Three-phase resonant converters and planar magnetic integration

PREMIUM SA · ENGINEERING INSIGHT · HIGH-DENSITY RESONANT CONVERSION · 2026

Three-phase resonant converters and planar magnetic integration

Topologies, current-balancing control and 1 MHz planar magnetics: the route to ultra-high power density in DC-DC.

Executive summary

Resonant converters are the cornerstone of high-efficiency DC-DC stages in EV fast chargers, server supplies and telecom infrastructure. Their LC resonant network shapes the waveforms to achieve soft switching —ZVS on the primary and ZCS on the secondary rectifiers—, virtually eliminating switching losses and enabling high-frequency operation with smaller passives.

Moving from single-phase to three-phase interleaved with a 120° phase shift naturally cancels the output current ripple through phase superposition, dramatically shrinks the output capacitor filter and spreads thermal losses across the semiconductors. In exchange it triples the magnetic component count and exposes the system to inter-phase current imbalance from manufacturing tolerances (typically ±10 %). This article walks through the topologies (LLC, CLLC, LCC, SRC), the balancing strategies (floating star, CPAB), hybrid PFM+PSM modulation, and the planar magnetic integration that —together with AlN conductive cooling— enables 1 MHz operation at ultra-high power density.

Prototype and improvement figures are traced to the peer-reviewed literature listed at the end; material properties to public literature. Where a figure lacks verifiable backing, it is explicitly flagged as pending source confirmation.

> 98 %Peak efficiency in a 30 kW three-phase LLC EV charger (SiC)

120°Phase shift that cancels output ripple and shrinks the filter

< 5 %Phase imbalance with floating star + CPAB control

1 MHzTarget frequency enabled by WBG and planar integration

Why three-phase: 120° ripple cancellation

Single-phase resonant converters perform well at low power but exhibit high output current ripple that subjects the filter capacitors to severe thermal and ripple-current stress, forcing them to be oversized. The three-phase interleaved structure removes this bottleneck: operating the three legs with a 120° phase shift between gating signals, the sum of the phase-shifted rectified currents yields an almost continuous power flow with very low residual ripple. The immediate effect is a drastic reduction in the size and capacitance of the output filter, with the corresponding gain in power density and better thermal distribution across the semiconductors.

The schematic below places the full conversion chain and anticipates where power density is won: the integrated planar magnetic core.

Three-phase resonant network topologies

The dominant high-frequency topologies are LLC, CLLC and LCC, each with a distinct gain, impedance and bidirectional profile. In the LLC, each phase integrates a series resonant inductor (Lr), a series capacitor (Cr) and the transformer’s parallel magnetizing inductance (Lm); below the resonant frequency, Lm participates and provides a boost capability. The resonant frequencies are governed by fr1 = 1/(2π·√(Lr·Cr)) and fr2 = 1/(2π·√((Lr+Lm)·Cr)), and the inductance ratio is m = Lm/Lr; operating fs near fr1, the converter reaches its peak-efficiency point with unity gain.

Table 1 — Comparison of resonant topologies (traced to literature).

Topology	Soft switching	Bidirectionality	Gain range	Typical application
LLC	Full primary ZVS; secondary ZCS below resonance	Asymmetrical; high reactive current in reverse	Moderate; strongly load-dependent far from resonance	Unidirectional EV chargers, server/telecom PSU
CLLC	Symmetrical ZVS in both power-flow directions	Completely symmetrical (dual tanks)	Wide; optimized for variable battery voltage	Bidirectional EV chargers, V2G interfaces
LCC	ZVS over a wide range down to zero load	Asymmetrical (Cp alters reverse gain)	Exceptionally wide; excellent at light load	High voltage, capacitor charging, wide-range adapters
SRC	Primary ZVS above resonance	Symmetrical	Narrow; gain strictly bounded below unity	Fixed-ratio DC-DC, narrow-range bus converters

On the primary connection, the delta option (Δ-Cr) reduces the tank current by a factor of √3 —cutting the winding copper loss to one third versus the parallel star— but imposes a penalty: the volt-second stress on the high-frequency transformer also rises by √3.

Floating star (Y-primary) and natural current sharing

The most common configuration connects the three transformer primaries in a star with a common floating neutral point. This connection dynamically modulates the neutral-node voltage, reshaping the resonant currents toward a more rectangular than sinusoidal waveform: by flattening the peaks, it lowers the peak and RMS current versus a single-phase converter of equal power, reducing conduction losses. More importantly, it provides a natural current-balancing capability far superior to independent parallel converters.

Self-compensation and MTBF. Under resonant-capacitor tolerance or degradation (a common failure mode in high-temperature environments), the floating neutral shifts dynamically to accommodate the drift, preventing localized thermal runaway on an ageing phase. This passive, zero-cost balancing limits the mean current mismatch to under 15 % without any active control, and extends system MTBF.

Current imbalance and active mitigation

Despite the star node’s natural balancing, passive-component manufacturing tolerances (typically ±10 %) shift each phase’s impedance and produce thermal asymmetry and extra output-capacitor ripple. Hardware solutions (balancing transformers) add loss and volume, so active control is preferred:

CPAB (Current Phase Angle Balancing): directly regulates the phase angles of the resonant currents with dedicated PI loops to hold an exact 120° spatial displacement, limiting residual mismatch to under 5 % even under severe tolerances. It outperforms the historical TCB (Trigonometric Current Balancing), which has poor transient response.
RMS-based real-time algorithm: measures the individual RMS currents and linearly adjusts the input-voltage phase shifts (V and W channels relative to the U reference), reducing the imbalance factor to under 2 % across the full frequency range.
Phase-Shift Modulation (PSM): in two-module parallel three-phase structures, PFM regulates voltage and PSM shares current; a 30° displacement between modules minimizes total output ripple.

Stable implementation demands careful loop design: in a reference application, the voltage loop (PFM) uses a PI compensator with a 5 kHz crossover and 96° phase margin, while the current-sharing loop (PSM) uses integral compensators with a lower 500 Hz crossover and 91° margin to avoid loop interaction. With a physical mismatch of LrA=20 µH and LrB=16 µH, without active sharing the phase shifts lock at an identical 40.5°; with PSM active the controller dynamically diverges them (41.8° and 39.2°) and restores current symmetry.

Hybrid PFM + PSM modulation

Conventional PFM control varies the switching frequency to regulate voltage, but very wide voltage ranges (an EV charger may span 200 V to 1000 V) force it to sweep a huge frequency spectrum, complicating the EMI filter, drivers and magnetics, and increasing circulating-current losses far from resonance. The hybrid scheme uses PFM below resonance (boost mode, high efficiency) and activates PFM+PSM above it: shifting the phase angle between legs generates a three-level voltage waveform that adjusts the tank’s effective excitation, minimizing the frequency range and reactive circulating energy. The VCR-based VFSHC variant switches modes without transients and completely eliminates the «inoperative region» of conventional hybrid schemes.

Planar magnetic integration: three in one

The main drawback of three-phase is the escalation of magnetic components: three independent inductors and three transformers raise volume, cost and assembly complexity. Planar integration merges them into a single structure. Splitting the primaries across the legs of a three-column core, the sum of the 120°-shifted fluxes cancels in the center leg, which dramatically reduces core losses and simplifies thermal management. With WBG semiconductors (SiC/GaN) the frequency rises to the 500 kHz–1 MHz+ range, enabling PCB copper windings and very low-profile planar cores.

