Electrical Machine-I Sessional (EEE2106)
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Questions and Answers

What is the rated power of the single-phase induction motor?

  • 1 kW (correct)
  • 0.5 kW
  • 2 kW
  • 3 kW

    • Which of the following describes the armature resistance of the 2 kW DC machine?

  • 2.00 Ω
  • 1.68 Ω (correct)
  • 2.50 Ω
  • 1.25 Ω

    • What is the service factor of the 4 1/2 kW DC generator/motor?

  • 1.5
  • 1.0
  • 1.15 (correct)
  • 1.75

    • How many phases does the 3-phase induction motor operate on?

    <p>Three-phase</p> Signup and view all the answers

    What is the full-load current of the synchronous generator rated at 4 KVA?

    <p>19.2 A</p> Signup and view all the answers

    What is the field current for the 4 1/2 kW DC machine?

    <p>1.0 A</p> Signup and view all the answers

    What is the total voltage rated for the synchronous motor?

    <p>220 V</p> Signup and view all the answers

    What occurs when coils are connected in subtractive polarity?

    <p>The voltmeter reading will be zero.</p> Signup and view all the answers

    What is the turns ratio for the provided data where the primary voltage is 100V and the secondary voltage is 50V?

    <p>0.5</p> Signup and view all the answers

    What is the formula to determine primary resistance R1?

    <p>R1 = V1 / I1</p> Signup and view all the answers

    If the secondary voltage V2 is 300V with additive polarity, what can be concluded about terminals X1 and X3?

    <p>They have the same polarity.</p> Signup and view all the answers

    In the provided data table, what is the equivalent resistance referred to the primary side when the secondary side resistance is R2?

    <p>Equivalent resistance = R2 / (N2/N1)</p> Signup and view all the answers

    Which resistance value corresponds to the highest voltage input of 200V in the table?

    <p>244.1</p> Signup and view all the answers

    What impact does increasing the primary voltage have on the secondary current, assuming a constant turns ratio?

    <p>It decreases the secondary current.</p> Signup and view all the answers

    What is the relationship between primary current I1 and secondary current I2 based on the data provided?

    <p>I1 is inversely proportional to I2.</p> Signup and view all the answers

    What is the formula for calculating the efficiency of a system?

    <p>Efficiency = (Output - Losses) × 100 / Input</p> Signup and view all the answers

    What does a high percentage of regulation in a transformer indicate?

    <p>Significant voltage change with load variations</p> Signup and view all the answers

    When conducting a short circuit test, what does R01 and X01 refer to?

    <p>Resistance and reactance on the high tension side</p> Signup and view all the answers

    What is indicated by the efficiency of 90% in the calculation provided?

    <p>The losses account for 10% of the input power</p> Signup and view all the answers

    Which module is NOT listed as part of the apparatus for the experiment?

    <p>AC Power Meter</p> Signup and view all the answers

    What is the effect of internal resistance and reactance on transformer regulation?

    <p>They cause a decrease in voltage at the load with an increase in load</p> Signup and view all the answers

    Which of the following describes the term 'load' in the context of a transformer regulation experiment?

    <p>The demand for power that the transformer must meet</p> Signup and view all the answers

    What do the variable knobs K3 and K4 control in the experiment setup?

    <p>The input voltage levels</p> Signup and view all the answers

    What is the first step to start the procedure for the experiment?

    <p>Keep all the Loads at OFF position.</p> Signup and view all the answers

    Which of the following is NOT a condition for two transformers to operate in parallel?

    <p>The relative polarities on the primary and secondary sides should be opposite.</p> Signup and view all the answers

    What should be noted when all Loads are turned ON?

    <p>The readings on the AC Voltmeter, Ammeter, and Wattmeter Module.</p> Signup and view all the answers

    What is representing the load in an R-C load scenario?

    <p>Combination of resistive and capacitive components.</p> Signup and view all the answers

    Which equipment is used to determine the R and X values on the secondary side?

    <p>R-L-C meter.</p> Signup and view all the answers

    What does the term 'regulation' refer to in the context of transformer operation?

    <p>The change in voltage from no load to full load.</p> Signup and view all the answers

    What is indicated if the mA deflects in the positive direction during the relative polarity test?

    <p>H1 and X1 have the same mode of winding.</p> Signup and view all the answers

    What should be done after completing the readings with resistive load?

    <p>Draw vector diagrams and calculate regulation.</p> Signup and view all the answers

    What happens to the phase voltage when an induction motor is started using a star-delta starter?

    <p>It is reduced to 0.58 of normal voltage.</p> Signup and view all the answers

    Why is the star-delta starting method unsuitable for motors at voltages exceeding 3000 V?

    <p>Excessive number of stator turns are needed for delta running.</p> Signup and view all the answers

    What is the starting torque behavior of an induction motor when using the star-delta starter?

