Test Methods To Quantify Core Loss At 100 KHz And Above For Amorphous Soft Magnetic Alloys In High-Frequency Power Electronics

The evolution of power electronics has been marked by a continuous pursuit of higher efficiency, smaller form factors, and increased power density. Since the 1970s, magnetic components have been critical elements in power conversion systems, with core losses representing a significant portion of overall energy losses. The emergence of wide bandgap semiconductors like SiC and GaN in the early 2000s has enabled switching frequencies to exceed 100 kHz, dramatically reducing the size of magnetic components but introducing new challenges in core loss characterization.

Amorphous soft magnetic alloys, first developed commercially in the 1980s, have gained significant attention for high-frequency applications due to their unique microstructure that minimizes eddy current losses. However, accurately quantifying core losses at frequencies above 100 kHz remains problematic due to limitations in conventional testing methodologies that were primarily designed for lower frequency ranges (typically below 20 kHz).

The traditional Steinmetz equation and its derivatives become increasingly inaccurate at higher frequencies, where non-sinusoidal waveforms and complex magnetization processes dominate. Industry standards such as IEC 60404 and IEEE 393 provide guidelines for core loss measurement, but these standards have not been fully adapted for the ultra-high frequency domain relevant to modern power electronics.

This technical research aims to comprehensively evaluate existing test methods for quantifying core losses in amorphous soft magnetic alloys at frequencies of 100 kHz and above, while identifying their limitations and potential improvements. The primary objective is to establish reliable, reproducible, and practical testing protocols that accurately characterize core losses under conditions representative of actual high-frequency power electronic applications.

Secondary objectives include developing mathematical models that can accurately predict core losses across various operating conditions, creating standardized testing procedures that can be widely adopted by the industry, and exploring the correlation between material microstructure and high-frequency magnetic performance in amorphous alloys.

The research will focus particularly on non-sinusoidal excitation conditions typical in switch-mode power supplies, wireless power transfer systems, and electric vehicle charging infrastructure, where accurate core loss prediction is essential for optimal design. By addressing these challenges, this research aims to accelerate the adoption of advanced magnetic materials in next-generation power electronics, contributing to improved energy efficiency and reduced environmental impact across multiple industries.

The global market for high-frequency magnetic materials, particularly amorphous soft magnetic alloys, is experiencing robust growth driven by the increasing demand for efficient power electronics across multiple industries. The market size for soft magnetic materials was valued at approximately $25 billion in 2022 and is projected to grow at a CAGR of 7.8% through 2030, with high-frequency applications representing the fastest-growing segment.

Power electronics applications operating at frequencies of 100 kHz and above are becoming increasingly prevalent in renewable energy systems, electric vehicles, data centers, and industrial automation. This shift toward higher frequencies is primarily motivated by the need for smaller, lighter, and more efficient power conversion systems. Amorphous soft magnetic alloys are particularly well-positioned to meet these demands due to their superior performance characteristics at high frequencies.

The electric vehicle (EV) sector represents one of the most significant market drivers, with onboard chargers and DC-DC converters increasingly operating at frequencies above 100 kHz to reduce size and weight while improving efficiency. The global EV market is expected to grow at a CAGR of 21% through 2030, creating substantial demand for high-performance magnetic materials that can operate efficiently at high frequencies.

Renewable energy systems, particularly solar inverters and wind power converters, constitute another major market segment. The transition to silicon carbide (SiC) and gallium nitride (GaN) power semiconductors in these applications is enabling switching frequencies well above 100 kHz, necessitating magnetic materials with minimal core losses at these frequencies.

The telecommunications and data center industries are also driving demand for high-frequency magnetic materials, with power supplies and server power management systems requiring increasingly compact and efficient designs. The global data center power market is growing at approximately 6.5% annually, with efficiency requirements becoming more stringent.

Industry surveys indicate that manufacturers of power electronics are prioritizing efficiency improvements, with over 70% of respondents identifying core loss reduction as a critical factor in their design considerations. This has created a strong market pull for both improved magnetic materials and more accurate testing methods to quantify core losses at high frequencies.

The market demand for standardized and reliable test methods for quantifying core losses at high frequencies is particularly acute, as existing testing protocols often show significant variations between different measurement techniques. This inconsistency creates challenges for design engineers when selecting materials and dimensioning components, highlighting the commercial value of improved testing methodologies.

The accurate measurement of core losses in amorphous soft magnetic alloys at frequencies above 100 kHz presents significant technical challenges that impede both research advancement and industrial application. Traditional measurement methods such as the Epstein frame and toroidal testing, which are standardized for lower frequencies (typically below 20 kHz), become increasingly unreliable as frequency increases due to skin and proximity effects, as well as parasitic impedances that distort readings.

One primary challenge is the separation of core losses from other system losses. At high frequencies, the measurement system's parasitic components—including lead inductance, capacitive coupling, and contact resistance—can contribute significantly to the total measured loss, sometimes exceeding the actual core loss. This makes it difficult to isolate and quantify the true material performance.

Temperature control represents another critical challenge. Amorphous alloys exhibit temperature-dependent magnetic properties, with core losses varying substantially across operating temperatures. During high-frequency testing, localized heating can occur rapidly, creating thermal gradients within the sample that lead to non-uniform magnetic performance and measurement inconsistencies.

The waveform integrity issue becomes particularly problematic above 100 kHz. Sinusoidal excitation waveforms tend to distort at high frequencies due to core nonlinearities and measurement circuit limitations. Since core loss is highly dependent on the excitation waveform shape, maintaining controlled test conditions becomes extremely difficult, leading to poor reproducibility between different test setups and laboratories.