Not all geometries are equal. The classic square integrated core suffers asymmetrical reluctance paths —the center leg is shorter than the outer ones— which induce phase imbalance. An elegant spatial solution is the cylindrical planar core, which enforces complete three-dimensional symmetry and aligns the reluctances of the three phases. For very high currents, the matrix transformer (series primaries, parallel secondaries) distributes voltage stress and heat dissipation.

Table 2 — Planar magnetic integration strategies (traced to literature).

Strategy	Core complexity	HF loss reduction	Reluctance symmetry	Engineering challenge
Discrete parallel cores	Low (standard cores)	Low (no flux cancellation)	High (independent paths)	Large volume, low density, high cost
Square integrated core	Moderate (single E-core)	Moderate (center-leg cancellation)	Low (outer legs longer)	Asymmetry → phase imbalance
Cylindrical symmetrical core	High (custom geometry)	High (optimized uniform flux)	High (complete 3D symmetry)	Custom manufacturing and winding
Matrix transformer	High (multi-core series-parallel)	High (distributed core volume)	High (symmetrical PCB routing)	High secondary leakage inductance; routing

Core thermal management at 1 MHz: the role of AlN

As frequency rises to 1 MHz, ferrite core losses grow and push planar components toward their thermal margins. The reflex of inserting a metal piece (copper, aluminium) to cool the transformer internally is counterproductive: the alternating magnetic field induces severe eddy currents in the metal, sending losses up. The solution is a material that conducts heat but insulates electrically: aluminium nitride (AlN).

AlN combines a high thermal conductivity —on the order of 150–180 W/(m·K), and up to 230 W/(m·K) in premium commercial grades, comparable to some metals— with high dielectric strength. It is also 7 to 10 times the thermal conductor of alumina (Al₂O₃, ~30 W/(m·K)), cheap but poor, and unlike beryllium oxide (BeO, ~260 W/(m·K)) it is non-toxic. Being a non-conductive ceramic, interleaving thin AlN plates (e.g., 0.5 mm) within the ferrite block stack creates internal conductive cooling channels without inducing parasitic currents, draining heat from the inner —typically hottest— regions and lowering the core’s peak temperature.

Rigour on the improvement figures. Thermal-optimization studies report that a 1 MHz ferrite core with embedded 0.5 mm AlN layers would admit an increase on the order of 167 % in its admissible heat-generation density (theoretical models in the 173–187 % range), and that dedicating 30 % to 35 % of the core volume to AlN would maximize the sustainable useful flux. These specific figures could not be verified against independent public literature and are carried over as a simulation-study datum pending source confirmation; the AlN material properties are supported by materials literature. Recommendation: validate experimentally before publishing the improvement figures as a closed datum.

WBG semiconductors: the enabler and its constraints

High-frequency operation is made possible by wide-bandgap semiconductors. Versus silicon (Eg 1.1 eV, critical field 0.3 MV/cm, mobility 1400 cm²/V·s), SiC (3.3 eV, 3.0 MV/cm, 900 cm²/V·s, excellent thermal conductivity) and GaN (3.4 eV, 3.3 MV/cm, 2000 cm²/V·s) allow thinner drift regions, lower Rds(on) and blocking voltages from 650 V (lateral GaN) to 1200 V+ (vertical SiC).

The price is demanding hardware design. dv/dt of hundreds of volts per nanosecond excites circuit parasitics, generating oscillations, EMI and instability. In E-mode GaN, with a narrow gate window (−10 V to 7 V) and low threshold (Vth < 2 V), gate crosstalk can trigger catastrophic false turn-on events. The designer must use gate drivers with active Miller clamp, Kelvin source connections and strictly symmetrical PCB layouts to suppress spikes and keep the soft-switching boundaries.

Validated prototypes

Industry has built and measured several platforms that confirm the architecture’s advantages:

Table 3 — Published prototypes (parameters and achievements, traced to literature).

Platform	Topology	f_sw	Voltage / power	Efficiency and achievement
30 kW EV charger	Three-phase interleaved LLC (SiC)	135–250 kHz	Vin 650–850 V; Vout 200–1000 V	Peak > 98 %; full load > 97 %
10 kW high-density CLLC	Three-phase CLLC	High frequency	800 V DC bus	Peak 97.5 %; cylindrical planar; minimal imbalance
500 W single-stage AC-DC	Matrix switch + LLC	465–547 kHz	Vin 100 V AC; Vout 130 V DC	Peak 97 %; PF 0.99; THD 3.95 %
4 kW bidirectional	Three-phase LCC	High frequency	320 V ↔ 28 V battery	Peak 92.2 %; range 0–12.5 A / 0–142 A
3.6 kW grid-tied	Interleaved LLC	Synchronous frequency	48 V output	CPAB controller with verified stable sharing

Synthesis — Premium SA design criterion

Translated into project recommendations, the three-phase resonant architecture is ordered as follows:

Bidirectional → CLLC: for V2G and grid storage, CLLC over LLC guarantees symmetrical gain and identical soft-switching boundaries in both directions.
Passive balancing → floating star: in high power with expected ageing or tolerances, the floating Y node provides zero-cost balancing (<15 %) and drift self-compensation.
Fine balancing → CPAB software: for critical applications, CPAB alongside the floating node drives the mismatch below 5 % with no extra hardware.
Wide range → hybrid PFM+PSM (VFSHC): limits the frequency spectrum, optimizes the planar magnetics and avoids the inoperative region.
Density → planar magnetics + AlN: cylindrical or matrix cores to cancel flux and spread heat; AlN conductive cooling to raise the thermal limit at 1 MHz without inducing eddy currents.
WBG → disciplined layout: active Miller clamp, Kelvin source and PCB symmetry to tame SiC/GaN dv/dt.

Sources and traceability

Premium SA internal catalogue: block B4 (resonant and multilevel topologies, manual_avanzado_diseno), B8 (passive/magnetic components), B7 (advanced thermal management). Consistent with the Premium article «Multilevel Inverters» v1.0 (no overlap: that one covers the inverter stage; this one, the resonant DC-DC stage).

External technical literature (selection):

Three-phase architecture and control: studies on three-phase LLC/CLLC/LCC, current sharing, CPAB and hybrid PFM-PSM modulation (IEEE/MDPI/ResearchGate; Wolfspeed 30 kW SiC charger).
Planar integration: cylindrical symmetrical core and matrix transformers for high-frequency three-phase LLC (MDPI Energies; magnetic-integration thesis, White Rose).
AlN properties: materials data (Kyocera, Precision Ceramics, substrate manufacturers): λ 150–230 W/(m·K) by grade; alumina ~30 W/(m·K); BeO ~260 W/(m·K), toxic; CTE matched to Si.
AlN power-improvement figures: simulation study cited in the source material — pending primary-source confirmation before publication as a closed datum.

About Premium SA

Premium SA is a Barcelona-based manufacturer of electronic power converters for railway, industrial and energy applications. With more than 900 standard product designs and over 40 years of operational experience, Premium SA supplies DC/DC converters, DC/AC inverters, AC/AC frequency converters, battery chargers, rectifiers and UPS systems from 50 W to 72 kW.

