Harmonics in transformers can have a significant impact on the audible noise they produce. Audible noise in transformers is primarily generated by magnetostriction and the magnetostrictive effect, which occurs due to the mechanical vibrations caused by the magnetic core's cyclic changes in magnetization. Harmonics can exacerbate these effects in the following ways:
Increased Core Vibrations: Harmonics in the transformer's input voltage or current result in a non-sinusoidal magnetic flux waveform, which leads to uneven magnetization and demagnetization of the core. This uneven cycling of the core's magnetic domains can increase magnetostriction, causing more mechanical vibrations in the transformer.
Resonance Phenomena: Harmonics can lead to resonance phenomena within the transformer, where certain components or sections of the transformer resonate at specific frequencies. These resonant frequencies can amplify the mechanical vibrations, causing higher levels of audible noise.
Higher Frequency Components: Harmonics introduce higher frequency components into the transformer's magnetic flux and eddy currents. Since the magnetostrictive effect and associated mechanical vibrations depend on the frequency of the magnetic changes, higher frequency harmonics can lead to more pronounced noise generation.
Additional Losses: Harmonics can lead to increased core losses and additional heating in the transformer. This extra heat can exacerbate the magnetostrictive effect, resulting in a higher level of audible noise.
Manufacturers of transformers take these factors into account during the design process to minimize audible noise. Techniques to reduce audible noise in transformers include:
Using High-Grade Laminations: High-quality, low-noise laminations with specific grain orientation can help reduce magnetostriction effects.
Optimizing Core Design: By optimizing the shape and size of the core, manufacturers can minimize the risk of resonance phenomena.
Damping Mechanisms: Adding damping materials or structures to the transformer can absorb and dissipate mechanical vibrations, reducing audible noise.
Winding Design: Careful design of winding arrangements and conductor choices can also influence the noise level of the transformer.
Filtering Harmonics: In some cases, using filters to reduce harmonics in the input voltage or current can mitigate their impact on audible noise.
It's important to note that while these measures can significantly reduce audible noise, it is challenging to completely eliminate noise generation in transformers. Therefore, careful consideration of transformer placement and noise insulation is also essential in applications where low noise levels are critical.