Variable Toroidal Transformer

The variable toroidal transformer is a type of transformer whose core is made in the form of a toroid. The toroidal core is made of soft iron or special ceramic ferrites. In a toroidal transformer, the windings are wound over the toroid, electrically insulated. The turns of copper wire are evenly distributed over the entire toroid, therefore the magnetic leakage flux in a toroidal transformer with good magnetic coupling is distributed over the entire core. The magnetic resistance in the toroidal transformer, caused by the smallest possible air gap in the core, is almost non-existent due to the shape of the core. This can be proven by the low no-load current and an almost vertical hysteresis curve. However, toroidal transformers generate very high current peaks when switched on, which is why an inrush current limiter is advantageous for toroidal transformers.