The D2x / DFR methodology integrates topology, digital control and the magnetic-thermal architecture as coupled decisions from the conceptual phase, with a preference for custom solutions, WBG semiconductors and traceable experimental validation.

Application Notes, Energy, Sin categoría

Design, calculation and simulation of planar transformers

PREMIUM SA · ENGINEERING INSIGHT · HIGH-FREQUENCY MAGNETICS · 2026

Loss physics, winding structures, parasitics, insulation standards and the open-source software ecosystem for high-frequency magnetics.

Executive summary

The drive for higher power density, efficiencies above 98 % and ultra-thin profiles has pushed the transition from the conventional wire-wound transformer to the planar transformer: photolithographically etched copper traces on multilayer PCB or foils, coupled to low-profile ferrite cores. The change is not just form factor; it redefines high-frequency electromagnetic losses, parasitic dynamics and the validation methodology.

This article systematizes advanced planar-transformer design: the loss physics (skin effect, proximity and the Dowell model), turns-number optimization, the interleaved winding structures that control the magnetomotive force, leakage-inductance and inter-winding-capacitance management, experimental and finite-element validation, insulation-standard compliance, and the software ecosystem —with particular attention to the open-source tools that enable first-class engineering without proprietary licences, consistent with Premium SA’s preference for open, auditable software.

All figures and tools are traced: to peer-reviewed technical literature (application notes, DTU/Ouyang papers, IPC/IEC standards) and to verified open-source repositories. The formulas are the classic ones of the domain.

≈ ⅓Planar profile (~10.7 mm) versus 30–40 mm conventional

> 98 %Efficiency of the 1 kW / 1 MHz LLC with full integration

< 1 %Hybrid analytical-FEA model error vs 3D transient

−75 %Leakage inductance reduction with simple interleaving

Planar versus conventional: what changes

Conventional round-wire, Litz or foil transformers on PQ/ETD bobbins have severe limitations above 100 kHz, and winding variability introduces parasitic spread that hampers industrial repeatability. The planar replaces coils with copper traces on multilayer PCB or foils coupled to low-profile EQ/ER/E-LP cores. The most visible consequence is geometric; the most valuable, repeatability.

Table 1 — Conventional versus optimized planar transformer (traced to literature).

Parameter	Conventional (PQ32/35)	Planar (EQ38/8/25)	Engineering implication
Profile height	30–40 mm	≈ 10.7 mm (≈ ⅓)	Integration into very low-profile boards (brick)
Weight	High	≈ 3× lighter	Critical in transport and aerospace
Parasitic repeatability	Low (high spread)	Very high (photolithography)	Enables precise tuning of LLC tanks
HF conduction losses	High (inefficient packing)	Low if Rac is optimized	Better dissipation and overall efficiency
Prototyping flexibility	Very high (rewind by hand)	Low (any change = new PCB)	Forces simulation before fabrication

That last row sets the method: since any minor change requires a new PCB, planar design does not allow bench trial-and-error. It demands rigorous analytical modelling and simulation before going to production.

Systematic design methodology

The move to planar is not the geometric replica of a wire transformer: it requires a structured flow that audits the electrical, thermal and mechanical specifications and adapts them to PCB physics.

Table 2 — Planar design workflow (eight stages).

Stage	Key action	Critical parameter
1 · Base-design audit	Collect V, P, f, Lm, Llk, insulation, temperatures	Thermal and electrical targets to replicate/improve
2 · Core and material	Planar geometry (EQ/ER/E-LP) and ferrite (N87/N95/3C95/3F3)	Balance hysteresis loss vs available height
3 · Number of turns	Np, Ns from Faraday’s law and ΔB max	Fewer turns → less copper but more core
4 · Copper thickness	Size h according to skin depth δ	Avoid oversizing (aggravates proximity)
5 · Stack-up	P/S/shield sequence and interleaving	Determines Llk, Rac and global losses
6 · Trace width	Carry the DC and AC current density	Keep ΔT within safety limits
7 · Electrical/thermal validation	FEA or advanced analytics of HF losses and T	Spot hotspots before fabrication
8 · PCB fabrication	Vias, insulation slots, export Gerber	Manufacturability and insulation compliance

Loss physics: skin, proximity and Dowell

Accurate conduction-loss calculation is the greatest challenge in HF magnetics. Two coupled phenomena govern it. The skin effect concentrates current in a surface layer of depth δ = √(ρ/(π·μ·f)); for copper at 70 °C it reduces to the practical rule δ ≈ 2.276/√f mm. The resistance increase from this effect is Rac/Rdc = ξ·[sinh(2ξ)+sin(2ξ)]/[cosh(2ξ)−cos(2ξ)], with ξ = h/δ the normalized thickness: when ξ > 2, the conductor centre barely conducts and thickening the copper stops helping.

The proximity effect is more damaging. When layers are stacked, the fields of neighbouring conductors induce cross eddy currents. Dowell’s model for the m-th layer adds a second term scaling with (m²−1), where m is the layer’s MMF factor. Because that term grows quadratically with layer position, losses in stacks with many continuous non-interleaved layers explode. And since real currents are PWM, not sinusoidal, the resistance must be evaluated over the harmonic spectrum —P_AC = Σ Rac(n·fs)·I²rms(n)—: high-order harmonics, with very small δ, dissipate a lot even at moderate amplitude.

The optimal number of turns. Increasing N lowers the flux density ΔB and, via Steinmetz (Pv = K·f^α·ΔB^β, with β≈2–3), reduces core losses; but it demands narrower traces or more layers, raising Rdc and, through Dowell’s m, Rac. The optimum is not to eliminate one term but to balance them: the absolute loss minimum occurs when the copper losses are held at a factor β_loss = P_copper/P_core of the ferrite losses. It is the designer’s analytical tuning criterion.

Winding structures: interleaving as the lever

The way to tame proximity losses is to alter the spatial field distribution in the core window, abandoning simple non-interleaved stacks. Interleaving alternates primary and secondary layers with opposite current directions in adjacent layers, cancelling the net field and reducing Dowell’s m. The figure below compares three stack-ups and their MMF profile.

calculation — Figure 1 — Winding stack-up and MMF profile. Interleaving lowers the per-layer peak MMF and, with it, proximity losses and leakage.

The advanced symmetric structure 0.5P-S-P-S-P-S-P-S-0.5P —with the outer layers at half-turn and connected in parallel— forces multiple MMF zero-crossings, keeping m≈0.5–1 uniformly and minimizing both Rac/Rdc and the stored leakage energy. For fractional ratios or extreme thermal performance in the MHz range, the half-turn structure implements 180° traces in parallel on the outer layers, splitting the current and halving the peak field. And at high current, the interleaved serpentine winding snakes across several legs, maximizing window use without extra interconnection layers.

Table 3 — Winding structures and their behaviour (traced to literature).

