Trends in Electromagnetic Component Design: Why You Shouldn’t Underestimate Magnetic Technology
This article describes the advancements on the electromagnetic components' designs, analysis, simulations, cores and wires
Electronic transformers, inductors and magnetic materials are ubiquitous in many applications, from power adapters, laptops & mobile devices, automobile electronics, LED lighting, medical electronics, industrial control, security systems, photovoltaic inverters, automobile charging stakes, UPS power sources, and digital audio equipment. But the enabling technology remains unsung.
For many designers, these magnetic and electromagnetic components are considered very “low tech." The reality is, however, that much technology and know-how is applied to designing and constructing these passive components.
Technological developments - energy efficiency, weight minimization, surface mounting, and miniaturization have been major factors in driving growth in this sector. Future growth in the markets for electronic coils, transformers, and other inductors will be driven by new, high-tech electronic components.
Developments in materials, winding techniques and equipment, and design solutions are creating new optimized solutions across a range of applications.
It All Starts with Design
Practical electromagnetic component design requires knowledge of electrical principles, materials, as well as economics. Small devices, for example, low-voltage transformers under 10kVA, may be designed using handbook data and pencil-and-paper calculations, specialist devices, and larger or mass-produced units require extensive computer-aided modeling (CAM).
Figure 1: Electromagnetic Field Simulation
Advanced Simulation and Design Builds from the Basics
Even the most sophisticated design and analysis have at their heart the fundamentals of magnetic and electrical circuits - Maxwell’s equations, Ampere’s law, Faraday’s law, Gauss’s law, and Lenz’s law. Best in class design software takes these fundamentals and apply today’s electromagnetic field simulation and modeling with sophisticated computation and visualization techniques. For example, ETAL harnesses the power of simulation software based on the finite element method to simulate low-frequency electromagnetic fields in a wide range of industrial components. Examples run from 2-D magnetic transient, AC electromagnetic, magnetostatic, electrostatic and DC conduction to electric transient solvers. It will accurately solve field parameters including capacitance, inductance, resistance, and impedance.
Once we have the results, we can then build a full 3D CAD drawing, and customers can then move forward with the mechanical and electrical design of their system without the need for physical samples of the finished component.
Figure 2: Nanocrystalline Common-mode Chokes Provide Damping of Noise Frequency Over a Wider Frequency Range – More Double the Range of Ferrite Alternatives
Component design teams can then create very accurate models of magnetic components within the CAD package. They can try-out the impact of different materials, wires, and air gaps, tuning the design to get as close as possible to the parameters required by the customer. Using simulation to tune the design allows optimum performance to be achieved without the need to create multiple prototypes.
With design and analysis based on solid engineering principles and state-of-the-art simulation techniques, designs can push the envelope by integrating new magnetic materials, wires, winding and manufacturing techniques at the earliest possible stage.
Innovative Magnetic Materials
For the electromagnets used in inductors, transformers, DC-DC converters, and the like, designers look for core material that delivers high permeability and maximum flux density. Iron and alloys like SiFe are the traditional starting point.
Ferrites — ceramic, homogeneous materials are composed of various oxides. Those with iron oxide as their main constituent exhibit excellent EMI protection against common mode and differential conducted noise since their insertion loss is proportional to a frequency — thereby showing no attenuation to signals, but high impedance to high-frequency noise.
For power conversion applications, working temperature, flux density, and frequency are the key parameters to select the proper material: from standard 60 to 100 deg C in handheld converters to -20 to 100 or -60 to 140 deg C for automotive or industrial applications. Converters operate at a wide switching frequency range, depending on voltage, power and cost constraints. Specific materials enable components to operate from just a few kHz through to hundreds of kHz and even MHz, providing high efficiency, compact converters.
Powder cores are distributed air gap cores that are primarily used in power inductor applications, specifically in switched-mode power supply (SMPS) output filters, also known as DC inductors. Other power applications include differential inductors, boost inductors, buck inductors, and flyback transformers.
Figure 3: Complete 3D CAD Tool Suites Offer The Capability To Create Production-level Drawings
Different core materials have particular advantages for certain applications. For lowest loss, core loss is the key factor, whilst designs requiring minimum core size, such as a DC bias dominated design, should use materials with the highest flux capacity. Saturation is another property to consider, with available materials providing trade-offs between low losses and reasonably high saturation (0.8T) at a low cost, up to higher-priced, high saturation material (1.6 T). High saturation is advantageous where inductance under load is critical.
An advance on powder technologies, new amorphous and nanocrystalline magnetic cores allow smaller, lighter and more energy-efficient designs in many high-frequency applications for inverters, adjustable speed drives, and power supplies. Amorphous metals are produced by using special technology where molten metal is cast into thin solid ribbons. Since the material has no crystalline magnetic anisotropy, amorphous magnetic metal has high permeability.
When compared with conventional crystalline magnetic materials, amorphous magnetic cores have superior magnetic characteristics, such as lower core loss. These cores offer superior design alternatives when used as the core material.
Nanocrystalline alloys offer a unique combination of high permeability with large flux density and low losses at high frequencies. Operational temperatures of up to 180°C are possible. Materials like this enable the construction of chokes and transformers in much smaller dimensions than is possible using ferrite based assemblies. Common-Mode chokes, in particular, benefit from the high permeability, because the amount of copper wire can be reduced, thus reducing copper losses and component size.
Figure 4: Advanced Design and Innovative Materials Bring New Possibilities for Custom Magnetic Components
Why Wire is Important
Another development facilitating smaller form factors is the introduction of triple-insulated wire. This allows windings to be laid on top of each other, giving mains isolation in a smaller form factor. This technique meets all the leading international safety codes and enables transformers to be manufactured to meet safety isolation standards without the need for margins and tape barriers. With conductor diameters ranging from 0.2 mm to 1 mm, the increased winding space permits smaller transformers to be designed and reduces manufacturing time and cost.
Advances in magnetic materials, wire, winding techniques, and equipment, can be fed back rapidly through accurate simulation tool and 3D CAD solutions, to create new optimized solutions across a range of applications, from standard products, through custom designs for signal transformers, LAN & xDSL Modules, Planar Transformers, Inductors and Modules, and CANbus Chokes.
Unsung they may be, but magnetic components help manufacturers to achieve designs that match customers’ expectations much more closely and achieve them more quickly at a lower cost.
About the Author
Andrew Adams is the Technical Manager of ETAL Group, one of the leading suppliers of in-house developed high-performance magnetic components, primarily transformers and inductors; the company conducts operations through local offices in Sweden, Estonia, UK, China, and Sri Lanka, and through distribution partners in an additional 20 or so countries.
This article originally appeared in the Bodo’s Power Systems magazine.