Magnetic Component Design Is Becoming More Application Specific

 

The design of electrical and electronic equipment is now more than ever dependent on the physical and electrical limitations of the systems in which they are supposed to operate. This is especially true for magnetic components, where minor deviations in frequency, current, voltage, winding laying or space availability have significant impact on the design.

Inductor and custom transformers are both key elements of power electronics and electrical systems in general. Although similar in their reliance on magnetism to store and transfer energy, they have significantly different sets of requirements to meet during the design process.

Moving Beyond Standard Component Specifications

Standard magnetic components are designed around standard electrical and mechanical specifications. This works well for circuits which have a set of typical requirements. However, designers of specialized equipment are often faced with the situation where catalog parts do not fit the allocated PCB space, operating frequency, voltage levels, thermal constraints and connection scheme.

This is why magnetic component engineering is shifting toward application-specific design.

A custom transformer, for example, can be dimensioned around specific turns ratio, winding configuration, insulation requirements, core material, operating frequency and geometry rather than fitting a standard component within a particular mechanical and electrical design.

The Role of the Inductor in Power Electronics

An inductor is an electrical component that stores energy in a magnetic field. It is related to circuits where current variation, filtering, energy storage, and electromagnetic interference are of concern.

The design of inductors is not simply a matter of winding a number of turns of wire around a core. Factors that must be taken into account in their design include current rating, saturation characteristics, winding resistance, core losses, operating frequency, temperature rise, and size.

Hence, different magnetic structures will give widely varying results even with nominally equal inductance values.

Toroidal, air-core, bobbin-core and PFC inductors are various types of inductors. Which type should be used depends on the electrical characteristics and physical size constraints of the application. CET Technology classifies inductor types into toroidal, air-coil, Common Mode Choke, drum/bobbin-core and PFC types.

Custom Transformers and Electrical Design Constraints

Transformer design presents another set of parameters to consider. The transformer has to provide for electrical isolation, voltage ratios, power, frequency, winding configuration, insulation, thermal properties, and core material.

For a special type of application, a transformer can be designed around these parameters instead of using an off-the-shelf design.

High-frequency transformer designs are a good example of this, as flyback, push-pull, forward-converter, half-bridge, and full-bridge circuits employ very different circuit relationships and require different characteristics from the transformer.

Lower frequencies often see the designer looking at power, insulation, form, and voltage as the parameters that define the circuit, leading to the use of EI and toroidal cores in their construction.

Engineering Starts With the Electrical Requirements

One of the most significant changes in magnetic component development is the increased focus on requirements definition before component selection.

For an inductor, engineers may define target inductance, maximum DC current, ripple current, peak voltage, and power conditions prior to designating an initial design. PFC inductor development, for instance, can have such characteristics during their initial design process.

Transformer development follows the same pattern. Voltage, current, frequency, power level, insulation requirements, winding arrangement, and available space can all influence the final construction.

This is especially important in the design of a component that has to fit within an existing enclosure, PCB layout, power supply arrangement, or industrial assembly.

Manufacturing Considerations in the United States

For U.S. engineering and procurement teams, component sourcing is also closely linked to manufacturing capacity, quality, documentation, and supply-chain planning.

Engineering and design specifications for magnetic components often entail tight tolerances, requiring careful selection of core materials, winding, insulation, terminations, and testing procedures to ensure consistency.

CET Technology, Inc. has been supplying standard and custom magnetic components to the OEM market since 1987, manufacturing transformers, inductors, coils, chokes, power supplies, and related components.

In turn, the broader manufacturing and sourcing strategy also features multiple production facilities and regional stocking strategies, which is especially important for OEMs that buy components in high volume over an extended period of time.

Where Inductor and Transformer Design Intersect

Although inductors and transformers differ in their electrical functions, there are many common engineering basics in their creation.

Similarities include core materials, winding construction, insulation, frequency response, thermal properties, and choice of materials. Both face challenges such as parasitic capacitance, winding resistance, magnetic saturation, and electromagnetic interference.

As a result similar knowledge is required for the design of both, focused more on the entire circuit in which the component will be used, rather than the individual characteristics of the inductor or transformer itself.

The difference between component selection and component engineering becomes less apparent in specialized equipment.

A More Engineering-Led Approach to Magnetic Components

A new direction in the development of magnetic components is dictated not only by the requirements of the associated electronics but also by their integrated application.

A single inductance can impose requirements on inductance, current and frequency, and power, and size characteristics. A specialized transformer will have specific voltage transformation ratios, insulation capabilities, power, and geometrical dimensions.

Thus, instead of using a standard set of components, one can take the reverse approach, specifying the electrical and mechanical requirements for magnetic components, after which one can determine what possible magnetic structures can be used.

Therefore, for companies in the United States that are engaged in the development of magnetic components, this is yet another competitive advantage in meeting the requirements of the electronics industry. The development of such components as transformers, inductors, and others is directly related to the characteristics of the equipment in which they are used.