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Electrical Engineering
Electrical Machines I- BE03009021


Syllabus GTU PYQ Papers  IMP Question Bank/Paper Solution  Study Material: Assignment/Video Lectures


Syllabus Detail

*AY-Academic Year*

New Syllabus (AY-2024-25)

Old Syllabus (AY-2018-19)

What’s Changed?

GTU Winter Exam Previous Year Question Papers

Winter-2025

Winter-2022 TO 2025 (3140913)

GTU Summer Exam Previous Year Question Papers

Summer-2022 TO 2026 (3140913)

Summer-2026 

Important Question Bank 

 Everything you need to get started with exam preparation.


Compiled GTU Question Papers: S22 to W25 (Question Bank)

Compiled GTU Question Papers: S22 to W25 (Answer Bank)

GTU Winter Exam Solved Papers


Winter-2025

Winter-2024

GTU Summer Exam Solved Papers

Summer-2025

Summer-2024

Study Material/Assignment


Assignments ( Coming Soon )

Study Material: Video Lessons & Tutorials


The video library is currently being finalized and will go live shortly.

Subtopic Key Concepts Video Focus Areas
1.1 Review of Single Phase Transformer Basic construction: Core, windings (Primary/Secondary), Laminated core (to reduce eddy currents). Principle of operation: Mutual induction. EMF equation: E = 4.44 f φ_m N.
1.2 Equivalent Circuit & Phasor Diagrams Exact equivalent circuit. Approximate equivalent circuit (referred to primary/secondary). Phasor diagrams at leading, lagging, and unity power factor.
1.3 Losses & Efficiency Core (Iron) losses: Hysteresis loss, Eddy current loss. Copper losses (I²R). Separation of no-load losses (hysteresis and eddy current). Condition for maximum efficiency: Copper loss = Iron loss.
1.4 Determination of Equivalent Circuit Parameters Open Circuit (O.C.) Test: Determines core losses and shunt branch parameters (R₀, X₀). Short Circuit (S.C.) Test: Determines copper losses and series branch parameters (R_eq, X_eq).
1.5 Efficiency & Voltage Regulation Calculating efficiency at any load and power factor. Voltage regulation: % Regulation = (E₂ - V₂)/V₂ × 100. Direct load test. Sumpner's test (Back-to-Back test) for efficiency and temperature rise.
1.6 Auto Transformer Construction: Single winding with tapping. Saving of copper: (V₁ - V₂)/V₁ × 100%. Applications: Voltage regulators, starters for induction motors.
1.7 Parallel Operation of Transformers Conditions for parallel operation: Same voltage ratio, same percentage impedance, same polarity, same phase sequence (for 3-phase). Load sharing under different operating conditions.
1.8 Polarity Test Polarity test: Additive and subtractive polarity. Importance in parallel operation and instrument transformer connections.
Subtopic Key Concepts Video Focus Areas
2.1 Construction & Types Construction: Core type, Shell type. Types of connections: Star (Y), Delta (Δ), Zig-zag. Comparative features (voltage, current, insulation).
2.2 Vector Groups Vector groups (e.g., Yy0, Yd11, Dyn11). Importance in parallel operation. Terminal marking and nomenclature (IS 2026).
2.3 Parallel Operation of Three Phase Transformers Conditions for parallel operation: Same voltage ratio, same percentage impedance, same vector group. Load sharing.
2.4 Magnetizing Current & Harmonics Magnetizing current: Non-sinusoidal (contains harmonics). Effect of connection type on harmonics (Delta connection provides a path for third harmonics).
2.5 Scott Connection Scott connection: Converting three-phase to two-phase (or vice versa).
2.6 Tap Changing & Three-Winding Transformers No-load tap changing (off-circuit). On-load tap changing (OLTC). Three-winding transformers (primary, secondary, tertiary).
2.7 Cooling of Transformers Methods of cooling: ONAN (Oil Natural Air Natural), ONAF (Oil Natural Air Forced), OFAF (Oil Forced Air Forced), OFWF (Oil Forced Water Forced).
