Auto transformers

Auto transformers

Auto transformers;

An automotive vehicle electrical device could be a electrical device that has a part of its winding common to the first and secondary circuits. Figure 20.14(a) shows the circuit for a double-wound electrical device and Figure 20.14(b) that for AN automotive vehicle electrical device.

The latter shows that the secondary is really a part of the first, the present within the secondary being (I2 I1). Since the present is a smaller amount during this section, the cross-sectional space of the winding are often reduced, that reduces the number of fabric necessary.

Figure 20.15 shows the circuit diagram symbol for an auto transformer.

Saving of copper in an auto transformer

For an equivalent output and voltage quantitative relation, the automobile electrical device needs less copper than a normal double-wound electrical device. this is often explained below.


 The volume, and thence weight, of copper needed in a very winding is proportional to the quantity of turns and to the cross-sectional space of the wire. successively this is often proportional to this to be carried, i.e., volume of copper is proportional to Ni.

                                   i.e., a saving of 80%

Advantages of auto transformers

The advantages of automotive vehicle transformers over double-wound transformers include:

1 a saving in value since less copper is required (see above) 

2 less volume, therefore less weight 

3 the next efficiency, ensuing from lower I^2R losses 

4 a unceasingly variable output voltage is accomplishable if a slippery  contact is employed 


5 a smaller share voltage regulation.

Disadvantages of auto transformers

The primary and secondary windings don't seem to be electrically separate, therefore if Associate in Nursing open-circuit happens within the secondary coil the complete primary voltage seems across the secondary.

Uses of automobile transformers


 automobile transformers area unit used for reducing the voltage once beginning induction motors  and for interconnecting systems that area unit operational at close to an equivalent voltage.