Solid-state transformers offer a way to fit power conversion into less space. For engineers designing the insulating barriers, busbar supports, standoffs and mounting plates inside those systems, that creates an important question: how can the assembly become more compact while maintaining electrical isolation and mechanical stability?
The answer starts with treating insulation as part of the architecture. Material grade, conductor spacing, local temperature and finished-part geometry need to be developed together in order to address this critical challenge.
Solid-state transformers are moving beyond the laboratory
In August of this year (2026), North Carolina State University announced that it had designed and tested a solid-state transformer capable of handling up to 1 MW in collaboration with the New York Power Authority and EPRI. The prototype was demonstrated on a real distribution feeder at EPRI’s laboratory in Lenox, Massachusetts. NC State identified data centers and electric vehicle charging among the applications that could directly benefit from the technology.
SSTs combine power electronics with a higher-frequency magnetic isolation stage. Operating the magnetic stage at a higher frequency can reduce its size, while the converters provide functions such as AC-to-DC conversion and control of power flow. Equipment manufacturers are also developing medium-voltage SST products for power distribution applications.
Those developments bring attention to the many parts surrounding the power electronics and magnetics. An insulating support, for example, may need to locate conductors, carry assembly loads and maintain separation throughout repeated thermal cycles.
Compact packaging changes the insulation problem
Reducing enclosure size does not necessarily require reducing every electrical spacing. It does, however, make those distances more consequential to the layout. Three issues deserve attention early.
Clearance and creepage are different design requirements
Clearance is the shortest distance through air between conductive parts. Creepage is the shortest distance along an insulating surface.
A mounting plate can provide adequate insulation through its thickness while the assembly still has an inadequate air gap or surface path. Holes, slots, metal fasteners and adjacent brackets all affect the geometry that must be evaluated.
Comparative tracking index, or CTI, describes resistance to surface tracking under a specified test. It informs material grouping for creepage calculations where the applicable standard uses that classification. It does not establish the required clearance or certify a part for a particular operating voltage. Working voltage, transients, pollution conditions and altitude also influence insulation coordination.
For a medium-voltage assembly, the governing equipment standard must determine the design requirements. Spacing examples developed for lower-voltage devices should not be transferred directly to an SST.
Switching waveforms affect insulation stress
The voltage across an insulating part is more informative than the system’s nominal voltage alone.
SST insulation can encounter repetitive switching waveforms with rapid voltage transitions, commonly described as high dv/dt. Research on medium-frequency transformer windings has examined how switching frequency and these transitions affect partial discharge and insulation lifetime. Those results concern the tested winding insulation; they do not establish a qualification for a machined laminate barrier.
Partial discharge is a localized electrical discharge that does not completely bridge the insulation. The practical implication for component design is to evaluate electric-field concentration and interfaces, including conductor edges, fasteners and gaps between materials. A short-duration dielectric-strength value alone cannot predict the assembled system’s behavior under repetitive switching.
Higher efficiency still requires a thermal plan
A smaller converter does not automatically run hotter. Its temperatures depend on losses, cooling and the paths available for heat to leave the assembly.
Compact packaging can nevertheless concentrate heat sources near insulating components. Engineers should evaluate the temperature at the support or barrier itself, including hot spots and thermal cycling.
Electrical insulation and heat conduction are separate material characteristics. A grade that tolerates elevated temperature is not necessarily effective at conducting heat away from a semiconductor or busbar. Where a component must perform both functions, the design needs relevant thermal-conductivity data as well as electrical and mechanical properties.
Compare properties under relevant conditions
A useful material review goes beyond the largest dielectric-strength number on a datasheet.
- Dielectric strength: Compare test method, specimen thickness, conditioning, temperature and direction relative to the laminate. Avoid multiplying a published volts-per-thickness figure by the finished thickness to establish a working-voltage rating.
- Tracking resistance: Request CTI for the exact product. Do not assume all glass-epoxy or glass-polyester grades share one value.
