 VO ISNcossc

Output power = Full load output power/ power scale


11/57

TABULAR FORM:

NO LOAD TEST:

S.NO IO(Amp) VO(Volts) W1(Watts) W2(Watts) W1+ W2

BLOCKED ROTOR TEST:

S.NO Isc(Amp) Vsc(Volts) W1(Watts) W2(Watts) W1+ W2

PRECAUTIONS:



3.Double check the circuit before giving the supply.

4.The motor armature rheostat in maximum position and motor


RESULT:


12/57


13/57


14/57

BREAK TEST ON 3- INDUCTION MOTOR

AIM:

To plot the various performance characteristic curves of a

3- induction motor by conducting the break test on it.

APPARATUS:


1.

2.

3.

4.

Voltmeter

Ammeter

Watt meter

Tacho meter

( 0-600)V

(0-10)A

600V/10A

UPF

(0-9999)RPM

THEORY:

It is a direct test on a induction motor . In this load

applying a brake to the pulley mounted on the motor shaft. The brake

band is fixed ith the help of the belt with spring balance . One end of the

belt is fixed spring balance S1 &other is connected to spring balance S2.The motor is run & the load on the motor is adjusted till it carries its

full load current .

Let S1 ,S2 are readings of balances . The net pull on band due to

friction at the pulley is (S1 -S2) lag Wt or 9.81(W1 -W2)

If r = Radius of the pulley in meters.

N = motor of pulley speed in rpm.Shaft torque Tsh = 9.81 (S1 -S2) r N-M

Output power = Tsh 2N/60 = 2NT/60 Watts.

Input power = VI Watts.


15/57

Slip: The difference between synchronous speed Ns 7 actual speed N of

the motor expressd as a 5 of N is called slip.

% Slip = Ns -N/ Ns x100

Torque: It is proposal to product of armature current and flux.

Ta Ia

PROCEDURE:

1. Make the connections as per the circuit diagram.2. Make sure that motor is at the no-load .3. 3- supply is given to stator by closing TPST switch and start the

motor with the help of star-delta starter.

4. Gradually applying the load on motor pulley step wise increases.5. Take the readings of ammeter, voltmeter,wattmeter, spring

balance and speed of motor for each load.

6. Increase the load up to full load current of the motor and take ofammeter, voltmeter,wattmeter, spring balance and speed of motor

for each load.

7. Supply is switched off after removing the load on motor pulley.8. Calculate torque and efficiency and after calculations graph is

plotted between speed,torque,current,slip,power factor, efficiency

to output.

MODEL CALCULATION:

Torque = 9.81(S1-S2) r n-m

Power factor cos = cos[tan-1 3(W1-W2)/ (W1+W2)]

Efficiency = output/ input x100

Output power = 2NT/60

Input power = W1+W2

%Slip = NS-N/NS


16/57


17/57

TABULAR FORM:

S.NO

V

volts

I

amp

N

rpm

Spring

balance W1 W2 Input

(W )

T

nm Output

(W)

P.f

cos%Slip

S1

kg

S2

kg

PRECAUTIONS:






RESULT:


18/57


19/57

SCOTT CONNECTIONS BY USING TWO 1- TRANSFORMER

AIM:

To study Scott connection and compare currents in the primary

and secondary by drawing vector diagram in balance load and un

balanced.

APPARATUS:


1.

2.

3.

4.

Voltmeter

Ammeter

Load

3- auto transformer

(0-300)V

( 0-600)V

(0-5)A

(0-10)A

3KW

415V/0-470V

THEORY:

This is a connection in which conversion of power 3- to 2- is accomplished with the help of two transformers since it was first

proposed by Charles scott. It is frequently referred to as scott

connection.

One of the transformer has center tap both on primary winding

is known as the main transformer. Other transformer 86.65 tap and isknown as teaser transformer . One end of teaser primary is joined to the

center tap on primary.

Let the teaser transformer secondary supply a current I2T at unity

power factor . If we neglect magnetizing current Io then teaser primary

current.


20/57

I1T = I2T x Transformation ratio

= I2T x N2/3 N1 /2= 2/3 x I2T= 1.15 x I2T

Where K= N2/ N

1= Transformation ratio of main transformer.

The total current I1M in each half of the primary main transformer

consists of two parts . These are given bellow.

1. One part is that which is necessary to balance the main secondarycurrent I2M . Its value is,

I2M = I2M x N2/ N1

PROCEDURE:

1. Connections are made as per the circuit diagram .2. Switch on the 3- power supply by closing TPST switch .3. Auto transformer output voltage is adjusted to supply rated

voltage of 415v to the primary of main and teaser transformer.

