For voltages used with the purpose of powering the various devices used in electrical transformers and autotransformers. Due to the similarity of the names of the inexperienced user is difficult to assess the differences between them, especially since the principle of operation of the electrical equipment is very similar. However, their function and internal structure, they differ significantly from one another.
What is transformer?
Transformer - a simple technical device, which has in its composition of two or more coils placed on a common core or the yoke (pictured below).
By this arrangement of the windings are inductively interconnected, as are in general electromagnetic field. According to Faraday's law when activating one of the coils (when a voltage in the coils due to its leakage AC) to the other induced secondary voltage. It is in phase and frequency to the original signal, but it has a different amplitude.
Note: The magnitude of the induced voltage depends on the ratio of the number of turns of wire in the primary and secondary coils.
The feature of this device design is that both windings of the transformer have no electrical connection (electrically isolated).
Operating principle
Assume that the primary winding of the transformer device is supplied mains voltage U1 amplitude of 220 volts (or any other value). Thus flowing through it alternating current generate magnetic flux which permeates the core and according to Faraday's law the secondary winding will bring a certain EMF U2 (pictured below).
Additional Information: The principle of the interaction of the transformer coils based on the known phenomenon of electromagnetic induction.
The magnitude of the output voltage depends on its structural characteristics (the ratio of the primary windings N1 and the secondary windings N2 or transformation coefficient).
autotransformer
In auto-transformer in fact only one winding, having a plurality of electrical outlets. That is, in this device the primary and secondary coils are electrically connected to each other (decoupling No power) In this and shows the main difference from the conventional transformer (the difference - in the photo below).
The winding device has at least three terminals, due to the connection to which can obtain desired voltage amplitude.
Important!Because there is no galvanic isolation autotransformer - mains voltage of 220 volts could be applied to the output of the circuit.
It is fraught with combustion devices connected to the output, as well as a threat to working with user loads. Autotransformer devices are available in two versions: they are fixed or variable volume. The latter type are well-known products such as laboratory autotransformers (Latro).