Structure	MMF profile	Rac/Rdc	Leakage Llk	Routing / vias
Non-interleaved (P-P-P-P-S-S-S-S)	Linear ramp; peak at interface	Very high (accumulates m)	Very high	Minimal (no crossings)
Simple interleaving (P-S-P-S…)	Sawtooth; moderate peaks	Low (m≈1)	Reduced up to −75 %	High (alternating layers)
Advanced symmetric (0.5P-S…0.5P)	Attenuated; cancellation at outer faces	Absolute minimum (series-parallel)	Very low and controlled	Very high (parallel vias, symmetry)
Half-turn	Shifted and symmetric to axis	Very low (m≈0.5)	Minimal for a given insulation	Very high (fractional geometry)

Parasitics as design variables: leakage, capacitance and EMI

The planar’s tight spatial coupling maximizes mutual inductance but demands treating parasitics as active variables. Leakage inductance Llk arises from flux that closes through the window without linking both windings. In hard switching (full bridge, flyback) it is a harmful parasitic that causes overvoltages and demands snubbers; it is minimized with full interleaving and thin dielectrics. But in LLC resonant converters it is exploited: a controlled Llk is deliberately designed to act as the series resonant inductor Lr, removing a discrete component and gaining density. To tune it, magnetic shunts are inserted or the inter-layer dielectric spacing (Δh) is adjusted, which raises Llk linearly.

The high-frequency design dilemma. Reducing leakage forces primary and secondary close together, which raises the inter-winding capacitance C_inter. Under the primary’s fast dv/dt, C_inter injects common-mode displacement currents into the secondary, generating conducted EMI that demands bulky filters. It is broken with electrostatic shielding (a thin, slotted copper layer —to avoid shorting the flux— tied to a quiet ground) or with an auxiliary cancellation winding of opposite polarity (−dv/dt) that nulls the net common-mode current.

Validation: leakage measurement and hybrid analytical-FEA calibration

In a high-performance planar, Llk is under 1 % of the magnetizing inductance (often 0.1–0.2 %, in nanohenries), of the same order as the instrument leads’ own inductance. It is measured with the direct short-circuit method (a wide copper bar across the secondary + impedance analyzer at the decade of the switching frequency) or, without an HF analyzer, with the turns-ratio and AC-deviation method. In both cases it pays to build test fixtures with planar contacts and symmetrical coaxial traces to calibrate open/short at the device plane.

The one-dimensional Dowell model fails on real traces: concentric spirals concentrate the DC current at the inner radius (spirality effect), raising the real Rdc. The hybrid analytical-numerical methodology solves this without the cost of a full 3D transient: the ideal arc is computed (Rca = 2π/(σ·h_cu·ln(r₂/r₁))), the real resistance is extracted by static DC FEA with quarter symmetry, a calibration factor (Rca/R₊) is obtained and injected as a coefficient into the AC-loss formula. The result agrees with 3D transient simulations (Ansys Maxwell) within under 1 % error, in microseconds instead of hours.

Insulation and standards: clearance, creepage and IEC 60664-1

The proximity of high- and low-voltage traces demands strict compliance with dielectric standards. Clearance is the through-air distance (prevents direct arcing); creepage, the leakage path along the solid surface (prevents conductive carbonization). IPC-2221 sets minimums up to 500 V and adds a linear surcharge above that; IPC-9592, specific to power conversion, imposes more conservative criteria. High-CTI materials tolerate smaller creepages.

Distances are not read from a static table: IEC 60664-1 requires evaluating the real environment. The pollution degree (PD2 common in industry) can be reclassified to PD1 with conformal coating or potting, drastically reducing the required creepage. The overvoltage category (OVC) sets the primary clearance on mains. And altitude penalizes: above 2000 m the lower dielectric strength of air forces multiplying the clearance, with a factor of about 1.48 at 5000 m —relevant in mountain railway, high-altitude solar and avionics. Physically, creepage is multiplied by milling through slots in the FR4 between primary and secondary, forcing the leakage path to go around the cut, or by interposing insulating barriers.

Software ecosystem: open and commercial

The coupled complexity of the HF field has produced a mature software ecosystem. Premium SA prioritizes, where they meet requirements, open-source and auditable tools: they enable first-class engineering with no lock-in or licence cost, and their verifiable code fits the traceability that regulated sectors demand.

On the open side, the OpenMagnetics project stands out —a working group of the PSMA magnetics committee—: its MKF compute engine (C++) is exposed in Python via PyOpenMagnetics/PyMKF and operates on the neutral MAS format (Magnetic Agnostic Structure, a JSON schema describing requirements, construction and results, with insulation coordination per IEC 62368-1/61558). python-planar-magnetics (on PyPI) generates planar spirals respecting DRC rules, estimates Rdc correcting for spirality, and exports to KiCad (S-expressions) and DXF. For full FEA, ONELAB integrates Gmsh (meshing), GetDP (eddy-current fields coupled to SPICE) and Elmer (3D multiphysics in parallel, couplable to OpenFOAM for conjugate thermal). The Ansyas bridge (Synopsys–Würth collaboration) connects MAS to Ansys Maxwell via PyAEDT.

Table 4 — Software for planar magnetics design (verified).

Suite	Licence	Base / environment	Capability for planars
PyOpenMagnetics / MAS	Open source (MIT)	Python wrapper · C++ MKF engine	Proximity/skin losses, MAS JSON schema, SVG plotting
python-planar-magnetics	Open source	Parametric Python scripting	DRC spirals, Rdc correction, KiCad/DXF export
ONELAB (GetDP/Gmsh/Elmer)	Open source (GPL)	General-purpose FEA + SPICE	Coupled 2D/3D eddy current and conjugate thermal (OpenFOAM)
Ansys Maxwell	Commercial	Reference 3D EM FEA	Nonlinear hysteresis, bidirectional thermal-mechanical coupling
COMSOL / CST	Commercial	Multiphysics FEA / FEM-FIT-TLM	Coupled multiphysics; fine EMC validation
PI Expert (Planar Builder)	Commercial (Power Integrations)	Automated cloud synthesis	Stack-up, core, widths, clearance/creepage and Gerbers

Synthesis — Premium SA engineering recommendations

Tuned copper thickness: keep h ≤ 2δ at the working frequency; in the MHz range, thin foils or 1–2 oz copper interleaved, never generic heavy copper.
Always interleave the stack: avoid continuous MMF ramps; prioritize symmetric structures (0.5P-S…0.5P) or half-turn to minimize proximity and leakage.
Parasitics by topology: in LLC, design Llk as the resonant inductor (removes the discrete part); in hard switching, minimize Llk and break C_inter with electrostatic shielding to a quiet ground.
Hybrid analytical-FEA flow: calibrate the Rac equations with a geometric factor extracted from static DC FEA; enables Pareto optimization with <1 % error versus the 3D transient.
Insulation by real environment: size clearance/creepage with IEC 60664-1 (PD, OVC, altitude); mill slots in the FR4 and evaluate conformal coating to reclassify PD2→PD1.
Open software first: OpenMagnetics/MAS and python-planar-magnetics for synthesis and losses; ONELAB/Elmer for FEA; reserve commercial suites for final multiphysics validation.

Sources and traceability

Premium SA internal catalogue: block B8 (passive/magnetic components), B7 (thermal management), B4 (resonant topologies). Companion to the Premium article «Three-phase resonant converters and planar magnetic integration» (that one, system-level integration; this one, planar-transformer design methodology).

