BASIC ELECTRICAL ELECTRONICS ENGINNERING Lab manual

SHRI VISHNU ENGINEERING COLLEGE FOR WOMEN::BHIMAVARAM(AUTONOMOUS)DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

BASIC ELECTRICAL & ELECTRONICS LABORATORY

II B.TECH - I SEM

LIST OF EXPERIMENTS

PART-A: Electrical Engineering1. Swinburnes Test on DC Shunt Machine (predetermination of efficiency of a given d.c Shunt machine working as motor and generator)

2. OC and SC Tests on 1- Transformer (predetermination of efficiency and regulation at Given power factors)

3. Brake Test on Three-phase Induction Motor (determination of performance Characteristics).

4. Regulation of Alternator by Synchronous impedance method.

5. Speed control of DC Shunt Motor by a) Armature voltage control b) Field flux control

6. Brake Test on DC Shunt Motor

Circuit diagram for Swinburnes Test:

Circuit diagram for Armature Resistance:

Exp no 1 Swinburnes Test on DC shunt machine (Predetermination of efficiency of a given DC Shunt machine working as motor and generator).

Aim: To conduct Swinburnes test on DC shunt motor and predetermine the efficiency of Generator and Motor.

Apparatus Required:

S. NoEquipmentRangeTypeQty

1Ammeters0-2AMC1No

0-2 AMC1No

2Voltmeters0-300VMC1No

3Rheostats250/2AWire wound2No

4Tachometer0-9999rpmDigital1No

5Connecting WiresLS

Name Plate details:

Theory

Swinburnes test:

It is a simple indirect method in which losses are measured separately and the efficiency at any desired load can be predetermined. This test applicable to those machines in which flux is practically constant i.e. shunt and compound wound machines. The no load power input to armature consist iron losses in core, friction loss, wind age loss and armature copper loss. It is convenient and economical because power required to test a large machine is small i.e. only no load power. The effect of commutation are not considered or tested. The iron losses remains constant is insignificant.

Calculations:

Let IL = No Load CurrentIf = Shunt Field currentThen, no load armature current Ia = (IL If)Also let, V is the supply voltage. Therefore, No load power input = IL watts.

In Swinburne's test no load power input is only required to supply the losses. The losses occur in the machine mainly are: Iron losses in the core Friction and windings losses Armature copper loss.Since the no load mechanical output of the machine is zero in Swinburne's test, the no load input power is only used to supply the losses. The value of armature copper loss = (IL If)2 RaHere, Ra is the armature resistance.

Now, to get the constant losses we have to subtract the armature copper loss from the no load power input.

Then, Constant losses WC = V IL - ( IL If)2 Ra

After calculating the no load constant losses now we can determine the efficiency at any load.Let, I is the load current at which we have to calculate the efficiency of the machine.Then, armature current (Ia) will be (I If), when the machine is motoring.And Ia = (I + If), when the machine is generating.Calculation of Efficiency When the Machine is Motoring on Load

Power input = VIArmature copper loss, PCU = I2 Ra = (I If)2RaConstant losses, WC = VIL - (IL If)2 Ra Total losses = PCU + WC

Efficiency of the motor:

Calculation of Efficiency When the Machine is Generating on Load

Power input = VI

Armature copper loss, PCU = I2 Ra = (I + IF)2 Ra

Constant losses, WC = VI0 - (I0 IF)2 Ra

Total losses = PCU + WC

Efficiency of the generator:

Procedure:

1. Connections are made as per the circuit diagrams2. At no load, run the machine at rated speed using field rheostat.3. Note down the readings of If, Ia, IL,V and N.4. Find the armature resistance using V-I method.5. Calculate the efficiency for and motor and Generator.

Observations Tabular Form:

IL ()((IFIAVN

For Ra

S.NOVIRa=V/I

Precautions:

1. Swinburnes test should be conducted on no load.

Result:

circuit diagram:

N2>N1Fig-1 Open Circuit Test

N2