AIMS
To provide the student with an opportunity to acquire knowledge, skills and attitude in the area of alternating current machines with special emphasis on :
 power transformer.
 auto transformer.
 3phase induction motor.
SHORT DESCRIPTION
Transformer : principle of operation & construction, emf equation, transformation ratio, losses, equivalent resistance, leakage reactance, tests, regulation, efficiency, three phase connection, auto transformer, parallel operation, Threephase induction motor: working principle, construction, magnetic field, torque, power stage, tests, starting and speed control.
DETAIL DESCRIPTION
Theory:
TRANSFORMER

Understand working principle and construction of transformer.
 Define transformer.
 Explain the working principle of transformer.
 Describe the construction of a transformer.
 Identify the materials used in transformer construction.
 List different types of transformers.
 Describe core type, shell type and spiral core type transformer.
 Compare the core type and shell type transformer.

Understand the emf equation.
 Define emf equation.
 Express the derivation of emf equation.
 Solve problems on emf equation.

Understand the transformation ratio.
 Explain voltage ratio and current ratio.
 Explain turns ratio.
 Solve problems on transformation ratio.

Understand different losses of transformer.
 List the losses in transformer.
 Explain hysteresis loss, eddy current loss and core loss.
 Explain copper loss.

Understand the principle of operation of transformer on noload condition.
 Explain noload operation of transformer.
 Define noload voltage, current, mutual flux, no load power factor.
 Draw the vector diagram of transformer on no load.
 Solve problems related to no load test.

Understand the principle of operation of transformer on load condition.
 Explain operation of transformer on load.
 Draw the vector diagram of transformer on lagging, leading and unity power factor load condition.
 Solve problems related to transformer on load.

Understand the open circuit test and short circuit test of transformer
 Describe open circuit test.
 Describe short circuit test.
 Draw vector diagram.
 Solve problems related to short circuit test.

Understand the equivalent resistance, magnetic leakage and leakage reactance of transformer.
 Deduce the equivalent resistance of transformer as referred to primary.
 Deduce the equivalent resistance of transformer as referred to secondary.
 Explain magnetic leakage of transformer.
 List the disadvantages of magnetic leakage.
 Deduce equivalent resistance & leakage reactance of transformer in terms of primary and in terms of secondary.
 Solve problems on equivalent resistance, leakage reactance and impedance of transformer.

Understand equivalent circuit of transformer.
 Draw the equivalent circuit of transformer.
 Explain the equivalent circuit of transformer.
 Draw the equivalent vector diagram of transformer.

Understand the voltage regulation of transformer.
 Define voltage regulation.
 Express the deduction of the equation for voltage regulation at unity, lagging and leading power factor load.
 Solve problems related to regulation.

Understand the percentage resistance, reactance & impedance.
 Define percentage resistance, reactance and impedance.
 Express the deduction of the equation for percentage resistance, reactance and impedance.

Understand the efficiency of transformer.
 Express the deduction of the formula for calculation of efficiency of transformer.
 Explain the factors affecting core loss and copper loss of the transformer.
 Express the deduction of the equation for maximum efficiency.
 Evaluate the variation of efficiency with power factor.
 Explain all day efficiency.
 Solve problems on efficiency and maximum efficiency.
 Solve problems on all day efficiency.

Understand the cooling of transformer.
 Explain the necessity of cooling of transformer.
 Describe the methods of cooling the transformer.
 Describe the transformer oil and its properties.

Understand the construction and principle operation of three phase transformer.
 Describe the construction of three phase transformer.
 Describe the different parts of a three phase transformer.
 List various methods of connection of 3phase transformer.
 Describe the methods of star – star, delta – delta, star – delta and delta – star connection.
 Describe the application of the above methods.
 Describe open delta connection or VV connection.
 Describe scott or TT connection.
 Explain the application of VV and TT connection.
 Draw the connection of 3phase to 2phase
 Draw the connection of 2phase to 3phase.

Understand the principle of autotransformer.
 Describe autotransformer.
 Explain the terms transformed power and conducted power.
 List the advantages and disadvantages of autotransformer.
 Convert a 2winding transformer to autotransformer.
 Mention the uses of autotransformer.
 Solve problems on autotransformer.

Understand the principle of parallel operation of transformer.
 Explain the purpose of parallel operation.
 List the conditions for parallel operation.
 Explain the purpose of polarity test.
 Describe the subtractive and additive polarity.
 Describe the test to determine the polarity of a transformer.
 Describe the parallel operation of transformers with equal voltage ratio.
 Solve problems related to parallel operation.
 List the conditions for parallel operation of 3phase transformer.
 List the standard ratings of transformer.
 Explain the specification on the name plate of a transformer.
THREE PHASE INDUCTION MOTORS.

Understand the principle and construction of 3phase induction motor.
 Explain the general principle of induction motor.
 Distinguish between induction motor and conduction motor.
 List various types of induction motor.
 List different parts of a 3phase induction motor.
 Describe the construction of stator of an induction motor.
 Describe the construction of squirrel cage rotor, double squirrel cage rotor and wound rotor of induction motor.
 Explain the purpose of skewing the rotor bars in a squirrel cage rotor.
 Define slip and slip speed.
 Express the derivation the equation = sf and
 Explain rotor voltage, rotor current and rotor power.
 Mention the uses of induction motor.
 Solve problems related to slip. .

