Me 2209 Electrical Engineering Lab Manual

MAILAM ENGINEERING COLLEGE

MAILAM – 604 304

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

ME 2209 – ELECTRICAL ENGINEERING LABORATORY MANUAL

NAME :

ROLL NO. :

CLASS : B.E. / Mechanical - B

YEAR / SEM : II Yr / III Sem

SYLLABUS

ME 2209 – ELECTRICAL ENGINEERING LABORATORY LIST OF EXPERIMENTS

1. Load test on DC Shunt & DC Series motor 2. O.C.C & Load characteristics of DC Shunt and DC Series generator 3. Speed control of DC shunt motor 4. Load test on single-phase transformer 5. O.C & S.C Test on a single-phase transformer 6. Regulation of an alternator by EMF & MMF methods 7. V curves and inverted V curves of synchronous Motor 8. Load test on three-phase squirrel cage Induction motor 9. Speed control of three phase slip ring Induction Motor 10. Load test on single phase Induction Motor 11. Study of DC & AC Starters

CYCLE - 1 LIST OF EXPERIMENTS

1. Load test on DC Shunt motor 2. Load test on DC Series motor 3. O.C.C & Load characteristics of DC Shunt generator 4. Speed control of DC shunt motor 5. Load test on single-phase transformer 6. O.C & S.C Test on a single-phase transformer

CYCLE - 2 LIST OF EXPERIMENTS

1. Regulation of an alternator by EMF & MMF methods 2. V curves and inverted V curves of synchronous Motor 3. Load test on three-phase squirrel cage Induction motor 4. Speed control of three phase slip ring Induction Motor 5. Load test on single phase Induction Motor 6. Study of DC & AC Starters

INDEX

EX. NO. DATE NAME OF THE EXPERIMENT MARKS SIGNATURE

Ex. No. –

LOAD TEST ON DC SHUNT MOTOR

Aim: To conduct the load test on DC shunt motor and draw the performance characteristics. Apparatus Required:

S.No. Apparatus Range Quantity

Name plate details:

Fuse Rating: Fuse Rating = 125% of rated current Formulae used:

1. Input power Pi = (V × I) Watts; V- Input voltage (Volts)

I- Input current (Amps.) 2. Torque, T = [R × (S1-S2) × 9.81] N-m R-Radius of brake drum in meters S1, S2 – tensions of the belt

3. Output power = 60

TN2 ×××π (watts)

N- Speed of the motor in rpm

4. % Efficiency = powerInputpowerOutput × 100

Precautions: 1. The DPST switch must be kept at open position. 2. Make sure that the starter handle is in OFF position. 3. The motor field rheostat should be kept at minimum resistance position at the time of

starting. 4. At the time of starting, there should not be any load connected to motor. 5. While running on load, the brake drum is cooled by pouring water inside the brake

drum. Theory: The shunt motor has a definite no load speed hence it does not run away when load is suddenly thrown off provided the field circuit remains closed. The drop in speed from no-load to full load is small hence this motor is usual referred to a constant speed motor. The efficiency curve is usually of the same shape for all electric motors and generators. The shape of efficiency curve and the point of maximum efficiency can be varied considerable by the designer, though it is advantageous to have an efficiency curve which is fairly flat. So that there is little change in efficiency between load and 25% overload and to have the maximum efficiency as near to the full load as possible. From the curves it is observed that is certain value of current is required even when output is zero. The motor input under no-load conditions goes to meet the various losses, occurring within the machine. As compared to other motors a shunt motor is said to have a lowest starting torque. But this should not be taken off mean that is shunt motor is incapable of starting heavy load. Actually it means that series and compound motor as capable of starting heavy load with les excess of current inputs over normal values then the shunt motor and the consequently the depreciation on the motor will be relatively less. Procedure:

