A single phase transformer has 1000 turns on the primary and 200 turns on the secondary. The no load current is 3A at a power factor of 0.2 lag and the secondary current is 280A at a power factor of 0.8 lag. Neglect R_{2 }and X_{2} calculate (1) Magnetizing component and loss component of no load current. (2) primary current (3) input power factor .Draw phasor diagram showing all the currents.

Concept: Construction of Single Phase Transformer

Find the node voltages 𝑽_{𝟏},𝑽_{𝟐 }𝒂𝒏𝒅 𝑽_{𝟑} and current through 0.5Ω

Concept: Three Phase Voltage Genration

Find the RMS value of the waveform given below:-

Concept: RMS and Average Value

A balanced 3 phase star connected load consists of three coils each consisting of R=6Ω and 𝑿𝑳= 8Ω . Determine the line current , power factor when the load is connected across 400V, 50Hz, supply

Concept: Three Phase Current Generation

Describe the basic principle of operation of a single phase transformer and derive the emf equation.

Concept: Working Principle of Single Phase Transformer

Briefly explain the classification of DC machine.

Concept: Construction and Classification of Dc Machines

Using the mesh analysis find the mesh current in the direction shown and also find the voltage across A and B terminals.

Concept: Mesh Analysis

A resistance and a capacitor connected in series across a 250V supply draws 5A at 50Hz. When frequency is increased to 60Hz, it draws 5.8A. Find the values of R & C. Also find active power and power factor in both cases.

Concept: AC Through Resistance

Draw the phasor diagram of a single phase transformer when it is loaded with a lagging power factor load.

Concept: phasor diagrams of Single Phase Transformer

In an R-L-C parallel circuit the current through the resistor, inductor(pure), and capacitor (pure) are 20A, 15A and 40A respectively. What is the current from the supply ?draw the phasor diagram.

Concept: R-L, R-C and R-LC parallel circuits

The OC and SC test data are given below for a single phase, 5KVA, 200V/400V, 50Hz transformer

OC test from LV side | 200V | 1.25A | 150w |

SC test from HV side | 20V | 12.5A | 175w |

Determine the following :-

1) Draw the equivalent circuit of the transformer referred to LV side.

2) At what load or KVA the transformer is to be operated for maximum efficiency?

3) Calculate the value of maximum efficiency.

4) Regulation of the transformer at full load 0.8power factor lagging.

Concept: OC and SC Test

Find current I_{X} using Superposition theorem

Concept: Superposition Theorem

Prove that the average power taking by a pure capacitor fed with a sinusoidal ac supply in a circuit is zero.

Concept: Power and Power Factor

State Norton’s theorem and draw the Norton’s equivalent circuit.

Concept: Norton’S Theorem

Derive the formula for resonant frequency of the circuit with a pure capacitor in parallel with a coil having resistance and inductance. Find the expression for dynamic resistance of this parallel resonant circuit.

Concept: Series and Parallel Resonance

Determine the value of R for maximum power transfer and find the value of maximum transfer.

Concept: Maximum Power Transfer Theorem