When engineers discuss magnetic component efficiency, they often focus on winding resistance and copper losses.

However, magnetic cores also generate losses.

In many high-frequency designs, core losses become one of the dominant factors affecting efficiency and temperature rise.

Understanding how core losses are generated and estimated is essential when designing inductors, transformers, flyback converters, and other magnetic components.

This guide explains the primary sources of core loss and the methods engineers use to evaluate them.

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What Are Core Losses?

Core losses are energy dissipated within the magnetic material itself.

Unlike copper losses, which occur in the winding conductors, core losses occur inside the magnetic core.

These losses appear as heat and reduce overall efficiency.

Core losses increase with:

• Frequency
• Flux density
• Temperature
• Material properties

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The Two Primary Loss Mechanisms

Most core losses consist of:

Hysteresis Loss

Eddy Current Loss

Both occur simultaneously but arise from different physical mechanisms.

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Hysteresis Loss

Magnetic materials contain microscopic magnetic domains.

As the magnetic field changes direction, these domains rotate and realign.

This process requires energy.

The energy lost during repeated magnetization cycles is called hysteresis loss.

Generally:

• Higher frequency increases hysteresis loss.
• Higher flux density increases hysteresis loss.

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Eddy Current Loss

Changing magnetic fields induce circulating currents inside conductive materials.

These currents are called eddy currents.

Eddy currents create:

• Resistive heating
• Additional losses
• Reduced efficiency

Modern ferrite materials are designed to minimize eddy current losses.

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Why Frequency Matters

Frequency is often the largest contributor to increasing core losses.

As switching frequency increases:

• Magnetic domains switch more frequently.
• Eddy current activity increases.
• Core heating increases.

👉 Related Guide: How Switching Frequency Affects Magnetics

This is one reason high-frequency designs require careful material selection.

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Why Flux Density Matters

Flux density has a dramatic effect on core losses.

As flux density increases:

• Hysteresis losses increase.
• Eddy current losses increase.
• Temperature rise increases.

Engineers often reduce flux density to improve efficiency.

👉 Related Guide: Understanding Magnetic Saturation

Operating near saturation generally increases losses significantly.

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The Steinmetz Equation

Many engineers estimate core loss using the Steinmetz equation.

$P_v=kf^{a}B^{b}$Pv​=kfaBb

Where:

• Pv = Core loss density
• k = Material constant
• f = Frequency
• B = Flux density
• a,b = Material-specific coefficients

Manufacturers typically provide these coefficients.

This equation provides a practical method for estimating magnetic losses.

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Core Material Selection

Different materials exhibit very different loss characteristics.

Common materials include:

• Ferrite
• Powdered Iron
• Amorphous
• Nanocrystalline

👉 Related Guide: How to Choose the Right Core Material

Selecting the proper material often has a larger impact than changing core size.

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Core Losses and Temperature Rise

Core losses appear as heat.

Higher losses produce:

• Higher temperatures
• Reduced efficiency
• Increased thermal stress

👉 Related Guide: How to Reduce Inductor Temperature Rise

Thermal evaluation should always accompany core loss analysis.

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Estimate Losses

Use the loss estimator below to explore magnetic loss tradeoffs.

[solidmag_loss_estimator]

This tool can help visualize how design choices influence efficiency and thermal performance.

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Core Losses vs Copper Losses

Many designs are dominated by one type of loss.

At lower frequencies:

• Copper losses often dominate.

At higher frequencies:

• Core losses often dominate.

Successful magnetic design requires balancing both.

👉 Related Guide: Inductor Efficiency Explained

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Reducing Core Losses

Engineers commonly reduce core losses by:

• Lowering flux density
• Selecting lower-loss materials
• Reducing switching frequency
• Increasing core size
• Improving thermal management

Every improvement involves tradeoffs.

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Practical Design Guidelines

When evaluating core losses:

✔ Check material data sheets.

✔ Verify operating frequency.

✔ Verify flux density.

✔ Evaluate thermal rise.

✔ Compare multiple materials.

✔ Consider efficiency targets.

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Quick Design Evaluation

Before committing to a final design, engineers often compare multiple candidate magnetic structures.

[solidmag_quick_estimator]

This helps identify promising designs before detailed optimization begins.

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Conclusion

Core losses are one of the most important factors affecting magnetic component efficiency.

Understanding hysteresis loss, eddy current loss, frequency effects, and material behavior allows engineers to create cooler, more efficient, and more reliable inductors and transformers.

Successful magnetic designs balance core losses with copper losses, thermal performance, manufacturability, and cost.

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Need Help Optimizing Magnetic Designs?

The SolidMagnetics platform helps engineers evaluate:

• Core losses
• Saturation margin
• Thermal performance
• Core materials
• Manufacturability

while automatically generating CAD models, engineering drawings, BOMs, and production-ready outputs.