What ratio does an auto transformer usually have?

An autotransformer is a type of electrical transformer that shares common windings for both the primary and secondary sides. This design allows for a more efficient and compact transformer since it requires fewer materials compared to traditional transformers. The ratio of an autotransformer refers to the relationship between the number of turns of wire in the primary winding versus the secondary winding.

A common ratio for autotransformers is 2:1. This means that the secondary voltage can be twice the primary voltage, benefiting applications that require a specific increase in voltage. For instance, if the input voltage is 120 volts, the output voltage would be 240 volts, which makes the autotransformer suitable for applications like voltage boosting in power distribution.

By understanding that a 2:1 ratio allows for voltage transformation while maintaining efficiency, it becomes clear why it is a standard ratio for autotransformers in practical use.