1. Connections are made as per the circuit diagram. 2. The DPST switch is closed and the starter handle is slowly moved from OFF to ON

position. 3. The machine is brought up to rated speed by adjusting the field rheostat after which

its position is not changed. 4. The no load speed, no load current and no load voltage of the motor are noted. 5. The motor is gradually loaded by tightening the belt on the brake drum. 6. The motor is loaded in steps such that in each step, the load current is increased by 1

Amps. 7. In each step, all the meter readings and belt tensions are noted. Also, speed is

measured using tachometer. 8. The motor is loaded upto 125% of full load current. 9. After completion of the experiment, the load on the motor is released by loosening the

belt on the brake drum. 10. The motor is stopped by opening the DPST switch. 11. Calculations are made as shown in model calculations and various performance

characteristic curves are drawn

Circuit diagram:

Model Graph:

% η

Torque

Output Power (W)

IL

Speed, IL,

% η,

Speed

M

30A

DPST SWITCH

A1

A2

L F A 3-point Starter

V

F1

F2

A

(0-30)A MC

(0-300)V mc

185Ω, 1.5A

S2S1

220V DC Supply

Brake Drum

30A

Tabulation:

S. No.

Input Voltage VI (V)

Input Current II (A)

S1 Kg

S2Kg

Torque (Nm)

Speed N(rpm)

Output Power P0(W)

Input Power Pi(W)

% Efficiency

Model calculation: Circumference of the brake drum = cm Radius of brake drum, R = m Torque, T = [R × (S1-S2) × 9.81] N-m

Output power, P0 = 60

TN2 ×××π (Watts)

Input power, Pi = V x I (Watts)

% Efficiency = powerInputpowerOutput × 100

Result:

Ex. No. –

LOAD TEST ON DC SERIES MOTOR

Aim: To conduct the load test on DC series motor and draw its performance characteristics. Apparatus Required:


Name plate details:

Fuse Rating: Fuse Rating = 125% of rated current Formulae used:

1.Input power = (V × I) Watts V- Input voltage (Volts)

I- Input current (Amps.) 2.Torque, T = [R × (S1-S2) × 9.81] N-m R-Radius of brake drum in meters S1, S2 – tensions of the belt

3.Output power = 60




Precautions: 1. The DPST switch must be kept at open position. 2. Make sure that the starter handle is in OFF position. 3. The motor field rheostat should be kept at minimum resistance position at the time of starting. 4. At the time of starting, there should not be any load connected to motor. 5. While running on load, the brake drum is cooled by pouring water inside the brake drum.

Theory: The drop in speed with increased load is much prominent in series motor than in a shunt motor hence a series motor is not suitable for application requiring a substantially constant speed. For a given current input a starting torque developed by a series motor is greater than that developed by a shunt motor. Hence series motors are used where huge starting torques are necessary that means for cranes and traction purpose. In addition to huge starting torque there is another unique characteristic of series motor which makes this especially desirable for traction work that means when a load comes on a series motor it response by decreasing its speed and supplies the increased torque with a small increase in current. On the other hand a shunt motor under the same condition would hold its speed nearly constant and would supply the required increased torque with a large increase of input current. Procedure:

1. Connections are made as per the circuit diagram. 2. The DPST switch is closed and the starter handle is slowly moved from OFF to ON position. 3. The machine is brought up to rated speed by adjusting the field rheostat after which its position is not changed. 4. The no load speed, no load current and no load voltage of the motor are noted. 5. The motor is gradually loaded by tightening the belt on the brake drum. 6. The motor is loaded in steps such that in each step, the load current is increased by 1 A. 7. In each step, all the meter readings and belt tensions are noted. Also, speed is measured using tachometer. 8. The motor is loaded upto 125% of full load current. 9. After completion of the experiment, the load on the motor is released by loosening the belt on the brake drum. 10. The motor is stopped by opening the DPST switch. 11. Calculations are made as shown in model calculations and various performance characteristic curves are drawn.

