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Introduction of toroidal transformer

There is no denying that toroidal transformers are the high performers among the various types of transformers available in the market though the toroidal transformers are the smallest in physical and lowest in weight. Toroidal transformers offer many advantages over standard laminated power transformers. Toroidals provide quiet, efficient operation with very low stray magnetic fields. Their small size and low weight make them ideal to design into any application.

The other features of toroidal transformers are less leakage inductance and lower electromagnetic interference (EMI). Besides, their windings generally cool better because of the proportionally larger surface area. A totally wound toroidal transformer has a high degree of symmetry. Its geometry leads to near complete magnetic field cancellation outside of its coil, hence the toroidal transformer has less leakage inductance and less EMI when compared against other transformers of equal power rating.

Since toroidal cores are constructed of a continuously wound ribbon, there is virtually no air gap. The windings are evenly wrapped over the entire core allowing the transformer to operate at a higher flux density than in standard transformers. Toroidal coils reduce resistance, due to the larger diameter and smaller number of windings. The magnetic flux in a toroid is confined to the core, preventing its energy from being absorbed by nearby objects.

While the cross-sectional area of the toroidal core must be held constant, the height and diameter can be varied to meet package constraints. The functional optimum ratio of diameter to height is 2:1. A 3:1 ratio may be used in applications where a very low profile is required. And if a minimum footprint is required an aspect ratio of 1.5:1 may be considered.

But toroidal transformers are not without its disadvantages. Toroidal transformers can be used in any electronic transformer application that can accommodate its shape. Although usable, toroidal transformers are not always practical for some applications. Gapped toroidal transformers usually require that the gap be filled with some type of insulating material to facilitate the winding process. This adds to expense and involves extra work. Mounting a toroidal transformer flat on the board may take up too much precious board area. Some applications also have restricted height so the toroid cannot be mounted vertically.

Experts say that toroidal transformers with a round core cross section are more efficient than toroidal transformers with a rectangular cross section. The round cross section also gives a shorter turn length per unit of cross sectional area, hence lower winding resistances. The toroidal transformer also has better winding to winding magnetic coupling because of its toroidal shape.

Toroidal transformer cores come in different materials like silicon steel, nickel iron, moly-permalloy powder, iron powdered, amorphous, ferrites, and others. Silicon steel and nickel iron are available as tape wound cores or laminated pieces. Non-magnetic toroids are also available to make air core toroidal transformers.

There are suppliers in the market who provide custom solutions to all types of requirements particularly if you need more than a prepackaged transformer for any unique application. Most suppliers have technical personnel to guide you in toroidal mounting, leads, terminations, and safety protection and recognition.