External technical literature and tools (selection):

Losses and design: Dowell model; loss and leakage optimization in planars (DTU / Ouyang); Texas Instruments application notes (Topic 4, Designing Planar Magnetics).
Case studies: 1 kW / 1 MHz one-eighth-brick LLC (TI SSZTD94); 1 W ultra-flat isolated supply TIDA-00688 (TI TIDUB83).
Insulation: IPC-2221 / IPC-9592; IEC 60664-1 (insulation coordination; altitude factor ≈1.48 at 5000 m); IEC 62368-1.
Open software (verified): OpenMagnetics / MAS / PyMKF (PSMA Magnetics Committee WG; IEEE-PELS, 40+ models); python-planar-magnetics (PyPI, dzimmanck); ONELAB / GetDP / Gmsh / Elmer; Ansyas bridge (Synopsys–Würth).

About Premium SA

The D2x / DFR methodology integrates magnetic design —including parasitic co-design and simulation verification— from the conceptual phase, with a preference for open-source, on-premises and auditable tools, and traceable experimental validation compliant with the standards of regulated sectors.

Application Notes, Energy

What is an Electronic Fuse (eFuse) and Why Is It Replacing Conventional Fuses in Industrial Panels?

Engineering Insight · eFuse

What is an Electronic Fuse (eFuse) and Why Is It Replacing the Conventional Fuse in Industrial Control Panels?

By the Premium PSU technical team · May 2026 · Reading time: 7 minutes

Born in Barcelona, Powering the World

45 min

Diagnosis with conv. fuse

<8 min

Diagnosis with eFuse

−82%

Diagnosis time reduction

10–100 µs

MOSFET switching time

ENGINEERING INSIGHT

What is an electronic fuse (eFuse) and why is it replacing the conventional fuse in industrial control panels?

By the Premium PSU technical team · May 2026 · Reading time: 7 minutes

Keywords: electronic fuse, eFuse, DIN rail, control panel, selective protection, electrical enclosure

Inside any industrial control panel, hidden among terminal blocks and PLCs, there are dozens of conventional fuses. For decades they have served a simple purpose: to blow when the current exceeds the rated limit. Yet that protection model — passive, slow and silent — is becoming obsolete in the face of modern automation system requirements.

The electronic fuse, also known as an eFuse or Electronic Circuit Breaker (ECB), does not blow. It detects overcurrent in microseconds, switches off the circuit electronically, indicates which channel has faulted via LED or digital signal, and can reset automatically once the root cause of the fault has cleared. This article explains how it works, when to apply it, and which parameters to evaluate when selecting the right model.

A counterintuitive technical decision: an eFuse costs between €12 and €25 per protected channel versus €0.50–2.00 for an equivalent conventional fuse. The paradox is that the eFuse proves more cost-effective in any installation that experiences more than 3–4 circuit faults per year. The reasons lie in the real cost of each intervention, not in the price of the component.

The real problem with conventional fuses

A conventional fuse does exactly what its name implies: it melts to interrupt the circuit. This simplicity carries a cost that rarely appears in the distributor’s catalogue:

High diagnosis time: when a fuse blows, the operator must identify which of the many fuses in the panel has failed, test each one with a checker or inspect them visually, locate the correct spare in stock, and reinstall it. In a panel with 50 circuits, this process can take 20–60 minutes.
No indication of root cause: a blown fuse gives no information about whether the fault was a momentary short circuit (electromagnetic noise, inrush current) or a sustained overload pointing to a real load defect. The technician does not know whether to reset or whether there is an underlying fault to repair.
No automatic selectivity: if the trip current is not properly coordinated with the PSU characteristic curve and the other protective devices, the upstream fuse may blow before the one protecting the faulty branch, causing a wider outage than necessary.
Spare parts inventory cost: every fuse rating (0.5 A, 1 A, 2 A, 4 A, 6 A, 10 A…) requires stocking spare units. In installations with many different ratings, managing the spares inventory consumes time and money.

The combined effect of these factors makes the conventional fuse a significant source of operational cost in industrial installations with high-density 24 VDC circuits.

How an electronic fuse works

An eFuse is essentially a controlled electronic switch. Its basic architecture combines three elements:

Power MOSFET: acts as the switching element. When the controller detects an overcurrent, it turns the MOSFET off in microseconds (typically 10–100 µs), with no electrical arc and no mechanical wear.
Integrated current sensor: continuously measures the output current of each channel. The measurement is analogue or digital (resistive shunt + ADC) with sufficient resolution to distinguish between a mild overload, a severe overload, and a short circuit.
Controller with configurable trip logic: compares the measured current against the user-set threshold (via potentiometer, DIP switch, or digital interface) and triggers channel opening when the limit is exceeded, following the desired time curve (instantaneous for short circuits, time-delayed for overloads).

The complete trip sequence — detection, decision, and opening — takes less than 1 ms in most industrial models. A conventional 10 A fuse may take 10–100 ms to blow at 15 A; during that time, a faulty load may have sustained additional damage or propagated the fault to other components.

Comparative trip speed: a short circuit on a 24 VDC circuit protected by a conventional 4 A fuse (type gG) generates a fault current of 20–50 A for 10–40 ms before opening. The same scenario with a correctly sized eFuse is resolved in <1 ms. The difference in energy dissipated in the load is an order of magnitude.

Operational advantages over conventional fuses

The eFuse’s superiority in industrial applications is not merely theoretical. It manifests across four concrete operational dimensions:

3.1 Instant diagnosis

Each eFuse channel has a status LED (green = OK, red = tripped) and, in models with IO-Link communication or a digital alarm signal, sends real-time status to a PLC or SCADA. The operator — or the supervisory system — knows within seconds which channel has failed without opening the panel. Average diagnosis time drops from 20–60 minutes to 2–5 minutes.

3.2 Reset without physical intervention

Configured in auto-reset mode, the eFuse closes the channel again automatically after a configurable wait time (typically 0.5–10 s). If the fault was transient — an inrush current spike, an electromagnetic interference event — the system recovers on its own. In manual reset mode, the operator presses a button with no need to replace any component.

3.3 Selective protection without complex coordination

The trip current is adjusted channel by channel, with a precision of 0.1–1 A depending on the model. There is no need to calculate coordination curves between cascaded fuses because the eFuse protects only its own channel and does not interfere with the others. A short circuit on channel 3 does not affect channel 4, even if both are powered by the same PSU.

3.4 Elimination of spare parts inventory

A single multichannel eFuse module protects 4 or 8 circuits with different loads. There are no spare fuses to manage, sort, or order urgently in the middle of the night during a plant breakdown. The module has a typical service life of 10+ years with no maintenance.

Reference figure: Murr Elektronik quantifies in its product documentation (2024) an average 60–80% reduction in fault diagnosis time for 24 VDC circuits when replacing conventional fuses with LED-signalling eFuses. For installations with 50+ circuits, this saving represents between 200 and 600 technician-hours per year in the most demanding cases.
Applications where the eFuse delivers the greatest value

Not all installations justify the investment in eFuses equally. The applications with the highest return are:

High-density circuit control panels: automation enclosures with 20 or more 24 VDC circuits powering different loads (sensors, valves, actuators, drives). Density justifies channel-by-channel selective protection.
Continuous production lines: in manufacturing where every minute of downtime has a direct economic cost (€200–2,000/hour depending on the sector), the eFuse’s automatic reset can restore the system without human intervention and without stopping production.
Data centres and server rooms: 24 VDC control circuits for IT equipment (PDUs, KVM switches, temperature sensors, UPS systems) demand maximum availability. The eFuse with alarm signal enables integration with Data Centre Infrastructure Management (DCIM) systems.
Food and beverage OEM machinery: environments with washdown cycles and high humidity where corrosion degrades conventional fuses prematurely. The eFuse, with no mechanical parts, is far more robust in these conditions.
Solar energy and storage systems: inverters and control systems in photovoltaic installations require protection of auxiliary low-voltage DC circuits (24 V) against faults that could compromise system availability for hours.
How to choose the right eFuse: five key parameters

Selecting an industrial eFuse requires evaluating five parameters in the order indicated:

The Premium PSU eFuse range

Premium PSU launches its first range of electronic fuses for DIN rail in 2026, designed specifically for the Spanish and Portuguese markets with local technical support in both languages. The range includes 1- and 4-channel modules for 24 VDC with per-channel adjustable current from 1 to 10 A and a rail width competitive with the best on the market.