Circuit diagram:

MODEL GRAPH

Tabulation:

S. No.

Input Voltage VI (V)

Input Current II (A)

S1 Kg

S2Kg

Torque (Nm)

Speed N(rpm)

Output Power P0(W)

Input Power Pi(W)

% Efficiency

% η

Torque

Output Power (W)

IL

Speed, IL,

% η, T

Speed

M

30A

DPST SWIT

A1

A2

L2-point Starter

V

F1 F2A

(0-30)A MC

(0-300)V MC

S2S1

A

220V DC S l Brake Drum

30A

Model calculation: Circumference of the brake drum = cm Radius of brake drum, R = m Torque, T = [R × (S1-S2) × 9.81] N-m

Output power, P = 60

TN2 ×××π (Watts)

)

0

Input power, Pi = V x I (Watts

% Efficiency = powerInputpowerOutput × 100

Result:

Ex. No. –

OCC AND LOAD CHARACTERISTICS OF A DC SHUNT GENERATOR

im: o determine the load characteristics and open circuit characteristics of a DC shunt generator.

Required:

S.No.

AT Apparatus

Apparatus Range Quantity

Name plate details: Generator Motor Fuse Rating:

use Rating = 125% of rated cu ent

ormulae: Eg = VL+ IaRa (V)

initially. 2. Motor field rheostat must be kept at minimum resistance position. 3. Generator field rheostat must be kept at maximum resistance position.

enerator should be at no load at the time of starting.

F rr F Precautions:

1. All the switches are kept open

4. The g

TheA D duce voltage depending on

hether excitation circuit consumes power for the armature of the machine or from parately require power supply. Generators may be classified as self excited or separately

xcited generators respectively.

he induced emf in DC generators is given by the equation PфZN/60A volts. State P,Z,A are the above equation are written as Eg= KфN. I f the speed of the generator also

en circuit characteristics of the DC generator. The typical ape of the characteristics is shown in fig.

ed the OCC at a different speeds can also be btained. .Critical speed is minimum speed below which the generator shunt fails to excite.

pen Circuit Characteristics:

4. Adjust the field rheostat of the motor and make the motor to run at rated speed. down the corresponding field current and generating emf by varying the field

oad Characteristics:

rents are noted down. loaded up to rated load current.

Arm.

voltage and the load current are determined.

ory: C generator requires an excitation circuit to generate an in

wsee Tconstants maintained constant then Eg = Kф but the flux is directly proportional to the current Hence Eg = K2If. From the above equation it is clear that the induced emf is directly propositional to the field current when speed maintained constant,. The plot between the induced emf and the field current is known as opsh The induced emf when the field current is zero is known as residual voltage. This emf is due to the presence of a small amount of flux detained. In the field poles of the generator called residual flux. Once the OCC is obtained parameters such as critical field resistance, critical speed and the maximum voltage to which the machine can build up can be determined. If requiro Procedure: O

1. Connections are made as per the circuit diagram. 2. Observing the precautions close the DPST switch. 3. The motor is started with the help of three point starter.

5. Note rheostat of the generator.

L

1. Set the generator output at rated voltage. 2. Close the DPST switch on the generator side. 3. The No load reading is noted down 4. The load is included on the generator side in steps and corresponding load voltages

load currents and field cur5. The generator is

ature Resistance Test:

1. The connections are given as per the circuit diagram2. By varying the load rheostat the load3. Thus the armature resistance can be determined.

Ra= Va / Ia.

Cir t

.C.C AND LOAD CHARACTERISTICS OF DC SHUNT GENERATOR

cui Diagram:

O

ARMATURE RESISTANCE TEST:

V 230V DC Supply

+

-

A

(0-10) A MC

MC

Fuse=30A

Fuse=30A

DPST SWITCH

(0-30)V MC

G

A1

A2

1-Ф 230V, 5KW Loading Rheostat

M

Fuse=30A

DPST SWITCH

A1

A2

L F A

3-point Starter

F1

F2

185Ω, 1.5A

230V DC Supply

Fuse=30A

G

A1

A

185Ω, 5A 1.