4. For the balanced loads apply equal resistance loads across mainand teaser transformer secondary.

5. Record ammeter and voltmeter readings of primary andsecondary.

6. Repeat the process in step wise up to rated load current oftransformer.7. For un balance loads apply .8. record ammeter and voltmeter readings of primary and

secondary.

9. Repeat above step by applying un equal loads at different points.10.Calculate primary current (I1) by consisting of secondary current

(I2) at different loads and compare with readings obtain by phase

diagram and calculations.

MODEL CALCULATION:

K = V2/V1

I2T= P/COS V


21/57

BALANCED LOADS:

Line current IA = I B = I1T2

+ ( IM)2

K of teaser transformer , K = 1.15 = K

IR = I1T = 1.15 K I2T

IB = IY = I1M= ( K I2M )2+(1/2 I1T)

2

UNBALANCED LOADS:

Line current IA = I B = I1T2

+ ( IM)2

K of teaser transformer , K = 1.15 = K

IR = I1T = 1.15 K I2T

IB = IY = I1M= ( K I2M )2+(1/2 I1T)

2


22/57

TABULAR FORM:

BALANCED LOADS:

S.NO VL(V) IR(A) IY(A) IB(A) I2T(A) I2M(A) V2T(V) V2M(V)

UNBALANCED LOADS:

S.NO VL(V) IR(A) IY(A) IB(A) I2T(A) I2M(A) V2T(V) V2M(V)

PRECAUTIONS:




RESULT:


23/57


24/57

REGULATION OF 3- ALTERNATOR BY SYNCHRONOUS

IMPEDENCE & MMF METHOD

AIM:

To find the regulation of 3- alternator by synchronousimpedance &MMF method.

APPARATUS:


1.

2.

3.

4.

Voltmeter

Ammeter

Rheostat

Tacho meter

( 0-600)V

(0-10)A

(0-5)A

360 /1.2A290/2.8A18/12A

(0-9999)RPM

THEORY:

Regulation :

It is clear that with change in load there is a change in

terminal voltage of an alternator . The voltage regulation of an

alternator is defined as the change in voltage when full load is removeddivided by rated terminal voltage .

% Regulation = EoV/VSynchronous impedance method:


25/57

It is also known as emf method .In this method

following procedure steps are.

1. Occ is plotted from given data .2. Similarly Sc is drawn from the short circuit data .It is a straight linepassing through the origin.

E1 = Zs I1

Zs = E1 (open circuit)/ I1 (short circuit)

3. Calculate Xs = Zs 2- Ra24. Eo = (V Cos + IRa )2+ (V Sin +I Xs)25. % Regulation = EoV/V x100

Mmf method:

It is also known as ampere turns method ,In this

method also utilize the oc & sc data. In this method following

procedure steps are involved ,

1.Occ is plotted from given data .2.Similarly Sc is drawn from data. It is a straight line passing

through the origin both these curves are drawn on common base

of field current .

3.Find IFT = If 12 + If 22 2 If 1 If 2 Cos(180-(90+)Take the corresponding readings voltages for IFT

4.% Regulation = EoV/V x100


26/57

PROCEDURE:

OPEN CIRCUIT TEST:

1. Connections are made as per the circuit diagram.2. A dc shunt motor is used as an prime mover to the alternator .3. Start the dc shunt motor (prim mover) by closing DPST switch &

3-point starter.

4. A 220V dc supply is given to field winding as shown in circuitdiagram.

5. By increasing the field rheostat of alternator , note up to ratedline voltage &field current .

6. Draw the open circuit characteristics graph between field current(If) and phase voltage (Eph).

SHORT CIRCUIT TEST:

1. Connections are made as per the circuit diagram.

2. In this method stator winding is short circuited through ammeter.

3. By adjust the rated field current to zero by drawing the field rheostat.

4. By increasing the field rheostat & note down Ifand short circuit

current (ISC).

5. Note down the readings of ISC

& If

up to rated current .

6. Armature resistance is find out by using multimeter.

7. Effective resistance Rac =1.6 xRdc.

8. Draw the graph between ISC & If .

MODEL CALCULATION:

EMF METHOD:

Impedance Zs = V1/I1

Reactance Xs = ZS2

- RAC2

EO = (V cos + IR)2 + (Vsin + I XS)

2

% Regulation = Eo - V/V


27/57

MMF METHOD:

EPH = V + I a Ra cos

If= If12+ If2

2+ 2 If1 If2 cos (180-(90+ ))

TABULAR FORM:

OC TEST:

S.NO If(Amps) EPH(Volts)


28/57

SC TEST:

PRECAUTIONS:




4.The motor armature rheostat in maximum position and motorfield rheostat in minimum position.

