The no-load loss of the transformer includes iron loss and copper loss, copper loss mainly refers to the loss caused when the primary current flows through the primary winding, and the iron loss is composed of hysteresis loss and eddy current loss. Reducing no-load losses requires a reduction in magnetic flux density, which results in an increase in the weight of the permeable material. Either use high-permeability, low-loss permeable materials, or use thinner permeable materials. As a result, the cost of transformers increases.
The no-load loss of a transformer is the sum of the iron loss and copper loss of the transformer, and the iron loss depends on the voltage and is independent of the load. The copper loss is related to the load current, and the higher the load current, the greater the copper loss.
After the transformer has an air gap, its relative permeability region is linear, and the size of the relative permeability mainly depends on the size of the air gap, and the material of the core has little relationship. Different lamination processes have different sizes of air gaps, small relative permeability, low L value, and large no-load current and loss. The air gap in the magnetic circuit of the coiled core (no seam in the middle) is zero, the relative permeability is high, the L value is high, and the no-load current and loss are small.