V

Fuse=30A

(0-300)V mc

DPST SWITCH

A

(0-30)A mc

Fuse=30A

(0-2)A mc

5KW, 230V, Resistive Loading

F1

A2 F2

Model Graph

Tabular column:

.C.C Test

o. Field Current

If(A) Induced Emf

Eg (V)

OS.

N

oad Test L

odel calculation:

S. No.

Load Current IL(A)

Load Voltage VL(V)

Field Current If (A)

Armature currentIa (A)

Induced Emf Eg (V)

M Result:

O.C characteristics

If (A), Ia (A)

Residual Voltage

Eg

Internal characteristics External characteristics

Ex. No. –

SPEED CONTROL OF DC SHUNT MOTOR :

unt motor by field and armature control method.

A a


AimTo obtain the speed characteristics of DC sh

pp ratus Required:

ame plate details:

N

Fuse Rating: Fuse Rating = 125

1. The DPST switch must be kept at open position. e starter handle is in OFF position.

3. The motor field rheostat should be kept at minimum resistance position at the time of arting.

4 The armature rheostat should be kept at maximum resistance position. Theory: Flux Control method:

The speed of the DC motor is inversely propositional to the flux per pole, when the arma re voltage is kept co stant. By decrea ng the flux the speed can be increased and vice versa. Hence the main flux of field control method the flux of a DC motor can be changed y changing field current with help of a shunt field rheostat. Since shunt field current is

unt field rheostat has to carry only a small amount of current which all so that rheostat is small in size .This method is very efficient.

% of rated current Precautions:

2. Make sure that th

st.

tu n si–brespectively small sh

eans I2R losses is smm

Armature Control method: This me od is used when speed below e no load speed are required.As the supply

voltage is norm ly constsnt the voltage across the armature is varied by inserting a variable rheostat in series with the armature circuit. A is increased potential difference across the armature is decreased, herby decreasing the armature speed. F or a load of constant torque speed is approximately prop itional to the potential difference across the rmature.

adjusting the field rheostat, the field current is fixed at one constant value. ying the armature rheostat and

Fie

value. 2. The field current is varied in steps by varying the field rheostat and corresponding

s are noted.

th thal

s conductor resistance

osa Procedure:

rmature Control Method: A1. By 2. The armature voltage is varied in steps by var

corresponding motor speeds are noted. 3. This procedure is repeated for different field current and readings are tabulated.

ld Control Method: 1. By adjusting the armature rheostat, the armature voltage is fixed at one constant

motor speed3. This procedure is repeated for different armature voltage and readings are

tabulated. Circuit Diagram: SPEED CONTROL OF DC SHUNT MOTOR

Model a

control Field Control

Tabular Column: Armature Voltage Control Method:

If1 = (A) If2 = (A)

Gr ph: Armature

S. No. Armature Voltage Va (V) Speed N(rpm) Armature Voltage

Va (V) Speed N(rpm)

Field Control Method:

Va1 = (V) Va2 = (V) S. No. Field current

If (A) Speed N(rpm) Field current If (A) Speed N(rpm)

Result:

Speed N (rpm)

Field Current If (A)

Va1

Va2

Va1 > Va2Speed N (rpm)

Armature Voltage Va (V)

If1 If2

If2 > If2

Ex. No. –

LOAD TEST ON SINGLE PHASE TRANSFOR

im: o conduct load test on single phase transformer and to draw its efficiency and regulation.

Apparatus Required:


MER

AT

Name plate details:

Fuse Rating:Fuse Rating

1. % Efficiency =

= 125% of rated current

Formulae used:

I

o

WW

× 100

2. % Regulation = o

Lo

VVV −

× 100

where, WO - (VL IL) Output power (Watts) WI - Input power (Watts)

VO - No load voltage (Volts) VL - Load voltage (Volts)

×

Precautions:

1. All the switches are kept open initially. 2. Before giving supply, the autotransform3. Initially no load should be connected on e secondary side of the transformer.

