TRANSFORMER EN UN FULL
A failure of the isolation of the windings of an autotransformer can result in full input voltage applied to the output. If one of the center-taps is used for the ground, then the autotransformer can be used as a balun to convert a balanced line (connected to the two end taps) to an unbalanced line (the side with the ground).Īn autotransformer does not provide electrical isolation between its windings as an ordinary transformer does if the neutral side of the input is not at ground voltage, the neutral side of the output will not be either. Depending on the application, that portion of the winding used solely in the higher-voltage (lower current) portion may be wound with wire of a smaller gauge, though the entire winding is directly connected. For example, connecting the load between the middle of the winding and the common terminal end of the winding of the autotransformer will result in the output load voltage being 50% of the primary voltage. For a step-up transformer, the subscripts in the above equations are reversed where, in this situation, N2 and V2 are greater than N1 and V1, respective.Īs in a two-winding transformer, the ratio of secondary to primary voltages is equal to the ratio of the number of turns of the winding they connect to. In a step-up transformer, conversely, the load is attached across the full winding while the source is connected to a tap across a portion of the winding. In a step-down transformer the source is usually connected across the entire winding while the load is connected by a tap across only a portion of the winding. Different taps on the winding correspond to different voltages, measured from the common end. The other end of the source and load are connected to taps along the winding. One end of the winding is usually connected in common to both the voltage source and the electrical load. However the voltage and current ratio of autotransformers can be formulated the same as other two-winding transformers: V 1 V 2 = N 1 N 2 = a
TRANSFORMER EN UN SERIES
In an autotransformer, part of the output current flows directly from the input to the output (through the series section), and only part is transferred inductively (through the common section), allowing a smaller, lighter, cheaper core to be used as well as requiring only a single winding.
![transformer en un transformer en un](https://content.instructables.com/ORIG/FOT/G0W5/J6CG2K5J/FOTG0W5J6CG2K5J.png)
Since the volts-per-turn is the same in both windings, each develops a voltage in proportion to its number of turns. The secondary voltage is taken from two terminals, one terminal of which is usually in common with a primary voltage terminal. The primary voltage is applied across two of the terminals. The portion of the winding not shared by both the primary and secondary can be, and is often, referred to as the "Series Section". The portion of the winding shared by both the primary and secondary can be, and is often, referred to as the "Common Section". It is a transformer in which the primary and secondary coils have part of their turns in common.
![transformer en un transformer en un](https://bbts1.azureedge.net/images/p/full/2019/11/507fefe0-39ac-4b10-ba43-ae628c63a74d.jpg)
Since part of the winding does "double duty", autotransformers have the advantages of often being smaller, lighter, and cheaper than typical dual-winding transformers, but the disadvantage of not providing electrical isolation between primary and secondary circuits. The autotransformer winding has at least three taps where electrical connections are made. In contrast, an ordinary transformer has separate primary and secondary windings which have no metallic conducting path between them. In an autotransformer, portions of the same winding act as both the primary winding and secondary winding sides of the transformer. The " auto" (Greek for "self") prefix refers to the single coil acting alone, not to any kind of automatic mechanism. Single-phase tapped autotransformer with an output voltage range of 40%–115% of inputĪn autotransformer is an electrical transformer with only one winding.