AC Generator: Conversion of Mechanical to Electrical Energy

Introduction

• AC Generator: Device converting mechanical energy into electrical energy.
• Armature: Main metal part where electricity is generated.

Components and Operation

• Armature Rotation: Occurs between two magnets.
  • Rotational methods:
    • Pressurized steam (power plant)
    • Water flow (dam)
    • Air flow (wind turbine)
• Slip Rings:
  • Made of metal, connected to the armature.
  • Rotate with the armature.
• Brushes:
  • Made of carbon, contact slip rings to provide electron flow.
• Galvanometer: Measures magnitude and direction of current.

Generation of Electric Current

• Magnetic Flux: Total magnetic field passing through a surface.
• Current Formation:
  • Arises from changes in magnetic flux, not the flux itself.
  • Formula: Change in flux calculated by:
    • Angle between area vector and magnetic field impacts flux change.
  • Zero Flux Change: Occurs when armature is parallel to magnets, no current is generated.

Cycle and Current Direction

• Cycle Stages:
  • Quarter Cycle: Max change in flux, current peaks.
  • Half Cycle: Flux change zero, current zero.
  • Three-Quarter Cycle: Max change in flux again, current peaks.
  • Full Cycle: Flux change zero again, completes cycle.
• Current Direction:
  • Fleming's Right Hand Rule:
    • First Half Cycle: Current direction inward.
    • Second Half Cycle: Current direction outward.
  • Current Change: Every half cycle, direction changes.

AC vs. DC

• Alternating Current (AC): Current changes direction every half cycle.
• Direct Current (DC): Uses split ring to maintain current direction.

Frequency and Historical Context

• AC Frequency:
  • United States: 60 Hz, current changes 60 times/second.
  • Europe: 50 Hz, current changes 50 times/second.
• 19th-Century Choices:
  • Efficient steam turbine speeds:
    • Europe: 3000 RPM, 50 Hz.
    • US: 3600 RPM, 60 Hz.