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Advantages of toroidal vs EI and R-core transformers

Toroidal transformers - best choice for your audio application

As an important part in a chain of electronic components, making a choice of a transformer will probably open a box of questions. The following informations shall support to get basic informations about common used transformer constructions in audio applications, further about their differences. And because we're actually often asked, why we offer toroidal transformers, MPAudio also hopes to answer this question, describing the main advantages of toroidal transformers vs other transformer constructions. In some aspects our transformers differ from "usual" toroidal transformers, as they are designed to meet necessary characteristics for sensitive audio setups. This differences are specifically mentioned in the following description as well:

Electrical efficiency

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. One of the benefits is, that toroidal transformers offer very stable output voltage, resulting in less voltage drop also during high loads. 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.

Efficiency vs Load of MPAudio Transformers