Procedure:

1. Connections are made as per the circuit diagram. 2. Supply is given by closing the DPST switch.

dings of Voltmeter, Ammeter and Wattmeter are noted for no load condition. steps and the corresponding voltmeter, ammeter and

5. The load is applied upto rated secondary current. ciency and Regulation in % are calculated and their related graphs are

Circuit LOAD T T AS RANSF

er is kept at zero output voltage. th

3. The rea4. Then the load is applied in

wattmeter readings are noted down.

6. Then Effirawn. d

Diagram:

ES ON SINGLE PH E T ORMER 5 00V, 20A UPF

230V, 50Hz 1Ø Supply

230V/115V 2KVA rmer Transfo

P

N

A

(0-5) A MI

MI

Fuse=10A

Fuse=10A

DPST SWITCH

(0-300)VMI

V

M

C

L

V

Fuse =20A

V

DPST SWITCH

A

(0-20) A MI

1-Ф 230V, 5KW Loading Rheostat

(0-3 00) V MI

N.LFuse =20A

MODEL GRAPH:

Tabulation: S.

o Load Voltage (VL)

Load Current (IL)

Input power WI (W)

Output power WO (W)

%Efficiency %Regulation

% η

N

Model calculation: Result:

Output Power (W)

% η %Regulation %Regulation

Ex. N

OPEN CIRCUIT AND SHORT CIRCUIT TEST ON SINGLE PHASE TRANSFORMER

Aim: To conduct open circuit and short circuit test on single phase transformer and to predetermine its efficiency. Apparatus Required:


o. –

Name plate details:

use RatinFF

g: u

* KVA rating * Cosφ (W) = fraction of load

Cos

2 Losses=WO+x2 WSC ) where WO =open circuit power WSC =Short circuit power

3 Power input= power output +losses (W)

se Rating = 125% of rated current

Formulae used: To predetermine % efficiency

1. Power output=x where x

φ = Power factor . (W

.

powerInputpowerOutput4 % Efficiency = . × 100

5. Equivalent Resistance referred to secondary R2e = Wsc/ Isc2

2e = V / I

7. Equivalent Reactance referred to secondary X2e =

6. Equivalent Impedance referred to secondary Z sc sc

( )22

22 ee RZ −

8. % Regulation (leading) = 2

2222 sincosV

XIRI ee φ ± φ

‘+’ for lagging power factor loads and ‘-‘ for leading power factor loads

Precautions:

1. All the switches are kept open initially. ormer is kept at zero output voltage.

ed out at rated current.

heory:

ine no load loss or core loss and no load current I0 which is

One enient but usually HV winding is kept open and the other is connected to its supply of normal voltage and frequency. A wattmeter W, voltmeter and ammeter A are connected in the present case. With normal voltage applied to the prim l f il et up in the cores hence normal iron losses will occur which are imary no load current Io is small. Cu loss is negligibly meter reading represents the core loss under no load It should be noted that since I0 is very small, the pressure coils of wattmeter and the voltm the current in these do not pass through the current coil of wa Pro

2. Before giving supply, the autotransf3. Open circuit test must be carried out at rated voltage. 4. Short circuit test must be carri

T The purpose this test is to determhelpful in finding X0 and R0.

winding of the transformer whichever is conv

ary norma lux w l be s recorded by the wattmeter. As the pr

small in primary. Hence the watt conditions.

eter are connected such thatttmeter.

cedure: Op

r the circuit diagram. 2. totransformer is adjusted until the voltmeter

ary, keeping the secondary terminals of the

the rated voltage is applied, the corresponding ammeter (IO) and wattmeter O adings are noted.

he core loss of the transformer. culated.