2.8 Short Circuit Forces & Mechanical Stresses Forces due to short circuit currents: Radial forces, Axial forces. Mechanical stresses on windings.
2.9 Protective & Safety Devices Buchholz relay (gas-operated relay), Pressure relief valve, Oil level indicator, Temperature indicator, Surge arresters.
2.1 Applications Application in various electrical systems: Transmission, Distribution, Instrumentation (CT, PT), Special transformers (Earthing transformer, Furnace transformer).
Subtopic Key Concepts Video Focus Areas
3.1 Construction & Classification Construction: Stator (core + windings), Rotor (Squirrel cage or Wound rotor). Classification: Squirrel cage, Slip-ring (wound rotor).
3.2 Principle of Operation & Rotating Magnetic Field Production of rotating magnetic field (RMF) by three-phase currents. Speed of RMF: N_s = 120f/P. Slip: s = (N_s - N_r)/N_s.
3.3 Torque Equations Starting torque, Full load torque, Maximum torque. Condition for maximum torque (R₂ = sX₂). Condition for maximum output.
3.4 Torque-Slip Characteristics Torque-slip curve (T vs. s). Stable and unstable regions. Effect of parameter variation on torque-speed characteristics: Rotor resistance, Stator voltage, Frequency, Stator resistance.
3.5 Phasor Diagram & Equivalent Circuit Equivalent circuit (referred to stator). Phasor diagram. Losses and efficiency.
3.6 Tests on Induction Motors No load test: Determines core losses and magnetizing reactance. Blocked rotor test: Determines leakage reactances and rotor resistance.
3.7 Circle Diagram Circle diagram: Predetermination of performance under different operating conditions.
3.8 Methods of Starting Direct On Line (DOL) starting. Star-Delta starting. Auto-transformer starting. Rotor resistance starting (for wound rotor motors). Soft starters (solid state).
3.9 Speed Control Methods Speed control: Voltage control, Frequency control (V/f control), Pole changing, Rotor resistance control, Slip power recovery (Kramer, Scherbius).
3.10 Harmonics, Crawling & Cogging Effect of harmonics on torque-slip characteristics. Crawling: Motor runs at a sub-synchronous speed. Cogging: Rotor refuses to start.
3.11 Energy Efficient Motors Energy Efficient three-phase induction motors: Features (better materials, improved design).
3.12 Induction Generator Principle of operation (Rotor speed > Synchronous speed). Equivalent circuit and application (wind turbines, regenerative braking).
Subtopic Key Concepts Video Focus Areas
4.1 Double Field Revolving Theory Double field revolving theory: A pulsating field is equivalent to two rotating fields (forward and backward) of half the amplitude.
4.2 Equivalent Circuit of Single-Phase Induction Motor Equivalent circuit (forward and backward fields). Starting and running performance.
4.3 Types of Single-Phase Motors Types: Split phase, Resistance start, Capacitor start, Capacitor start & run, Shaded pole, Universal motor, Repulsion motor.
4.4 Split Phase & Resistance Start Motors Split phase: Auxiliary winding (high resistance, low reactance) and Main winding. Resistance start: Resistor in series with auxiliary winding.
4.5 Capacitor Start & Capacitor Start-Run Motors Capacitor start: Capacitor in series with auxiliary winding (large phase shift). Capacitor start-run: Capacitor permanently connected.
4.6 Shaded Pole Motor Shaded pole motor: Auxiliary winding is a shading coil. Very low starting torque.
4.7 Universal Motor Universal motor: Series motor that can run on AC or DC.
4.8 Repulsion Motor Repulsion motor: Stator has a single winding, rotor has a commutator and brushes.
4.9 Applications Applications of various single-phase motors (domestic, industrial).

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