RESULT:

S.NO If(Amps) EPH(Volts)


29/57


30/57

OC &SC TEST ON 1- TRANSFORMER

AIM:

To find the regulation and efficiency of a given 1-transformer by conducting oc & sc tests.

APPARATIS:


1.

2.

3.

Voltmeter

Ammeter

wattmeter

( 0-150)V

(0-20)A(0-2)A

150V/5A LPF

150V/20A UPF

THEORY:

The performance of a 1- transformer can be calculated onthe basis of its equivalent circuits. Which contain four main parameters.

The equivalent resistance R01 as referred to primary (or secondary R02)

. The equivalent leakage reactance Xo as referred to primary (or

secondary).These parameters can be easily determined by two tests .

1.Open circuit test.2.Short circuit test.

Open circuit test:


31/57

1. The purpose of this test is to determine no load loss or core loss& no load Io which is helpful in finding Xo Ro.

2. One winding of the transformer which over is convenient butusually high voltage winding is left open and other is connected

to its supply of normal voltage & frequency.3. Wattmeter , voltmeter & ammeter are connected in the low

voltage winding in the present case.

4. With normal voltage applied to the primary normal flux will beset up in the core . Hence normal iron loss will occur . Which are

recorded by the wattmeter.

5. If W is the wattmeter reading then,W =V1 IO CosOCosO = W / V1 IO

I = IO Sin O

Iw = IO COS O

Xo = V1/ I

Ro = V1/ Iw

Short circuit test:

1. This is an economical method for determining the following.2. Equivalent impedance (Z1 or Z02) , leakage reactance (X01 or X02) &

Total resistance (R01 or R02) of the transformer as referred to the

winding in which the measuring instruments are placed.

3.

Copper loss at full load . This loss is used in calculating the efficiencyof a transformer.

4. In this test the one winding is usually the low voltage winding issolidly short circuited by a thick conductor.


32/57

5. Since in this test the applied voltage is a small percentage of thenormal voltage , the mutual flux is also a small percentage of its

normal value.

6. Hence core losses are small with the result that the wattmeterreading represent .The full load copper loss or I2 R loss for the wholetransformer i.e both primary and secondary copper loss.

7. If Vsc is the voltage required to calculate rated load currents thenZ01 = VSC/I1

W = I12R01

R01 = W/ I12

X01= Z012R01

2

PROCEDURE:

OC TEST:

1. Connections are made as per the circuit diagram.2. First make the auto transformer output voltage zero & HV open.3. Give the supply by closing DPST switch &adjust output voltage of

the autotransformer equal to rated LV winding.

4. Note down readings of wattmeter , no-load voltage (Vo) & no-loadcurrent (Io).

SC TEST:

1. Connections are made as per the circuit diagram.2. First make the auto transformer output voltage is zero.3. Adjust the auto transformer output voltage such that rated

current flows in HV side.

4. Take the readings of power , short circuit current & short circuitvoltage.

5.

Calculate the parameters of equivalent circuit , efficiency & %regulation on 1- transformer for given load &power factor.


33/57

MODEL CALCULATIONS:

OC TEST:

Coso

= WO/V

OI

O

Sino = 1- Cos2 o

RO = VO/ IO Coso

XO = VO/ IO Sino

K = V2/V1

SC TEST:

Z02 = VSC /I SC

R02 = WSC / ISC2

X02 = Z022

- R 022

R01 = R02 /K2

X01 = X02 /K2

Efficiency = X KVA Cos/ X KVA Cos + Wi + X2

Wcu X 100

% Regulation = I2 (R02 Cos + X02 Sin)/ V2 X 100


34/57

TABULAR FORM:

OC TEST:

S.NO VO (Volts) IO (Amps) WO (Watts)

SC TEST:

S.NO VO (Volts) IO (Amps) WO (Watts)


35/57

PRECAUTIONS:






RESULT:


36/57


37/57


38/57

SUMPNERS TEST ON PAIR OF 1- TRANSFORMERS

AIM:

To determine the efficiency & regulation of a 1- transformerat different loads by conducting sumpners test.

APPARATUS:


1.

2.

3.

4.

