AC Voltage generation

AC Voltage Generation

  • Sinusoidal waveform represents one cycle of alternating voltage/current.

  • Electrical alternator rotates through 360°:

    • Output voltage rises from 0 V to peak, falls back to 0 V, and repeats in opposite polarity.

Sinusoidal Waveform

  • Key characteristics include:

    • Smooth continuous wave.

    • Important for understanding AC voltage characteristics.

Generation of EMF (Electromotive Force)

  • Fleming's Right Hand Rule:

    • Thumb: Direction of motion.

    • First Finger: Polarity of the magnetic field.

    • Second Finger: Polarity of conventional current.

  • Remember: Magnetic field direction is from North (N) to South (S).

Practical Use of Fleming’s Right Hand Rule

  • Example:

    • Assume conductor moves upwards.

    • Magnetic field: North to South.

    • Current flow directed towards the observer.

Single-Loop AC Generator

  • Frequency Calculation:

    • Formula: f = N × P

      • f = frequency

      • P = pole pairs

      • N = speed of rotation (in revs/second).

Induced EMF Calculation in a Single-Phase AC Generator

  • Formula: e = E sinΦ

    • φ = phase angle for induced emf calculation.

    • E = peak value of the induced emf.

    • Use sine function for angles between 0° and 360°.

Phase Angle

  • Definition:

    • Phase angle (Φ) indicates the angle of shift in degrees/radians along the horizontal axis.

    • Full phase is 360 degrees.

Calculating Induced EMF for Different Phase Angles

  • For angles greater than 90°:

    • Use specific sine rules based on the range of the angle.

    • Example rules:

      • 90° to 180°: sinΦ = sin(180 - Φ)

      • 180° to 270°: sinΦ = -sin(360 - Φ)

      • 270° to 360°: sinΦ = -sin(Φ - 180)

  • Worked example approach:

    1. Calculate sinΦ for desired angle.

    2. Use the formula e = E sinΦ with the calculated value.

Summary

  • Sinusoidal waveform represents AC voltage/current cycle.

  • Fleming's Right Hand Rule helps determine current flow direction based on motion and magnetic field.

  • EMF in single-phase AC generator calculated using e = E sinΦ, accounting for phase angle.

  • Different rules apply for calculating sine values based on angle ranges.