What device is responsible for causing harmonic voltages?

Transformers are devices that can create harmonic voltages in an electrical system. While transformers are designed to change the voltage level from one circuit to another, they can also introduce non-linearities, particularly when they are subjected to non-linear loads. This non-linearity can cause the generation of harmonic frequencies in addition to the fundamental frequency of the system. In essence, when transformers operate under conditions that deviate from their ideal scenarios—such as saturation or high load—it can lead to the distortion of the current waveform, resulting in harmonic distortion.

In contrast, capacitors and inductors typically play roles in filtering or reactive power compensation, and resistors are primarily used for energy dissipation without contributing to harmonic generation. Therefore, the transformer is the device best associated with the generation of harmonic voltages due to its potential to distort waveforms under certain loading conditions.