en Circuit Test: 1. Connections are made as pe

For conducting open circuit test, the au primreads the rated voltage (VO) of the

transformer open. 3. When

(W ) re4. The wattmeter reading (WO) is equal to t5. The parameters excited resistance (RO) and excited reactance (XO) are cal

Short Circuit Test:

rcuit test, the autotransformer is adjusted until the ammeter reads the rated current (ISC) of the primary, keeping the secondary terminals of the

ing graphs are drawn. 7. Finally the equivalent circuit of the transformer is drawn.

ram:

IT TEST ON SINGLE PHASE TRASFORMER

1. Connections are made as per the circuit diagram. 2. For conducting short ci

transformer short circuited. 3. When full load current flows in the short circuited transformer, the corresponding

voltmeter (VSC) and wattmeter (WSC) readings are noted. 4. The wattmeter reading (WSC) is equal to the full load copper loss of the transformer. 5. The parameters excited ZO1, RO1 & XO1 are calculated. 6. From above calculations, the efficiency of the transformer are calculated and the

correspond

Circuit diag OPEN CIRCU

Fuse=10A

Fuse=10A

DPST SWITCH

Autotransformer 1KVA

P

N


L

300V, 2A LPF

Transformer 230V/110V

2KVA

(0-2) A MI

A

(0-300)VMI

V

M

C V

SHORT CIRCUIT TEST ON SINGLE PHASE TRASFORMER

Tabular Column: (i) Open circuit test: Rated voltage =---- ------ (V)

No load power W atts)

Model Graph

--

O(WS. No. No load voltage VO(V) No load current IO(A)

Reading Power

% η

Output Power (W)

% η %Regulation %Regulation

Fuse=10A

Fuse=10A

DPST SWITCH

Autotransformer 1KVA

P

N


L

75V, 10AUPF

(0-10) A MI

M A

(0-75)V MI

C V

V

Transformer 230V/110V

2KVA

(ii) Short circuit test: Rated current =------------ (A)

Short circuit power WO(Watts)

S. No. Short circuit voltage VSC(V)

Short circuit current ISC(A)

Reading Power

(iii) Pre determination of % efficiency:

Model calculation:

Result:

S. No.

Load ‘x’

Core Loss

WO(W)

Copper Loss

x2Wsc(W)

Total Loss

Output Power

Input Power

%Efficiency

(iii) Pre determination of % Regulation:

%Regulation S. No. ower FactorcosΦ Leading Lagging

P

Ex. No. – REGULATION OF ALTERNATOR BY EMF AND MMF METHODS

Aim: To pre-determine the voltage regulation of an alternator by using EMF and MMF methods. Apparatus Required:


Name plate details: Alternator Motor Fuse Rating: DC motor = 125% of rated current Alternator = 125% of rated current Formulae used:

1. % Regulation = 100×−

VVEo

Where Eo = No load voltage V = Terminal voltage

2. Synchronous Impedance, Zs = )(Ωsc

o

IE

Where Eo = No load voltage

Isc = Short circuit current

3. Reff = 1.6 Ra

Where Ra = Armature resistance (DC value) Reff = Effective resistance

4. Synchronous Reactance, Xs = 22as RZ −

Where Xs = Synchronous Reactance Zs = Synchronous Impedance Ra = Armature resistance (DC value) 5. Eo = 22 )sin()cos( saaa XIVRIV ±++ φφ Where ‘+’ sign is used for lagging load ‘–’ sign is used for leading load Precautions:

1. The Motor field rheostat must be kept at the minimum resistance position at the time of starting.

2. The generator field rheostat must be kept at the maximum resistance position. 3. Three point starter should be kept at the off position initially.

Procedure: Open Circuit Test:

1. Give the connections as per the circuit diagram. 2. Close the DPST switch on the supply side. 3. The speed of DC motor is adjusted to rated speed by using the motor field

rheostat. 4. Keeping the TPST switch open on alternator side vary the alternator field current

in convenient steps till rated field current of alternator. 5. Note the corresponding values of alternator field current and alternator voltage. 6. Bring the alternator field rheostat to the original position.

