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Magnetics for renewable energy conversion

MPPT stages, grid tie inverters, battery energy storage and electrolyser rectifiers. In this sector a point of efficiency is not a specification line, it is revenue compounded over twenty years, and that changes which trade you should be making in the magnetics.

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Where the magnetics sit

The stages, and what goes in each one.

MPPT and boost

Interleaved boost from the string voltage, often in 1500 V DC systems.

The magnetic: Boost inductor working with heavy DC bias plus superimposed ripple. Inductance against DC bias is the curve that matters, and we measure and report it.

Inverter output filter

Two level, three level T-type or NPC stages feeding the grid.

The magnetic: LCL filter inductors, where core loss is set by the switching ripple and copper loss by the fundamental. The two want different constructions and the design has to settle that.

Galvanic isolation

LLC or dual active bridge stages where the architecture calls for isolation.

The magnetic: Isolation transformer designed for the isolation class the grid code and the safety standard actually require.

Grid EMC

Conducted emissions against the limit line for the installation class.

The magnetic: Common mode chokes on the DC string side and the AC side, sized from your measured scan.

What decides it

What actually drives the design here.

Efficiency is money

At twenty year service life, half a point of loss in a magnetic is a real number on the plant model. That justifies litz where a catalog part would use solid wire, and it justifies a larger core where a smaller one would have passed.

1500 V DC

System voltage sets creepage, clearance and the insulation system before anything else gets decided.

DC bias, not just ripple

A boost inductor spends its life biased. Designing to the small signal inductance and finding the saturation knee in the field is the classic way to lose a summer.

Outdoors

Temperature swing, humidity and altitude all belong in the specification, because they change the insulation and the thermal design.

The shape of it

Standards, range and typical parts.

Safety isolation
EN and IEC isolation requirements for the installation class
Measured and reported
Inductance against DC bias, core and winding losses, temperature rise under your waveform
Materials
Ferrite, nanocrystalline, amorphous and powder, chosen for the ripple and the bias
Typical parts
Boost inductors, LCL filter inductors, isolation transformers, DC and AC line chokes

Questions

Renewable energy, the usual questions.

How do you size a boost inductor for a 1500 V string?
From the ripple current you can accept, the switching frequency, and the DC bias at the worst case operating point. The core material and the gap strategy follow from those, and the system voltage sets the insulation. We give you inductance against DC bias as a curve, not a single number.
Ferrite, nanocrystalline or powder for a filter inductor?
It depends on where the loss is. Iron powder has a soft saturation knee and tolerates bias well but has higher core loss. Ferrite has low loss but saturates hard. Nanocrystalline gives high permeability and good high frequency behaviour at a cost. We size it both ways when the choice is close and show you the loss split.
Can you improve the efficiency of an inductor we already use?
Often, yes. Send the part or the drawing and the operating point. Reverse engineering an existing magnetic and rebuilding it for your actual waveform is work we do routinely, and the answer sometimes is that the part you have is already right.
Do you supply for electrolyser rectifiers?
Yes. High current, low voltage rectification puts the design pressure on the winding rather than the core: conduction loss, current sharing and the thermal path dominate. Edge wound flat wire and foil both come up here.
What do you measure before shipping?
Inductance, inductance against DC bias, DC resistance, hipot, and temperature rise under the customer waveform. Those values arrive with the part, on its test report.

Start here

Send us your renewable energy spec.

A schematic and a waveform are enough to start. You get a first design proposal with estimated losses, the inductances, the dimensions and the expected hotspot temperature, before you have spent anything.

Send us your spec

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