EMF Induction in Rotating Loop

Voltage Induction in a Rotating Loop

• A voltage is induced in a wire loop when the rotor of a machine is rotated.

Magnetic Field and Rotor Surface

• The magnetic field is constant and perpendicular to the rotor surface everywhere under the pole faces.
• The magnetic field rapidly falls to zero beyond the edges of the poles.

Voltage in Each Segment of the Loop

• Segment ab:
  • Velocity of the wire is tangential to the path of rotation.
  • Magnetic field B points out perpendicular to the rotor surface.
  • v × B points into the page, resulting in a positive voltage.
  • e ba = (v × B)l, where v is velocity, B is magnetic field, and l is length.
• Segment bc:
  • v × B is either into or out of the page, while length l is in the plane of the page.
  • v × B is perpendicular to l, resulting in zero voltage.
  • e cb = 0
• Segment cd:
  • Velocity of the wire is tangential to the path of rotation.
  • Magnetic field B points in perpendicular to the rotor surface.
  • v × B points out of the page, resulting in a voltage.
  • e dc = (v × B)l, where v is velocity, B is magnetic field, and l is length.

Total Voltage

• The total voltage etot is the sum of the voltages in each segment of the loop.