No-load losses are the electrical losses a transformer incurs simply from having operating voltage applied – even without any load connected. Because transformers are often permanently connected to the grid for decades, these losses add up to substantial amounts of energy. Consistently reducing no-load losses through high-quality core materials is therefore one of the most effective levers for sustainably improving the energy efficiency of entire distribution grids. Given that distribution transformers are connected to the grid around the clock, no-load losses represent a significant energy cost over the decades in every grid area.
What causes no-load losses?
They consist of two main components: hysteresis losses and eddy current losses. Both occur in the iron core due to the continuous remagnetization caused by the alternating current. Hysteresis losses depend on the core material, while eddy current losses depend on the thickness of the laminations and their electrical resistivity. High-quality grain-oriented electrical steel, and amorphous cores in particular, significantly reduce both loss components. No-load losses are independent of loading and occur around the clock.
Key Characteristics at a Glance
- Main components: hysteresis losses and eddy current losses
- Independent of load – occur 24/7
- Reduced through high-quality electrical steel or amorphous cores
- Specific values given in watts per kg of core material
- Regulated by the EU Ecodesign Directive (EU 548/2014)
- Grain-oriented electrical steel as the standard solution
- Permanent Domain Refining (PDR) reduces losses further
Frequently Asked Questions
What are typical no-load losses for a modern distribution transformer?
A 630 kVA distribution transformer compliant with EU Ecodesign Tier 2 has no-load losses of around 580 W. Over a year of continuous operation, that amounts to around 5,080 kWh – roughly the consumption of an average household. With amorphous cores, this figure can be reduced by 60 to 70 percent.
Is investing in a low-loss transformer worthwhile?
For units operated continuously, the higher acquisition costs are often recovered within 5 to 10 years. Over the total service life of 30 to 40 years, the resulting savings usually reach several times the difference in acquisition cost – even at moderate electricity prices.
How are no-load losses measured?
In the factory, the transformer’s secondary side is left open and rated voltage is applied to the primary side. The active power then drawn corresponds to the no-load losses. The measurement is carried out according to IEC 60076 and is part of every routine test.
How much do low-loss transformers save in a typical grid area?
Consistently modernizing distribution transformers in a mid-sized grid area can save several gigawatt-hours annually. Over their service life, this corresponds to a reduction of thousands of tonnes of CO₂ – a substantial contribution to the energy transition without any loss of comfort for consumers.
What standards regulate permissible no-load losses?
EU Regulation 548/2014 (Ecodesign Tier 2) is decisive, setting binding maximum values for every power class of distribution and power transformers. Similar standards apply internationally, such as DOE requirements in the USA. These regulations are driving the adoption of higher-quality core materials.
Would you like to reduce the no-load losses in your distribution grid? We supply highly efficient transformers with conventional or amorphous cores – get in touch with our specialists.