Auto Transformer

An AutoTransformer is a single-winding electrical transformer. The prefix "auto" refers to a single coil functioning alone not to any form of automated device. In an auto transformer parts of the same winding serve as the transformer's main and secondary winding sides. A regular transformer on the other hand contains separate primary and secondary windings with no metallic conducting channel between them.

There are at least three taps on the auto transformer winding where electrical connections are made. Because a portion of the winding does "double duty" auto transformers are frequently smaller lighter and less expensive than traditional dual-winding transformers. Auto transformers also have lower leakage reactance smaller losses lower excitation current and higher VA rating for a given size and mass.

Construction of Auto Transformer:

It basically consists of two parts:

Conductors: The autotransformer's conductors are composed of copper. They have a poor level of resistance. The copper conductors are completely disconnected from one another. Impregnated paper mica and other materials are used as insulating material. Eddy current losses are also reduced by the insulation. The winding wraps itself around the center. When compared to two winding transformers a single winding transformer requires less copper.

Core: The core is utilised to transport flux from the primary to the secondary. The core is constructed of magnetic materials such as silicon steel CRGO steel and others. Because it has the lowest hysteresis losses CRGO steel is the most efficient material for core. The primary function of the core is to transport flux from one section of the winding to another.

Properties of Auto Transformer:

• An auto transformer is a device that is both electrically and magnetically connected.
• Power is constant in an autotransformer.
• The total flux in an autotransformer is constant.
• The frequency of an autotransformer is constant.
• Voltage and current are affected by the number of revolutions.
• A phase-shifting device is another name for an autotransformer.
• Because autotransformers use a single winding they have lower losses than two winding transformers.
• When compared to two winding transformers the autotransformer has higher efficiency.
• Both iron and copper losses are reduced by using an autotransformer.