What is a limitation of an auto transformer?

An auto transformer has various limitations, one of which is its inability to change the alternating current (AC) frequency. Transformers, including auto transformers, operate based on the principle of electromagnetic induction and rely on the frequency of the alternating current to generate voltage transformations. While they can increase or decrease voltage levels effectively, they do not have the capability to alter the frequency of the AC signal passing through them. The frequency is determined by the power supply, and the design of the transformer itself does not allow for frequency modulation. This is essential to understand, as frequency change is achieved through different methods such as frequency converters, not by any transformer type.

The incorrect options hinge on other operational characteristics of auto transformers. They are capable of handling high voltage levels and can regulate current effectively when designed properly, though they have limitations compared to traditional transformers in certain applications. The notion that they cannot operate at low frequencies is misleading; while efficiency may vary, auto transformers can function with low-frequency signals just as they can with standard AC frequencies.