    <p>The starting torque is one-third of the short-circuit value.</p> Signup and view all the answers

    Under which condition is the star-delta starting method effective?

    <p>When the application is light loaded during the start.</p> Signup and view all the answers

    What happens after the induction motor reaches its operational speed during star-delta starting?

    <p>It is switched to delta configuration.</p> Signup and view all the answers

    What is one method of connecting three transformers for 3-phase circuits?

    <p>Δ-Y connection</p> Signup and view all the answers

    In a three-phase transformer bank, which connection type allows for a phase shift of 30 degrees?

    <p>Y-Δ connection</p> Signup and view all the answers

    Which component measures the current in the AC circuit during the experiment?

    <p>AC Ammeter Module</p> Signup and view all the answers

    What type of curve is created by plotting torque against slip for an induction motor?

    <p>Rectangular hyperbola</p> Signup and view all the answers

    Which of the following statements is true regarding the efficiency determination for each transformer combination?

    <p>Efficiency is determined after measuring voltmeter and ammeter readings.</p> Signup and view all the answers

    What happens to the running torque as the slip increases in an induction motor?

    <p>Running torque increases and reaches maximum at breakdown torque.</p> Signup and view all the answers

    Which equipment is NOT mentioned as part of the experiment setup for testing transformer connections?

    <p>DC Voltmeter</p> Signup and view all the answers

    What should be done before applying voltage to the transformer setup?

    <p>Connections should be verified by the lab teacher.</p> Signup and view all the answers

    Study Notes

    Electrical Machine-I Sessional (EEE2106)

    • Experiment 1: Polarity test and voltage/current relationship between transformer primary and secondary.

      • Transformer theory: A device that transfers electrical energy from one circuit to another without changing frequency.

      • Types: Step-up (primary voltage > secondary voltage) and step-down (opposite).

      • Polarity: Determined through testing, additive or subtractive.

      • Voltage and current relationship: E₁/N₁ = E₂/N₂ and I₁/N₂ = I₂/N₁ (where E and I are voltage and current, and N are turns).

    • Experiment 2: Open-circuit and short-circuit tests of a single-phase transformer.

      • Purpose: To determine the transformer's core loss and copper loss.

      • Core loss (iron loss): Measured by open-circuit test with rated voltage but no load to isolate core loss.

      • Copper loss (constant loss): Measured by short-circuit test with reduced voltage.

      • Efficiency calculation: Output power/input power.

    • Experiment 3: Transformer regulation under different power factors.

      • Purpose: To determine voltage change with varying load conditions (different power factors).

      • Regulation calculation: % Regulation = (Vnl - Vfl) / Vfl * 100 (where Vnl is no-load voltage, Vfl is full-load voltage).

    • Experiment 4: Parallel operation of transformers.

      • Purpose: Connecting two or more transformers to share the load capacity exceeding the capacity of a single transformer efficiently.

      • Conditions: Primary and secondary voltages must be identical, and polarities must be the same.

    • Experiment 5: Construction of three-phase transformers.

      • Using three single-phase transformers to build a three-phase transformer.

      • Relation between line and phase voltages/currents is explained.

      • Concepts of balanced/unbalanced loads are explored.

    • Experiment 6: Efficiency of three-phase transformers.

      • Determines the ratio of output power to input power.

    • Experiment 7: Speed-torque characteristic curve of a three-phase induction motor.

      • Purpose: To study the motor's performance curve for various operating conditions.

      • The graphical correlation of motor speed versus torque is noted.

    • Experiment 8: Blocked Rotor and No-load tests on three-phase induction motors.

    • Experiment 9: Study of a single-phase induction motor.

      • Self-starting mechanism through the usage of auxiliary windings in the stator windings.

    • Experiment 10: Circuit parameter measurement & efficiency calculation of single-phase induction motors.

    • Experiment 11: Capacitor value determination for maximum starting torque in split-phase induction motors.

      • Factors explored by varying capacitor value in the auxiliary winding.

    • Experiment 12: Starting an induction motor using a star-delta starter.

      • Purpose: A method for reducing starting current and preventing potential damage to the motor.

    Other topics

    • DC Machines:

      • DC generators convert mechanical energy into electrical energy.
      • DC motors convert electrical energy into mechanical energy.

    • Synchronous Machines:

      • Constant-speed machines, used in power generation.

    • Induction Motors:

      • AC motors used for various applications, have adjustable speeds

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    Related Documents

    EEE Machines Lab Manual PDF

    Description

    This quiz focuses on key concepts and experiments related to transformers, including polarity tests and efficiency calculations. It covers the electrical characteristics of both step-up and step-down transformers, as well as open-circuit and short-circuit tests to determine losses. Test your understanding of these essential electrical engineering principles.

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