The variable toroidal transformer is a special type of transformer whose core is manufactured in the form of a ring. The toroidal core is made of soft iron or special ferrites. In a toroidal transformer, the windings are wound over the toroidal core, electrically insulated. The windings of enameled copper wire are evenly distributed over the entire toroidal core, which is why 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 virtually non-existent due to the shape of the core. This can be demonstrated by the low no-load current and an almost vertical hysteresis curve. However, toroidal transformers generate very high current peaks when they are switched on, which is why an inrush current limiter is advantageous for toroidal transformers .