Understand the concept of development of rotating magnetic field.
 Explain the development of rotating magnetic field for three phase induction motor in 3phase supply.
 Express the deduction of the formula .
 Explain the principle of rotation of a 3phase motor.

Understand the principle of torque developed in rotor.
 Explain starting torque, running torque and maximum torque.
 Express the deduction of the equation of starting torque, running torque and maximum torque.
 Describe the condition for maximum torque for running and starting condition.
 Mention the relation between torque and rotor power factor.
 Explain the relation between torque and speed.
 Draw the torque speed curve.
 Explain the effect of changing the voltage on torque and speed.

Understand the concept of power stages of induction motor.
 List the losess in 3phase induction motor.
 Indicate different stages of power developed in an induction motor in a diagram.
 Solve problems on power distribution.

Understand the equivalent circuit and maximum power output of an induction motor.
 Draw the equivalent circuit of an induction motor.
 Explain the circuit diagram.
 Explain maximum power output of an induction motor.
 Express the deduction of the maximum power output

Understand the principle of starting of a 3phase induction motor.
 Explain the purpose of starter.
 List the starters used for starting 3phase induction motor.
 Describe the direct online starter method, startdelta starter method (manual and automatic), auto transformer starter method of starting squirrel cage induction motor.
 Describe the rheostat method of starting slip ring induction motor. .

Understand the principle of speed control of induction motor.
 List the methods of speed control of 3phase induction motor.
 Describe speed control by changing applied voltage, changing applied frequency and changing stator poles.
 Describe rheostat control method, concatenation method & injecting emf in rotor circuit.
Practical:

Determine the transformation ratio of a single phase transformer.
 Sketch the required circuit diagram.
 List the tools, equipments & materials for the experiment.
 Connect the equipment according to the circuit diagram.
 Apply the voltage to the high side and connect the load to the low side.
 Tabulate the readings from the instruments and calculate the transformation ratio from the formula:

Determine the voltage regulation of single phase transformer by direct loading.
 Sketch the necessary circuit diagram.
 List the tools, equipment & materials required.
 Connect the meters according to the diagram.
 Connect the source to the primary keeping the secondary open and record no load voltage (V_{o}).
 Connect full load on the secondary & record the load voltage.
 Calculate the voltage regulation from the formula:
% Voltage Reg. =

Perform the open circuit test of single phase transformer.
 Draw the circuit diagram.
 List the tools, equipment & materials required.
 Connect the equipment according to the diagram.
 Connect the low side of its rated supply voltage keeping high side open.
 Record the readings of the instruments.
 Calculate Io, Im, Iw, Ro and Xo.
 Draw no load vector diagram with data obtained.

Perform the short circuit test of a single phase transformer.
 Sketch the required circuit diagram.
 List tools, equipment & materials required.
 Connect the equipment according to the circuit diagram keeping high side to the source.
 Short circuit the low side by a low resistance wire.
 Energize the circuit by applying reduced voltage and increase the voltage until it takes full load of current.
 Record the instrument readings.
 Observe copper loss and calculate and find Re¢, Xe¢ & Ze¢.

Perform the polarity test of a single phase transformer.
 Draw the required circuit diagram.
 Collect tools, equipment & materials required.
 Connect the equipment according to the diagram.
 Connect the circuit to the source.
 Record the voltmeter readings.
 Determine whether it is additive or subtractive polarity.

Perform parallel operation of two single phase transformers.
 Draw the circuit diagram.
 Collect tools, equipment & materials required.
 Connect the equipment according to the circuit diagram with proper polarity.
 Energize the circuit and connect the load to the secondary.
 Record the power shared by each transformer.

Identify and rectify the troubles of a single phase transformer.
 Select a single phase transformer.
 Collect the tools and equipment required.
 Take a test lamp or an AVO meter.
 Perform continuity test, earth test and insulation test employing test lamp and AVO meter.
 Identify the troubles and suggest remedial measures.

Perform transformer banking.
 Collect the tools, equipment and materials required.
 Draw the circuit diagram of YY, YD, DD and DY banking respectively.
 Connect the equipment according to the diagram separately.
 Record the meter readings for each case separately.
 Calculate the voltage ratio in each case.

Perform the operation of autotransformer and determining its transformation ratio.
 Sketch the circuit diagram.
 Collect tools, equipment & materials required.
 Connect the equipment according to the circuit diagram.
 Energize the circuit and tabulate the meter readings.
 Calculate transformation ratio, conducted power & transformed power.

Perform the identification of the parts of a three phase induction motor.
 Select a 3phase induction motor.
 Collect different tools required for the experiment.
 List different parts of a 3phase induction motor.
 Dismantle the parts of the motor.
 Identify different parts and make sketch of each part. .
 Assemble the dismantled parts.

Start a 3phase induction motor by manual stardelta starter.
 Take a 3phase squirrel cage induction motor.
 Collect the equipment & tools required.
 Draw the working diagram to perform the experiment.
 Connect the starter with the motor as per diagram.
 Start the motor with the starter: first in star and then in delta position.
 Measure the speed of the motor with tachometer.
 Calculate slip of the motor.

Start a 3phase induction motor by automatic stardelta starter.
 Take a 3phase squirrel cage induction motor.
 Collect the equipment & tools required.
 Draw the working diagram to perform the experiment.
 Connect the starter with the motor as per diagram.
 Push the start button to start the motor automatically first in star and then in delta position.
 Measure the speed of the motor with tachometer.
 Calculate slip of the motor.
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