Voltmeter

Ammeter

wattmeter

3- auto transformer

(0-600)V

( 0-150)V

(0-5)A(0-20)A

150V/5A

150V/20A

415V/0-470V

THEORY:This test is also known as back to back test. It provides

data for finding regulation & efficiency under load condi tons and is

employed only when two similar transformers are available . One

transformer is loaded all the other hand both are connected to supply

.The power taken from the supply the supply is that necessary for

supplying the losses of both transformer and are negligible loss in the

control circuit.

When the primary of two transformers are connectedin parallel across the same supply switch S open the wattmeter W1reads core loss of the both transformer .


39/57

Secondarys are so connected that their potentials are inopposite direction to each other. Hence W1 reads the core loss and W2

reads full load copper loss .Applying rated voltage all primary side with

the help of auto transformer . The voltmeter reading s across the switch

it will read zero . But it reads other value than switch OFF the power

supply & reverse the terminals of the transformer.

PROCEDURE:

1. Connections are made as per the circuit diagram.2. Apply rated voltage on primary side with help of auto

transformer.

3. observe that the readings of voltmeter across the switch S iszero or not. If it reads other value than switch OFF the powersupply and reverse the any one of secondary of transformer

terminals.

4. Now close the switch by increase 1- variac from zero positionup to attaining rated secondary current from the secondary

circuit.

5. The readings of two watt meters will directly give the iron &copper loss of both transformer.

6. Note down the voltmeter & ammeter readings of both primarysecondary.

7. Core loss & copper loss of each transformer is calculate bydividing by 2.

8. Calculate regulation of each transformer.MODEL CALCULATIONS:

Coso = WO/VO IO

IW=IO Coso

I= IO Sino


40/57

RO = VO/ IW

XO = VO/I

R02

= RSC

= WSC

/ ISC

2

ZSC = VSC /I SC

X02 = XSC= ZSC2

- RSC2

Efficiency = X KVA Cos/ X KVA Cos + Wi + X2

Wcu X 100


41/57

TABULAR FORM:

S.NO

VO(Volts) I

O(Amps) W

O(Watts) V

SC(Volts) I

sc(Amps) W

sc(Watts)

PRECAUTIONS:






RESULT:


42/57


43/57


44/57

DETERMINATION OF Xd & Xq BY SLIP TEST

AIM:

To determine the values of Xd & Xq by conducting slip test

on 3- salient pole transformer.

APPARATUS:


1.

2.

3.

4.

Voltmeter

Ammeter

Rheostat

Tacho meter

( 0-150)V

(0-5)A

18/12A570/1.2A

(0-9999)RPM

THEORY:

In this test the value of Xd & Xq can be determined by

synchronous machine given by a separate prime movers at a speed

slightly less that synchronous speed. The field winding is left open &

balance voltages of reduced magnitude around 25% of rated value &

rated frequency i.e applied across the armature terminals under this

condition the relative velocity between field poles & rotating armature

.Flux is equal to the difference between the synchronous speed and rotorspeed NsN i.e slip speed .


45/57

At one instant when the peak of armature flux wave is in

line with field poles or direct axiss the reluctance offered by the smallair gap is minimum .At this instant the applied terminals voltage per

phase divided by corresponding armature current per phase gives at

this reactance.

Xd = Vmax/IminAfter one quarter of slip cycle the peak value of the

alternator flux adder all the entire poles or q-axiss of the field poles.The reluctance offered by long reluctance is maximum . At this instant

the ratio of armature terminals voltage per phase to corresponding

armature current per phase to given axis.

PROCEDURE:

1. Connections are made as per the circuit diagram.2. By using the DPST switch give the supply to the motor.3. By varying armature or field rheostat adjust the prime mover speed

less than the synchronous speed.(i.e slip


46/57

S.NO Vmin(Volts) Vmax(Volts) Imin (Amps) Imax (Amps)

PRECAUTIONS:






RESULT:


47/57


48/57


49/57

NO LOAD & BLOCKED ROTOR TEST ON 1- INDUCTION

MOTOR

AIM:

To find the parameters & equivalent circuit of a 1- inductionmotor by conducting no load blocked rotor test on it.

APPARATIS:


1.

2.

3.

Voltmeter

Ammeter

wattmeter

( 0-300)V(0-150 ) V

(0-15)A

(0-10)A

300V/10A LPF

150V/20A UPF

THEORY:

No load test:

Purpose of this test is to deter mine no load loss or core

loss at no load current Io which is helpful for finding Xo & Ro.One winding of the transformer which ever is convenient but

usually high voltage winding is left open and the other is connected to its

supply at normal voltage & frequency . A wattmeter W and voltmeter V& all ammeter are connected .