Unlike higher-volume manufacturers, Premium PSU combines in a single offer the DIN Rail PSU for power supply and the eFuse for selective protection, with a unified warranty and a single technical-commercial contact for the complete panel. Technical documentation and application diagrams are fully available in Spanish.

Premium PSU is the only manufacturer simultaneously offering DIN Rail PSU + eFuse with native technical support in Spanish and Portuguese, with field presence in Spain and Portugal. Customers with ongoing projects can request evaluation samples at no charge by contacting their regional sales representative.

The electronic fuse is not an emerging technology; it has been present in the European industrial market for more than a decade and is available in the catalogues of the leading automation manufacturers. What is changing in 2025–2026 is the context: the digitalisation of control panels, the demand for greater production line availability, and the growth of new applications such as data centres and solar energy are transforming the eFuse from an interesting technical option into a standard component in modern projects.

For panel builders and OEMs still designing with conventional fuses, the question is not whether the eFuse is technically superior — it is, in virtually every relevant technical parameter. The question is whether the additional cost per channel is justified in their specific application. The next article in this series answers that question with real figures: a comparative 5-year TCO analysis for an industrial panel with 50 DC 24 V circuits.

Would you like to evaluate whether the eFuse is right for your next project? Contact the Premium PSU technical team: info@premiumpsu.com

PREMIUM PSU · Power supplies equipment and systems · www.premiumpsu.com

#	Parameter	Typical range	What to evaluate
1	Output current per channel	0.5 A — 20 A	Size to 125% of the load’s rated current. Leave headroom for motor and valve inrush current peaks.
2	Number of channels	1 / 2 / 4 / 8	In high-density panels, prioritise multichannel modules. An 8-channel module occupies 48–80 mm on DIN rail versus 8 individual fuse holders.
3	Rated input voltage	24 VDC / 48 VDC	Most eFuses on the market are optimised for 24 VDC. For 48 VDC, verify the model’s input voltage range.
4	Communication and diagnostics	None / LED / IO-Link / digital signal	For systems without PLC or SCADA: LED is sufficient. For automation integration: IO-Link or digital alarm signal with PLC output.
5	DIN rail width	6 – 90 mm / 4 channels	In space-constrained panels, width is decisive. The best models on the market achieve 6–8 mm per channel.

About Premium SA: Founded in Barcelona, Premium SA designs and manufactures
custom high-reliability power supplies and protection systems for industrial automation,
energy, and critical applications.
Over 40 years of experience in custom power electronics.www.premiumpsu.com ·
Contact our engineering team →

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Application Notes, Railway & Transportation, Sin categoría

Multilevel Inverters: NPC, FC, CHB and the Road to RDC-ML

Engineering Insight · Power Conversion Architecture

Multilevel Inverters: NPC, FC, CHB and the Road to RDC-MLI

From conventional two-level to neutral-point clamped, flying capacitor, cascaded H-bridge and reduced device count topologies — architectural synthesis for traction, grids and renewables

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Premium SA · Barcelona
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April 2026
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#PowerElectronics #MultilevelInverters #PremiumPSU

1981Year NPC Was Invented

<5%THD in 7+ Level CHB

1/2Per-switch Voltage Reduction

MWPower Range Where MLI Is Mandatory

Executive Summary

Multilevel inverters (MLI) represent the architectural evolution that made medium-voltage and high-power power electronics viable. Their fundamental principle — synthesising a stepped voltage waveform from several lower-voltage DC sources — solves simultaneously four problems that the conventional two-level inverter could not address: the blocking-voltage limit of commercial semiconductors, the harmonic distortion that penalises power quality, the dv/dt stress that destroys motor insulation, and the switching losses that prevent reaching efficiencies above 97% in the megawatt range.

The four structural advantages of MLI. (1) Divided blocking voltage — each semiconductor blocks only V/(m−1). (2) Reduced THD without sacrificing power — stepped waveform drops below 5% THD with no filter, complying with IEEE 519 directly. (3) Lower dv/dt — transitions occur between adjacent levels, reducing motor insulation stress by orders of magnitude. (4) High efficiency — semiconductors switch at low frequencies; overall efficiency approaches 98% in megawatt applications.

The Fundamental Principle — Additive Voltage Synthesis

A conventional two-level inverter has two possible output states per phase: +V/2 and −V/2. The transition between them is abrupt and requires a high switching frequency and a bulky output filter to approximate a sinusoid. Each switch must block the full DC-bus voltage, imposing a hard limit: above roughly 1700 V of bus, commercial IGBTs start running short on margin; above 3.3 kV, they simply do not exist as a single part.

The multilevel inverter solves this with an additive synthesis strategy: the output voltage is constructed by summing smaller contributions from intermediate DC-bus levels or independent sources. The resulting staircase waveform naturally approximates a sinusoid without high-frequency switching. The structural cost: more components than a two-level inverter — more switches, isolated gate drivers, clamping elements. Topology selection is the consequence of systematically analysing when that cost is justified.

The Three Classical Topologies

NPC — Neutral Point Clamped

Introduced by Nabae, Takahashi and Akagi in 1981, the NPC divides the DC bus into (m−1) levels through series capacitors and uses clamping diodes to connect intermediate nodes to switching points. The DC bus is single and shared by all three phases, minimising total capacitance. The main limitation is voltage imbalance in the intermediate DC-bus capacitors — manageable at m=3, but for m≥5 the control complexity becomes prohibitive. Practically all commercial NPC products are limited to three levels.

Aspect	Characteristic (m-level NPC)	Design Implication
Active switches	2(m−1) per phase	Linear growth with m
Clamping diodes	(m−1)(m−2) per phase	Quadratic — limits practical m to 3
DC sources	1 (single bus)	Architectural advantage over CHB
Dominant application	Three levels (m=3)	STATCOM/SVC, drives 690 V–4.16 kV, grid-tied PV

FC — Flying Capacitor

Proposed by Meynard and Foch in 1992, the FC replaces clamping diodes with floating capacitors holding intermediate voltages. Every switch blocks the same voltage, and redundancy of switching states allows active capacitor balancing through appropriate state selection each switching period — more manageable than the NPC. The disadvantage is quadratic capacitor growth (a 5-level FC requires 6 floating capacitors per phase) and a complex pre-charge startup routine. The FC dominates high-speed railway traction where per-cell modularity justifies the cost.

