The performance of a toroidal transformer may be further optimized with an O-Core.

The grain oriented silicon steel properties are the same as in our conventional toroidal cores giving the O-Core Transformers the same electrical benefits and can be used in designs for the same applications.

O-Cores are wound from a steel strip, which is continuously pointed towards each end to produce a circular cross section. The circumference of a circle is about 12% less than that of a square with same area and 18% less than a rectangle with the same area and a height to width ratio of 2:1 as in the most popular conventional toroidal transformer.

Since O-Cores have no sharp edges they require less insulation and can be wound with less fill factor resulting in a lighter and smaller transformer than the conventional toroid. Due to a slower core production process and a higher scrap factor the O-Cores are more expensive than conventional toroidal transformers.