WO = VO IO COS OCOS O = WO/ VO IO

Magnetizing component I = IO Sin OXo = VO/ I


50/57

Working component Iw = IO COS ORo = VO/ Iw

Blocked rotor test:

It is also known as short circuit test . This test is used to find

1. Short circuit current with normal voltage applied to stator .2. Power factor on short circuit. Both values are used in

construction of circle diagram.

3. Total leakage reactance X01 of the motor as referred to primary .4. Total resistance of the motor R01 as reforod to primary.

PROCEDURE:

NO LOAD TEST:

1. Connections are made as per the circuit diagram.2. Before giving supply , remove the load on the motor.3. Give the 1- supply to the motor circuit and by varying the auto

transformer give the rated voltage in the voltmeter.

4. Note down the no load current & power in ammeter &wattmeter.

BLOCKED ROTOR TEST:

1. Connections are made as per the circuit diagram.2. Before giving supply tightly fix the rotor with the help of belt.3. Give the supply to circuit & varying the ammeter & up to

attaining rated current in the circuit.

4. Note down the readings of voltmeter , ammeter & wattmeter.

MODEL CALCULATIONS:

NO LOAD TEST:

Coso = WO/VO IO

IW=IO Coso


51/57

I= IO Sino

RO = VO/ IW

XO

= VO/I

BLOCKED ROTOR TEST:

R02 = RSC = WSC/ ISC2

ZSC = VSC /I SC

X02 = XSC= ZSC2

- RSC2

R2'

= R01 - R 1

X1 = X 2'= XSC/2

Slip, S = NsNr /Ns

XO/2 =

R2' /2(2-S) =

X 2' /2 =

TABULAR FORM:

NO LOAD TEST:

S.NO VO(Volts)IO(Amps) WO(Watts)


52/57

BLOCKED ROTOR TEST:

S.NO

VSC

(Volts) Isc

(Amps) Wsc

(Watts)

PRECAUTIONS:






RESULT:


53/57


54/57

V AND INVERTED V CURVES

AIM:

To draw the V and inverted V curves of a given

synchronous motor.

APPARATIS:


1.

2.

3.

4.

5.

Voltmeter

Ammeter

Wattmeter

Lamps

Load

( 0-600)V

(0-5)A

(0-10)A

(0-20)A

600V/10A UPF

600V/10A LPF

230V/60watts

250V/3kw

THEORY:

When the power input to the motor is constant the armature

current increases . When the excitation is either decrease or increase

from the normal value . The graphically relation between the armaturecurrent Ia and the excitation current If curves resembles the shape of V

& therefore known as the V-curves of synchronous motor . It is from

that the current drawn by the motor is minimum at unity power factor

is either leading or lagging . Under lagging power factor the

synchronous motor takes lesses field current for a given armature

current as compare to the field current under leading power factor.


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The relationship between power factor &field current . The

curve resembles & shape as inverted V curve . It is known as inverted V

curves of synchronous motor.

PROCEDURE:

1. Connections are made as per the circuit diagram.2. A rated Dc supply is given to the Dc shunt motor is started with

the help of 3-point starter.

3. Adjust the speed of the motor to a rated value by adjusting itsfield rheostat.

4. Exciting field winding of synchronous motor by the Dc supply tothis circuit by closing the DPST switch2.

5. Observe the reading of voltmeter that is the voltage of bus barsbetween the lines.

6. The synchronous motor voltage is meet by voltmeter.7. Adjust the excitation of synchronous motor such that the

voltmeter V1 connected across armature terminals should be

equal to the bus bar voltage.

8. The synchronous motor is acting as a synchronous generator untill its operation ,when synchronization occur that is all the 6-

lamps bright at one time & dark at another time.

9. Adjust the speed of the Dc motor slightly such that the darkperiod of lamp should be more at this condition DPST switch

closed.

10.Now , the supplied Dc motor is taken OFF.11.By this synchronous generator will convert to synchronous motor

& synchronous Dc motor is converted into Dc generators.

12.By changing the excitation (If) the readings of ammeter &wattmeter readings are taken.


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MODEL GRAPHS:

TABULAR FORM:

S.NO If(Amps) W1(Watts) W2(Watts) IA(Amps) Coso


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PRECAUTIONS:






RESULT:

Documents

EM-II final