CHB — Cascaded H-Bridge

The CHB series-connects multiple complete single-phase H-bridges, each fed by an independent isolated DC source. The output voltage is the algebraic sum of each cell’s contribution. A CHB with N cells per phase produces 2N+1 levels. Its three structural advantages — pure modularity, absence of inter-capacitor balance issues, fault tolerance through cell bypass — make it the preferred topology when the application provides separate DC sources naturally (batteries, PV strings, multi-pulse transformers). Without that condition, NPC or FC are preferable.

Topology	Key Components	Main Advantage	Main Disadvantage
NPC	2(m−1) IGBTs + (m−1)(m−2) diodes	Single shared DC bus	Capacitor imbalance limits to m=3
FC	2(m−1) IGBTs + (m−1)(m−2)/2 cap.	Natural balance via redundant states	Quadratic capacitors; complex pre-charge
CHB	2(m−1) IGBTs + (m−1)/2 isolated sources	Pure modularity, fault tolerance	Needs isolated DC sources or multi-pulse transformer

Modulation Strategies

Multi-carrier SPWM and Phase-Shifted PWM (PS-PWM)

The natural extension of classical SPWM uses (m−1) triangular carriers per the Phase Disposition (PD), Phase Opposition Disposition (POD), or Alternative POD variants. PD minimises line-voltage THD and is preferred for NPC; POD minimises current THD. PS-PWM is specific to the CHB: each H-cell uses its own carrier, shifted 360°/N relative to the next, effectively multiplying the apparent output switching frequency by N without any individual switch switching faster — enabling very high efficiency at megawatt scale.

Selective Harmonic Elimination (SHE-PWM)

For very-high-power applications where switching losses dominate, SHE-PWM precomputes offline the switching angles that cancel specific harmonics (5th, 7th, 11th, 13th). For N pulses per quarter cycle, exactly N−1 harmonics can be eliminated. Switching losses drop to approximately 1% versus 3–4% for conventional PWM. The limitation is slow transient response and numerical instability beyond 5 levels.

Space Vector Modulation (SVM)

SVM operates on the αβ space of three-phase output voltages. Each switch-state combination corresponds to a vector, and the reference is synthesised as a linear combination of adjacent vectors. For a 3-level inverter: 27 vectors. For 5 levels: 125. For 7 levels: 343. Algorithmic complexity scales with m but SVM offers optimisable THD and high dynamic performance, making it the preferred strategy for FACTS and high-performance drives.

The Current Frontier — RDC-MLI and Asymmetric Topologies

Classical topologies share a scaling problem: switches grow with levels (a 7-level MLI requires 12 switches per phase; a 21-level one, 40). For 30-year reliability commitments, this escalation becomes unacceptable. Two research directions address it:

RDC-MLI (Reduced Device Count) architectures split the inverter into a level-generation stage (high frequency, determines magnitude) and a polarity-generation stage (fundamental frequency, decides sign). This separation reduces switching losses significantly. RDC-MLIs achieve 7 levels with 8–10 switches versus 12 for classical NPC/FC.

The asymmetric exponential trick. If CHB cells produce voltages in binary geometric progression (Vdc, 2·Vdc, 4·Vdc, 8·Vdc), a 4-cell inverter produces 31 levels instead of the symmetric 9 — with the same switch count. Ternary asymmetry (powers of 3) maximises level density (3^N theoretical levels) at the cost of control complexity. The trade-off: cells are no longer interchangeable, losing the classical CHB’s pure modularity.

Applications — Where MLI Is the Mandatory Solution

Railway Traction

High-speed traction (Talgo, Stadler, ICE) uses DC buses of 3 kV or 1.5 kV fed from the catenary, driving megawatt-scale motors. The three-level NPC has dominated this segment since the 1990s. The transition to SiC in some recent designs reopens the two-level debate — SiC allows faster switching without loss penalty — but the topology decision remains application-specific.

FACTS — STATCOM and SVC

A modern 100 MVAr substation STATCOM can have hundreds of H-cells per phase, each switching at a few hundred Hz, summing output voltages up to 33 kV without a step-up transformer. CHB modularity fits perfectly with qualified replicated H-cell manufacturing, and bypass fault tolerance keeps operation running with degraded performance — exactly what transmission operators require.

HVDC and Transmission

Modern VSC-HVDC uses the MMC (Modular Multilevel Converter) — an advanced CHB variant with hundreds of submodules per arm. European inter-country submarine interconnections (NorNed, Cobra Cable, Viking Link) use MMC with several hundred levels, achieving THD below 1% directly at the connection point. Cell redundancy makes per-cell failure irrelevant: with 400 cells per arm, the system tolerates dozens of failures without service loss.

Large-Scale Renewables and EV

PV plants use CHB naturally (each H-cell fed by a panel string); wind farms use three-level NPC for back-to-back converters; offshore wind increasingly uses MMC via HVDC. In automotive, the transition to 800 V battery buses in premium EVs (Porsche Taycan, Audi e-tron GT, Hyundai Ioniq 5/6) makes three-level inverters with 600–650 V SiC devices an increasingly attractive alternative to single-level designs with tight voltage margin.

Diagnosis and Troubleshooting

Observed Symptom	Probable Cause	Corrective Action
NPC capacitor imbalance	Deficient neutral-point control	Implement active control via redundant state selection
High THD at low modulation	Modulation index M < 0.5 in SPWM	Switch to SHE-PWM or third-harmonic injection
FC capacitor overvoltage	Active balance algorithm failure	Review redundant state selection; verify pre-charge
CHB cell current imbalance	Different battery SOC or DC sources	Adaptive asymmetric modulation to redistribute power
Elevated common-mode spikes	Modulation breaks 3-phase symmetry	Select PD-SPWM if NPC; review switching sequence
Saturated transient response (SHE)	Precomputed table out of regime	Hybrid SHE + SPWM in transients; revert to SHE in steady state

Topology Selection Matrix

Design Question	Favours NPC	Favours CHB
Single shared DC bus?	Yes — native to NPC	No — CHB needs isolated sources
Application provides separate DC sources?	No	Yes — batteries, panels, multi-pulse transformer
Levels required?	Up to 3	5 or more
Fault tolerance via cell bypass critical?	No	Yes
LRU maintenance modularity important?	Less	Yes — identical replaceable cells

The closing argument. Multilevel inverters are not an emerging technology — they have been the consolidated solution for medium-voltage, high-power power electronics for three decades. What continues evolving are the variants: three-level NPC consolidated, MMC dominating HVDC, RDC-MLI and asymmetrics as an active research frontier, SiC reopening the topology debate in the medium-power range. Topology selection is not a matter of taste: it is the consequence of a systematic analysis of bus voltage, waveform quality, DC source availability, modularity criticality, and maintainability horizon. Premium SA applies this analysis at the D2W gate of every new programme — because the right topology, well-chosen modulation, and rigorous thermal control are what differentiates a megawatt converter that meets 30 years of service from one that fails at five.

About Premium PSU

Premium SA is a Barcelona-based specialist in custom power electronic converters for railway, industrial, defence, and energy applications. Over 900 standard designs, 40+ years of operational experience, supplying converters from 50 W to 72 kW.

www.premiumpsu.com · info@premiumpsu.com · +34 932 232 685 · Born in Barcelona, Powering the World

Premium SA — Born in Barcelona, Powering the World

Need a custom power supply for your critical application?