Short Circuit Test:

1. The same circuit is used. 2. The rotor TPST switch is closed. 3. The field current of the alternator is slowly increased from zero to the rated

current of the alternator by adjusting the field rheostat of the alternator. 4. The field current corresponding to the rated current of the alternator is alone noted

in tabular column. 5. Reduce the field current of the alternator to zero. 6. Now open all the switches.

Armature resistance test:

1. Connections are made as per the circuit diagram.

2. The control resistance is initially kept at either maximum resistance or open position.

3. Observing the precautions the DPST switch is closed 4. The readings of ammeter and voltmeter are noted. 5. The ratio of Va to Ia gives the value of armature resistance (Ra).

Circuit diagram:

Regulation of alternator by EMF and MMF method

Armature resistance test

Tabulation: Open circuit test Short circuit test

S.

No.

Terminal Voltage VOC

(V)

Field Current If

(A)

Measurement of Stator Resistance

S. No.

Armature Current ISC

(A)

Field Current If

(A)

Armature Resistance Ra =Va/Ia

(Ω)

Armature Voltage Va (V)

Armature Current Ia

(A)

S. No.

Ra =_____ Ω

EMF method:

Eo %Regulation Power factor

Cos Φ

Sin Φ

S. No.

lagging leading lagging leading

0

0.2

0.4

0.6

0.8

1.0

MMF method:

Total field current No- load phase voltage, E0

% Regulation S.No Power factor

Cos Φ

Lagging pf

Leading pf

Lagging pf

Leading pf

Lagging pf

Leading pf

0 0.2 0.4 0.6 0.8 1.0

Model calculation: EMF method: Reff = 1.6 Ra = 1.6 * ____ = Plot the OCC and SCC on common If

Synchronous Impedance, Zs = )(Ωsc

o

IE

Synchronous Reactance, Xs = 22as RZ −

I - full load current V – Ratede terminal voltage phase value Cos Φ – power factor No load induced emf Eo = 22 )sin()cos( saaa XIVRIV ±++ φφ + for lagging power factor load - for leading power factor load

% Regulation = 100×−

VVEo

MMF method: If1 = field current corresponds to rated phase voltage from OCC If2 = field current corresponds to rated current from SCC Total field current If is If = If1

2 + If22 ± 2 If1 If2 cos (90 – Φ)

Where + for lagging power factor load - for leading power factor load Read E0 - noload phase voltage from OCC curve corresponds to the total field current If calculated.

% Regulation = 100×−

VVEo

Result:

Ex. No. –

V AND INVERTED V CURVES OF SYNCHRONOUS MOTOR

Aim: To draw the V and inverted V curves of synchronous motor. Apparatus Required:


Name plate details:

Fuse Rating: Fuse rating = 125% of rated current Formulae used: Power P1 = W1 + W2 (Watts) Where W1 - Actual Wattmeter reading in R-phase W2 - Actual Wattmeter reading in B-phase Cos Φ = P1 / ( √3 VL IL ) P1 - Power VL - Load voltage IL - Load current

Precaution: Procedure:

1. Connections are given as per the circuit diagram. 2. Supply is switched on by closing the TPST switch. 3. A very minimum field excitation is applied to the synchronous motor using the

potential divider or field rheostat. 4. Gradually in cases the load from zero value to any minimum value and keep it

constant throughout the experiment. 5. Vary the field excitation such that the load current ammeter reading decreases to a

minimum value and once again increases. For every excitation note down corresponding readings of all the meters.