Calibration standards for high-frequency measurements represent a significant gap in the industry. While low-frequency calibration materials and methods are well-established, reference materials and standardized procedures for frequencies above 100 kHz remain underdeveloped, creating uncertainty in measurement accuracy and hindering meaningful comparison between different research results.

The dynamic B-H loop measurement, crucial for understanding energy loss mechanisms, becomes increasingly challenging at high frequencies due to phase errors between measured voltage and current signals. Even minor phase discrepancies of less than one degree can lead to substantial errors in loss calculation, requiring extremely precise instrumentation and careful signal processing techniques.

Additionally, the physical sample preparation for high-frequency testing introduces variables that affect measurement consistency. Mechanical stress during sample handling, cutting, or mounting can alter the magnetic properties of amorphous alloys, which are particularly sensitive to stress conditions. This creates difficulties in establishing repeatable test protocols that yield consistent results across different laboratories and testing facilities.

The high-frequency core loss quantification market for amorphous soft magnetic alloys is in a growth phase, driven by increasing demand for efficient power electronics. The global market is expanding rapidly as industries seek energy-efficient solutions, with significant research activity across academic and industrial sectors. Leading companies like Metglas, Inc., TDK Corp., and Proterial Ltd. have established strong positions through specialized expertise in amorphous materials, while AMOGREENTECH and Advanced Technology & Materials Co. are emerging as innovative competitors. Research institutions including Harbin Institute of Technology and Zhejiang University are advancing testing methodologies. The technology is approaching maturity for lower frequencies but remains in development for applications above 100 kHz, creating opportunities for companies with advanced measurement capabilities and material science expertise.

The standardization of test methods for high-frequency core loss measurement represents a critical advancement in the field of power electronics, particularly for amorphous soft magnetic alloys operating at frequencies of 100 kHz and above. Several international organizations have been actively working to establish unified testing protocols that ensure consistency and reliability in core loss quantification.

IEEE Power Electronics Society has formed a dedicated working group (WG P2166) focused on standardizing test methods for magnetic materials at high frequencies. This initiative aims to address the significant variations in measurement techniques currently employed across the industry, which often lead to discrepancies in reported core loss values for identical materials.

The International Electrotechnical Commission (IEC) has also made substantial progress through its Technical Committee 51, which is developing standards specifically for measuring magnetic properties at frequencies exceeding 100 kHz. Their work includes defining precise measurement conditions, equipment specifications, and data processing methodologies to ensure reproducibility of results across different laboratories.

ASTM International's Committee A06 on Magnetic Properties has been revising existing standards to incorporate high-frequency testing protocols. Their approach emphasizes the unique challenges posed by amorphous alloys, including the need for specialized sample preparation techniques and consideration of skin effect phenomena at elevated frequencies.

Japan's Industrial Standards Committee (JISC) has pioneered several testing methodologies specifically designed for amorphous and nanocrystalline materials, contributing valuable insights to global standardization efforts. Their standards have gained recognition for addressing the temperature-dependent behavior of core losses at high frequencies.

The European Committee for Electrotechnical Standardization (CENELEC) has established a harmonization program to align European standards with international protocols, focusing particularly on calorimetric measurement techniques that offer advantages for high-frequency loss determination in amorphous materials.

Collaborative round-robin testing programs involving multiple research institutions and industrial partners have been instrumental in validating proposed standards. These programs have highlighted the importance of accounting for measurement uncertainties and establishing clear calibration procedures for test equipment operating at frequencies above 100 kHz.

Recent standardization efforts have increasingly incorporated digital twin modeling approaches, allowing for virtual validation of physical test methods and expanding the applicability of standards across diverse material compositions and core geometries used in modern power electronic applications.

Thermal management is a critical consideration in high-frequency testing of amorphous soft magnetic alloys, particularly when operating at frequencies of 100 kHz and above. As testing frequencies increase, the heat generated during measurement can significantly impact the accuracy of core loss quantification and potentially alter the magnetic properties of the material under test.

The primary challenge in thermal management stems from the rapid heat generation in the core material during high-frequency excitation. Amorphous soft magnetic alloys, while exhibiting superior performance at high frequencies compared to traditional silicon steel, still generate considerable heat due to hysteresis and eddy current losses. This heat generation increases exponentially with frequency, making thermal considerations paramount above 100 kHz.

Temperature rise during testing can introduce several measurement errors. First, the magnetic properties of amorphous alloys are temperature-dependent, with permeability and saturation flux density typically decreasing as temperature increases. Second, increased temperature can accelerate the crystallization process in amorphous materials, potentially causing irreversible changes to the core properties during extended testing periods.

Effective thermal management strategies must be implemented to maintain measurement accuracy. Active cooling systems, such as forced air or liquid cooling, have proven effective in dissipating heat during high-frequency testing. These systems must be carefully designed to avoid introducing electromagnetic interference that could affect measurement accuracy.

Temperature monitoring is equally important, with strategically placed thermocouples or infrared sensors providing real-time feedback on core temperature. Advanced testing protocols often incorporate temperature compensation algorithms that adjust for the effects of temperature on measured core losses.

The physical design of test fixtures also plays a crucial role in thermal management. Minimizing thermal resistance between the core and cooling medium, while maintaining electrical isolation, represents a significant engineering challenge. Materials with high thermal conductivity but low electrical conductivity are preferred for test fixtures.

For extremely high-frequency testing (above 500 kHz), pulsed testing methods may be employed to reduce average power dissipation and associated heating. These methods apply test signals in short bursts, allowing cooling periods between measurements while still capturing the high-frequency behavior of the material.

Standardization of thermal management protocols remains an ongoing challenge in the industry, with different laboratories employing varied approaches. This lack of standardization contributes to discrepancies in reported core loss values across different testing facilities, highlighting the need for comprehensive thermal management guidelines specific to high-frequency testing of amorphous soft magnetic alloys.