Our engineering team designs custom power electronics solutions for railway, defence, energy and industrial applications.

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Case Studies by industry, Case Studies by product, Custom solutions, DC/DC converters

Case Study Ensuring critical lubrication in wind turbines during grid-Out scenarios

A CBS-10K HV DC/DC–based approach to protect high-value mechanical assets
Read more

Case Studies by industry, Case Studies by product, Custom solutions, Energy

People Counting in Demanding Environments: Reliable Power for Accurate Vision

Premium PSU continues to invest in specialized power electronics for embedded AI, smart counting, and vision systems in transport. The CLS-120 is a clear example of how robust power design can make the difference in projects where precision, integration, and reliability are critical.

Power electronics enabling the future of smart mobility

With the growing automation of public transport and railway networks, embedded AI applications are becoming standard. In this context, Premium PSU, in collaboration with its partner Relec (Martin Bull, Business Development Manager), worked with a transport technology provider to deliver a reliable people counting solution in a high-traffic environment.

One of the main challenges was the lack of an efficient inverter that could precisely control the speed of the motorized fans, avoiding current surges during startup and ensuring more stable operation.

The Challenge: Clean, Stable Power for AI Vision in Harsh Conditions

The goal was clear: to provide stable and safe power to embedded vision sensors with non-standard DC input, capable of operating in an environment filled with:

Electrical noise
Constant vibrations
Fluctuating temperatures

People counting systems must function flawlessly, even when thousands of passengers pass through in just a few minutes. For accurate and consistent performance, these sensors require a power solution that is:

Compact and easy to integrate
Highly immune to electromagnetic interference (EMI)
Capable of converting non-standard voltages
Protected against overloads and network disturbances

The Solution: Premium PSU’s CLS-120 converter

The CLS-120 was the ideal fit — a robust DC/DC converter designed for harsh transport environments. Its key features include:

Wide non-standard input range, compatible with diverse system architectures
Stabilized output to protect sensitive AI hardware
High EMI immunity and integrated noise filtering
Compact form factor, ideal for embedded or cabin integration
Full compliance with major railway and transport standards

Real-world application: AI-based counting at an international airport and railway stations.

This solution was deployed in critical high-flow passenger areas — including a major European international airport and busy railway stations — where the environment posed multiple challenges:

Continuous heavy passenger traffic
Potential micro-cuts or power fluctuations
Limited space for additional equipment

Despite these conditions, the CLS-120 enabled the embedded vision system to operate with over 98% counting accuracy, even during peak hours.

Expert Insight

“Adapting the power supply to such a constrained environment — like a train carriage — was a real challenge. We needed highly robust electronics: immune to noise, yet compact and easily integrable. After several validation rounds, the CLS-120 helped us deliver a tested, proven solution in just a few weeks.”
— Francisco Mauro, Project Manager, Premium PSU

Customer Feedback

“Integrating the CLS-120 into our embedded counting system fully resolved the electrical noise issues we had been experiencing in high-traffic environments. The converter delivered a stable response to transient spikes and integrated seamlessly into our architecture — with no compromise in space or performance.”

A Reliable solution for smart transport

Broader application scope: Beyond Airports and Railways

While this case focused on a high-traffic transport environment, the CLS-120 converter is equally suited to other demanding sectors where embedded vision systems are critical. From maritime transport (ferries and cruise ships) requiring robust, vibration-resistant power supplies, to smart infrastructure such as stadiums, metro stations, and large public venues, the need for stable DC power is universal. Additionally, industries like retail analytics, building automation, and healthcare facilities increasingly deploy AI-powered people counting and monitoring systems. In each of these contexts, the CLS-120 provides compact, EMI-immune, and highly reliable power — making it a versatile solution wherever accuracy, uptime, and safety are non-negotiable.

Case Studies by industry, Case Studies by product, Custom solutions

Efficient and Robust Power Supply for Refrigeration Systems from High-Voltage Batteries

In a world where sustainability and energy efficiency are no longer optional, urban refrigerated transport is undergoing a major transformation. Every day, thousands of refrigerated vans and trucks deliver fresh goods to supermarkets, restaurants, hospitals, and homes across Europe. And on every route, there’s one non-negotiable requirement: preserving the cold chain. Read more

Case Studies by industry, Case Studies by product, Custom solutions, Railway & Transportation

An Electrifying Challenge in the Mining Industry

Prairie Machine / Rokion, a leader in electric vehicles for mining, faced a critical mission: ensuring a robust power source for their electric trucks. It was then that Premium PSU became the ideal strategic partner, taking reliability and power to the next level.

Case Studies by industry, Case Studies by product, Custom solutions, Energy

The Solution for HVAC Modernisation on European Trains

A leading manufacturer in the sector faced the challenge of improving the control of its motorized fans without compromising system stability or violating strict railway standards. By implementing the ODX-4500 inverter from Premium PSU, they optimized energy consumption, reduced mechanical failures, and ensured seamless integration with their existing infrastructure. Read more

Case Studies by industry, Case Studies by product, Custom solutions, Energy

Power transformation chargers for energy sector

In an increasingly environmentally conscious world, leading companies are seeking innovative solutions to drive the transition towards a greener energy future. Iberdrola, globally recognized as one of the foremost companies in clean energy, grids, and storage, has partnered with us to develop a series of groundbreaking products that are redefining modern energy infrastructure.

Our collaboration with Iberdrola has resulted in the creation of two innovative products: the NP-0821 and NP-0822 power transformation chargers. These devices are designed to provide uninterrupted power supply and are instrumental in integrating new elements in low-voltage electrification, as well as adding new functionalities for the digitization of the power grid.

Enhanced Functionality

The new equipment boasts advanced algorithms that facilitate the monitoring and control of power supply assets in the transformation centers, all while ensuring strict compliance with the client’s cybersecurity requirements. This equips the network with greater adaptability to address any power supply issues that may arise.

Key Features

The key characteristics of these devices include:

NP-0821

Uninterruptible power supply system for 48V LiFePO4 batteries

2 outputs of 500W (750W for 10s) and 250W (500W for 10s) isolated at 10kV from each other

2 or 3-state battery charging

Local monitoring with 3 LEDs

Remote monitoring with 4 alarm relays

Configurable charging parameters

Alarm signaling through potential free relays

2 Ethernet ports for local and remote configuration and monitoring

1 CAN port for communication with BMS

Integrated web server

Battery connection via solid-state relay

10kVac input-output isolation

NP-0822

Uninterruptible power supply system for multiple types of 12V batteries (lead acid, lithium, etc.)

2 or 3-state battery charging

1 output of 12V 200W (400W for 10s) and 2 independent 48V outputs for maneuver (200W / 300W for 10s) and control (60W) with a peak of 400W for 10s

Local monitoring with 3 LEDs

Remote monitoring with 4 alarm relays

Configurable charging parameters

Alarm signaling via potential free relays

2 Ethernet ports for configuration and remote monitoring

1 CAN port for communication with BMS

Integrated web server

Battery connection via solid-state relay

2kVac input-output isolation

The development of these innovative power transformation chargers signifies our commitment to pushing the boundaries of technological advancement in the field of sustainable energy and power grid management. By delivering solutions that cater to the evolving needs of our clients, we continue to pave the way for a more efficient and secure power infrastructure.