In electrical steel, used in transformers, motors, and other magnetic components, core loss represents the energy wasted as heat due to two main mechanisms: hysteresis loss and eddy current loss. Minimizing these losses is crucial for efficient operation.
1. Hysteresis Loss:
Imagine rolling a marble along a bumpy track. It takes more energy to overcome the bumps and keep the marble moving than on a smooth track. Similarly, when we magnetize and demagnetize electrical steel repeatedly, the magnetic domains within the material “stick” slightly, making it harder to reverse their direction. This energy lost in overcoming this internal resistance is hysteresis loss. It depends on the frequency and peak value of the magnetic field applied.
2. Eddy Current Loss:
When a changing magnetic field interacts with any conductor, it induces tiny circulating currents called eddy currents. These currents dissipate energy as heat within the conductor. In electrical steel, these currents flow within the metal itself. To minimize eddy currents, electrical steel is often made of thin, insulated laminations stacked together. Thinner laminations increase the resistance of the paths for eddy currents, reducing their flow and the associated losses.
Average Loss Amount:
The average core loss in electrical steel depends on several factors, including:
- Grade of steel: Different grades of steel have varying grain sizes and compositions, impacting magnetic properties and loss characteristics.
- Frequency of the magnetic field: Higher frequencies lead to more rapid changes in the magnetic field, increasing both hysteresis and eddy current losses.
- Peak magnetic flux density: Stronger magnetic fields exert greater force on the magnetic domains, causing higher hysteresis loss.
- Thickness of laminations: Thinner laminations reduce eddy current losses.
Therefore, it’s difficult to give a single “average” loss amount. For example, a typical loss value for non-grain-oriented steel at 50 Hz and 1.5 Tesla might be around 1.5 W/kg, while grain-oriented steel with optimized laminations at the same frequency and flux density could be as low as 0.4 W/kg.
Minimizing Losses:
Engineers seek to minimize core losses in electrical steel components by:
- Choosing the appropriate steel grade for the application and frequency.
- Using thin, insulated laminations.
- Optimizing the design of the magnetic circuit to minimize the required peak flux density.
- Employing advanced materials and technologies that further reduce losses.
By understanding and mitigating core losses, we can create more efficient and energy-saving electrical equipment.