Toroidal Transformers

Toroidal Transformers are transformers with a core that is constructed in the form of a toroid.  A toroid is a geometric shape which resembles a doughnut. 

This form of transformer construction has the advantage of having a higher efficiency in comparison with an ordinary transformer.  They also have lesser size and weight.  These transformers are widely used in audio amplifier circuits as they do not have very less mechanical hum. 

These transformers have very low leakage flux as the core, being circular eliminates airgaps.  Another advantage of the toroidal transformer is the low Electromagnetic Interference.  Since the windings are located outside the core, heat dissipation is also easier. 

An important precaution should be taken while fastening the Toroidal Transformer.  The fastening bolt, which usually passes through the centre of the toroidal transformer should only be fastened at one end.  If the bolt is fastened at two ends to metallic objects.  It may act as a secondary causing a huge current in the primary and can even cause fire as the bolts melts under the high induced current. 

The downside of Toroidal Transformers is its high manufacturing cost.  Hence, they are usually made only upto a few kVA. 

Toroidal Current transformers are widely used for low and medium voltage applications.