- Thermal performance: Distinguish glass-transition temperature, heat-deflection temperature, thermal endurance and a supplier’s stated service-temperature limit. They describe different behavior.
- Moisture response: Review absorption together with electrical properties after conditioning. A dimensional change and a change in insulation resistance can both matter.
- Flammability: Confirm the required classification at the relevant thickness and for the supplied formulation. UL 94 evaluates burning behavior under defined conditions; it does not establish dielectric performance.
- Frequency-dependent properties: Where relevant, request dielectric constant and dissipation factor at representative frequencies and temperatures.
Published values are useful for screening candidates. Selection also needs to account for the finished geometry and the assembly’s qualification requirements.
Where common laminates and plastics fit
The following comparison identifies reasons to evaluate each material family. It is a starting point for a grade-specific review.
| Material | Reasons to Evaluate | Selection Question |
|---|---|---|
| G-10 Glass Epoxy | Structural insulating parts requiring mechanical strength and electrical insulation | Does the exact product meet the thermal and flammability requirements? |
| FR-4 Glass Epoxy | Supports and barriers requiring a flame-retardant glass-epoxy formulation. | Are its CTI, thickness-specific flame rating and conditioned electrical properties suitable? |
| G-11 Glass Epoxy | Supports requiring mechanical performance at elevated temperatures | Which formulation and thermal rating are being supplied, and is flame resistance separately required? |
| GPO-3 Glass Polyester | Electrical barriers and supports where tracking and arc resistance are selection priorities | Does the exact grade provide the required electrical performance and mechanical stiffness? |
| Unfilled PEEK | Machined insulating components where temperature exposure and geometry justify evaluating a thermoplastic | Are creep, thermal expansion, tracking performance and the supplied formulation acceptable? |
Atlas Fibre’s glass-epoxy information distinguishes G-10, flame-retardant FR-4 and higher-temperature G-11.
Machining is part of the insulation design
A material’s published properties describe a test specimen. The installed component also has edges, holes, pockets, fasteners and manufacturing tolerances.
For thin barriers and mounting plates, drawing and process reviews should address:
- Flatness in the installed condition. Define whether flatness is inspected with the part free or restrained. Clamping a thin plate flat during machining does not establish its released shape.
- Minimum remaining sections. Identify critical webs, pocket floors and distances around holes. Thickness tolerance and stock variation need to fit within those limits.
- Edge and hole condition. Specify acceptable chipping, burrs and delamination where they could affect fit or the intended insulation geometry.
- Fastener interfaces. Review washers, inserts and counterbores as part of the electrical layout and mechanical load path.
- Inspection conditions. Define temperature and any required moisture conditioning when dimensions are sensitive to the environment.
For thermoplastic components, clamping pressure, machining heat and residual stress can affect the final dimensions. Manufacturer machining guidance emphasizes controlling these factors rather than treating plastics like metals.
Surface sealing or coatings, when required, should be specified and qualified as part of the insulation system. They should not be assumed to compensate for an unsuitable base material or inadequate geometry.
Settle the material questions before freezing the design
Early supplier discussions are most useful when they include the operating conditions and the drawing together.
Before committing to a prototype grade, establish:
- The working voltage across each component, repetitive peaks and transient requirements.
- The governing equipment standard and required insulation function.
- The local temperature range, hot spots and expected mechanical loads.
- The humidity, contamination and potential condensation exposure.
- The dimensions, surface paths and edge conditions that are critical to insulation.
- The exact material designation, acceptable substitutions and required documentation.
- The electrical and environmental testing that will qualify the assembled design.
A compact design benefits when material selection and manufacturability are resolved while the layout is still flexible. A change to a mounting hole, barrier thickness or fastener arrangement can affect more than the fit of one part.
Atlas Fibre supplies thermoset composite laminates and machines engineering plastics into finished components. For teams developing compact power-conversion equipment, an early drawing review can connect material requirements with stock thickness, part orientation, edge quality and achievable tolerances.
Developing an insulating barrier, support or mounting plate? Share your drawing and operating requirements with Atlas Fibre to discuss material options and machining considerations.