Two components make the whole transformer: a magnetic core and windings. Their materials determine the two loss families you will pay for thirty years, and that the Tier 2 regulation caps.
The core is a stack of grain-oriented silicon-steel laminations, insulated from each other and assembled with staggered ("step-lap") joints to smooth the flux path. Its quality determines the iron losses, known as no-load losses (P₀), present from energisation, around the clock, whether the unit delivers or not. Over thirty years of operation that line weighs heavily: it is precisely what Ecodesign Tier 2 caps first. The principle behind all this is in how a transformer works.
Amorphous metal (a non-crystalline alloy) cuts no-load losses spectacularly, commonly in the order of 60 to 70 % versus classic laminations. The counterpart: a somewhat bulkier unit, costlier to buy, sometimes noisier. It is justified where the transformer stays energised permanently at a low average load, public distribution, lightly loaded sites, where no-load losses dominate the balance. The calculation is case by case: a total-cost-of-ownership trade-off, not a reflex.
Around the core, two windings per phase: the LV (often foil) and the MV (flat or round wire, in layers or discs). Their resistance creates the load losses (Pₖ), proportional to the square of the current: at half load they fall to a quarter. The copper / aluminium choice is a classic trade-off: copper conducts better and ages better at equal size; aluminium, lighter and cheaper, requires larger cross-sections. Both are done cleanly; the essential is that the guaranteed losses respect Tier 2, which we specify in both cases.
Regulation (EU) 548/2014 caps both (Tier 2 level since July 2021): the legal floor. Depending on your load profile, aiming better than Tier 2 on one family or the other can pay back within a few years: the "Higher efficiency" option of our configurator, whose arithmetic also drives the price factors.
Orders of magnitude given as guidance; exact guaranteed losses appear on the quotation and on each unit's individual test report (EN 60076-1).
By the load profile. If the transformer stays energised permanently at a low average load, no-load losses dominate and amorphous pays back. If the unit works hard and long, load losses dominate and classic grain-oriented steel with good windings is the better bet. It is a total-cost calculation, case by case.
Both are done properly. Copper conducts better and ages better at equal size; aluminium is lighter and cheaper but needs larger cross-sections. What matters is that the guaranteed losses respect Tier 2, which we specify in both cases.
The magnetic hum comes from the core vibrating with the flux. Working the core at a lower flux density reduces both the hum and the iron losses, which is why low-loss machines are often the quieter ones.
An assembly of the core laminations with staggered joints, smoothing the flux path at the corners. It reduces no-load losses and noise compared with straight joints.