Eddy currents are associated with alternating current (AC).
Understanding Eddy Currents
Eddy currents are loops of electrical current induced within a conductor by a changing magnetic field. This changing magnetic field is typically produced by alternating current.
Why Eddy Currents Occur with AC
- Faraday's Law of Induction: This law states that a changing magnetic field induces a voltage (electromotive force) in any conductor within that field.
- AC Creates a Changing Magnetic Field: Alternating current, by its nature, constantly changes in magnitude and direction. This continuous change produces a continuously changing magnetic field around the conductor carrying the AC.
- Induced Currents: This changing magnetic field then induces circulating currents (eddy currents) within the conductor itself.
Consequences of Eddy Currents
The flow of eddy currents within a conductor leads to several effects:
- Energy Loss: Eddy currents dissipate energy as heat due to the electrical resistance of the conductor. This is an undesirable energy loss in many applications.
- Magnetic Field Opposition: Eddy currents create their own magnetic field, which opposes the original changing magnetic field.
Minimizing Eddy Current Losses
Because eddy currents cause energy loss in alternating current (AC) applications such as inductors, transformers, electric motors, and generators, specific designs are implemented to minimize their effects. These designs typically include:
- Laminated Cores: Instead of using a solid core in transformers and inductors, the core is made up of thin, insulated laminations. This increases the resistance to eddy current flow, reducing their magnitude.
- Ferrite Cores: Ferrites are ceramic materials with high magnetic permeability and high electrical resistivity. Their high resistivity minimizes eddy current losses, especially at high frequencies.
Example Applications Where Eddy Currents are Important
- Transformers: Eddy currents in the transformer core cause energy loss and heat generation.
- Electric Motors and Generators: Eddy currents in the rotor and stator can reduce efficiency.
- Induction Heating: Eddy currents are intentionally used to heat conductive materials in applications like induction furnaces.
- Eddy Current Brakes: Used in trains and roller coasters, where eddy currents provide braking force.