6. Decrease the field excitation and load to zero. 7. Switch off the supply.

W1 (watts) W2 (watts)

S.No Field

current If (A)

Load current IL (A)

Load voltage

VL (volts)

Observed reading

Actual reading

Observed reading

Actual reading

P1(watts) Cos Φ

Model graph:

Circuit diagram:

Model Calculation: Result:

Ex. No. –

LOAD TEST ON 3 - PHASE SQUIRREL CAGE INDUCTION MOTOR

Aim: To conduct the load test on 3 phase induction motor and draw the performance characteristics. Apparatus Required:


Name plate details:

Fuse Rating: Fuse rating = 125% of rated current Formulae used:

1. Input power, Pi = (W1 + W2) watts; 2. Torque, T = [R × (S1-S2) × 9.81] N-m R-Radius of brake drum in meters S1, S2 – tensions of the belt





5. % Slip = s

s

NNN −

Where Ns = Rated speed (rpm) Nr = Actual speed (rpm)

6. Power factor = Cos ⎟⎟⎠

⎞⎜⎜⎝

⎛⎥⎦

⎤⎢⎣

⎡+−−

21

211 3tanWWWW

Precautions:

1. The TPST switch must be kept at open position at the time of starting. 2. At the time of starting, there should not be any load connected to motor. 3. The Star-Delta starter must be in OFF position.

Procedure:

1. Connections are made as per the circuit diagram. 2. The TPST switch is closed and the motor is started using Star-Delta starter. 3. The No-Load meter readings and speed are noted. 4. The load is increased gradually and for each load, the corresponding readings and

speed are noted. 5. The above procedure is repeated till the current reaches slightly above the rated

current. 6. The load is reduced to zero and TPST switch is opened.

Model Graph:

% η

Power factor

IL

Torque

Output Power (W)

% slip

Power factor, IL,

% η, Torque, % slip Speed

Speed

Tabulation:

Input Power Pi(W) Tension in belt

W1 W2S.

No.

Load Voltage VL (V)

Load Current IL

(V)

Reading Power Reading Power

Speed N

(rpm)

T1 T2 T(Nm) T1~T2

Output Power P0(W)

Power factor

% Efficiency

% Slip

Circuit diagram:

LOAD TEST ON 3 PHASE SQUIRREL CAGE INDUCTION MOTOR

Model calculation: Result : Thus the load test on 3 - phase induction motor was conducted and its various performance characteristics curves are drawn.

Ex. No. –

LOAD TEST ON SINGLE - PHASE INDUCTION MOTOR

Aim: To conduct the load test on single - phase induction motor and to draw the performance characteristics. Apparatus Required:


Name plate details:

Fuse Rating: Fuse rating = 125% of rated current Formulae used:

1. Input power = W (watts) 2. Torque, T = [R × (S1-S2) × 9.81] N-m R-Radius of brake drum in meters S1, S2 – tensions of the belt





5. % Slip = s

s

NNN −

Where Ns = Rated speed (rpm) Nr = Actual speed (rpm)

6. Power factor (Cos Ф) = LL IV ×

W

Where VL – Load Voltage IL – Load current

Precautions:

1. The DPST switch must be kept at open position. 2. At the time of starting, there should not be any load connected to motor.

Procedure:

1. Connections are made as per the circuit diagram. 2. The DPST switch is closed. 3. The autotransformer is adjusted to get rated voltage and corresponding no load

readings are noted down. 4. Gradually increase the load and for each load the corresponding meter readings

are tabulated. Circuit diagram:

Tabulation:

Input Power Pi(W) Tension in belt S. No.

Load Voltage VL (V)

Load Current IL (A) Reading Power

Speed N (rpm)

T1 T2 T(Nm)

Output Power P0(W)

Power factor % Efficiency %

Slip

Model calculation: Model Graph:

% η

Power factor

IL

Torque

Output Power (W)

% slip

Power factor, IL,

% η, Torque, % slip Speed

Speed

Result: Thus the load test on single - phase induction motor was conducted and its various performance characteristics curves are drawn.

Documents

Me 2209 Electrical Engineering Lab Manual