Toroidal Transformers
A toroidal transformer is an electro-magnetic device used to transfer electrical energy away from one electric circuit and toward another, without changing the frequency, by the principles of electromagnetic induction. Toroidal transformers are donut-shaped transformers which are highly space efficient and excellent for reducing electromagnetic interference. Offering quiet, efficient operation, toroidal transformers have very low stray magnetic fields because they have almost no air gaps. Toroidal transformers are the smallest-sized transformers in regards to both weight and volume, which works to the advantage of toroidal transformer manufacturers because they can be easily incorporated into any power source application that can accommodate its shape. Industries that benefit from toroid transformers include electronics, aerospace, musical instrument, medical, private security, meteorology and transportation. Used as transformers in main power supplies, additional applications for toroid power transformers include audio amplifiers, battery chargers, induction loop equipment, household appliances, motor drives, cranes, lighting and medical devices. Toroidal transformers are also used as inductors in low frequency transmitters and receivers.
The central part of a toroidal transformer is its donut-shaped core. The core is constructed from grain-oriented silicon-iron or permalloy which is slit to form a steel strip. The steel strip is then wound into a coil, made from powdered iron, or ferrite. The construction the strip ensures that all of the molecules are aligned with the direction of flux, or the rate of flow of energy across a given surface, and increases the capacity for magnetic induction. Since the core is closed and ring-shaped, air gaps are eliminated that are inherent in other cores. The cross-section of the core is typically either square or rectangular, but can also be cylindrical in pricier cores. The primary and secondary coils are wound in a densely concentrated manner to ensure that the entirety of the core's surface is covered. The two coils are linked by a magnetic field, resulting from electromagnetic induction, and act as conductors. When the primary coil receives AC voltage, this produces a varying magnetic field of voltage surrounding the conductor; the magnetic field activates the secondary conductor coil. This results in the toroid transformers changing the voltage and transferring electrical energy, ideally with the least amount of energy loss. The design of toroid transformers prevents energy loss by confining the magnetic flux in the core. There are two directions of fluxes in the toroid magnetic field: poloidal flux; which threads the hole in the center of the torus; and toroidal flux, which is parallel to the core of the torus.