Updated: Nov 10, 2020
High efficiency and performance of toroidal transformers are obtained mainly thanks to the use of cores made of silicon steel with oriented grain (CRGO - cold rolled grain oriented) with the right shape. The core is coiled under a large tension - into the shape of a clock spring - with a continuous, unbroken strip of material without an air gap. The effect of setting the molecular structure of the material in magnetic direction is obtained by stress relief annealing. For comparison it is determined that cores composed of EI-cut shaped bodies have about 40% of grains provided in the wrong direction.
Symmetrical distribution of transformer turns around the entire perimeter of the toroidal core without an air gap gives the opportunity to obtain a larger magnetic flux. Typical values of the magnetic flux of the EI-transformer is 12-14 kG, while for toroidal transformers values of 16-18 kg are achieved. It should be remembered here, that in a toroidal transformer the magnetic flux is oriented in a direction consistent with the grain system of the material.
Thanks to these unique properties it is possible to obtain extremely high electrical efficiency. The average efficiency of toroidal transformers is 95%, while for high powers of 20kVA, even efficiency up to 98% is achieved. Compared to classic constructions these values are higher by 14% on average.
The graph below presents typical efficiency values of classic and toroidal transformers
as a function of load.
Low Noise Level
The most important cause of mechanical noise during transformer operation is the so-called magnetostriction phenomenon. This phenomenon consists of deformations (vibrations) of ferromagnetic materials under the influence of an alternating magnetic field. This undesirable phenomenon can be significantly reduced by using toroidal cores in transformer design: Windings tightly wrapped, no air gap and the use of modern impregnants makes it possible to obtain even eight times lower loise level, when working under load.
Low magnetic field emission
Due to its unique design and efficiency, the toroidal transformer is characterized by
90% reduced magnetic field emission. Transformer winding exceptionally exactly covering the core act as a shielding element and focusing the magnetic field there, where it is optimally used to transform primary energy into secondary energy transformer. This feature allows the use of toroidal transformers exceptionally sensitive electronic devices such as low level signal amplifiers or medical devices.
Low power loss during unloaded operation
A toroidal transformer requires significantly less electric resources when operating without load. The energy consumed in this state is 16x smaller compared to classic shape transformers. This results in gigantic energy savings for devices with discontinuous performance characteristics - such as transformers for industrial machines.
For example, the equivalent of a classic toroidal with 100W resting power based on a toroidal transformer will consume about 6W only. The chart below shows a schematic comparison of electric energy consumption by both types of transformers.
Another advantage resulting from the design of the toroidal transformer is the ability to adapt the dimensions of the transformer to customer needs. The toroidal core can be modified in three dimensions: outer diameter, inner diameter and height while maintaining the same cross-sectional area of the magnetic core. This makes it possible to use toroids where transformers built in EI shape do not fit.
Minimization of dimensions and material consumption
The easiest observable difference between toroidal and shaped transformers
are their dimensions. Toroids are up to 50% smaller and need 30% less production materials in average. It should be remembered that both CRGO steel and high purity copper are raw and very expensive materials, and their processing requires a lot of energy.