Why Are Toroidal Transformers Known As Doughnuts?

Toroidal transformers are used for a whole range of purposes, from audio toroidal transformers to simple yet effective transformers designed for common use in applications where space-efficiency is key.

Why Are Toroidal Transformers Known As Doughnuts?

But why is this particular type of transformer commonly referred to as a ‘doughnut’? The reason is a surprisingly simple one, and it all boils down to the fact the two objects have a certain resemblance.

What Is a Toroid?

A toroid is a shape. It’s a round shape with a hole in the middle – the kind of shape you get if you take a length of tubing or rod and join the ends so that it runs in a continuous circle. In other words, it is a shape much like that of a doughnut. Something shaped like a toroid is described as ‘toroidal’.

Toroidal transformers are so called simply because they have this shape, at least internally, and this is where they get the nickname of doughnuts. A doughnut is probably the most familiar toroid, so most people’s first thought on seeing a toroid is ‘that’s doughnut-shaped’. There are various types, sizes and power ratings of toroidal transformers available from the companies such as http://sigatransformers.co.uk/, but they all have this doughnut-like shape.

Why Are They This Shape?

All transformers – or at least all kinds in common use – work on very similar principles, and as such they all have many components in common. The main components in question are a magnetic core surrounded by a coil of copper electrical wire.

However, there are various shapes and configurations in which these components can be put. One of these is the toroid. Effectively, this is a fairly long cylindrical transformer looped around into a circle, as this is more space-efficient and practical than creating a similar set-up as a straight rod.

What Are the Advantages of Toroidal Transformers?

Each type of transformer has its own unique advantages and attributes. In the case of toroidal ones, the key advantage in most cases is size. They are smaller and more lightweight than other equivalent transformers of different types.

Because they use magnetism, transformers also create an external magnetic field. For certain technical reasons, this field is weaker with toroidal transformers than with many other types, which is another advantage where interference is a concern.