How does skin effect impact the drive system?
This short article provides a brief description of the skin effect and its impact on a drive system. As it will be explained, the skin effect influences the system in both negative and positive way. It always depends on the point of view.
What is the skin effect?
In simple words, skin effect is a physical phenomenon causing uneven current distribution inside the conductor. The highest current density is on the outer side while it reduces when going towards inside.
Consequences of skin effect
The fact that not the entire cross section of the conductor is optimally used leads to a poorer utilization of the material. The user pays for the conductor material (e.g. copper or aluminum) which is not used. Moreover, since the effectively used cross section is smaller than the physical cross section, the resistivity increases and the losses get higher. Increased losses affect the user twofold: higher power consumption raises the operating cost and additional losses require better cooling.
How does skin effect impact the drive system?
Now let’s look specifically at a variable speed drive system.
Skin effect can be a friend
The associations with skin effect are pre-dominantly negative: increased losses and higher energy consumption, more intensive cooling, risk of hot spots, worse utilization of the equipment, complex measures to reduce the skin effect…
However, skin effect can help as well. Presence of higher losses means higher dissipation, i.e. higher damping in the system. This is important in case of a resonance. Thanks to skin effect, the amplification at the resonance frequency is reduced. That is the case e.g. for a grid resonance. The skin effect significantly reduces the resonance peak and consequently the harmonic distortion. In this case it is a welcomed friend. The higher the resonance frequency, the better damping due to skin effect.
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References
[1] Network harmonics (series), MB Drive Services, https://mb-drive-services.com/category/net-harmonics/
[2] Skin effect, Wikipedia – The free encyclopedia, https://en.wikipedia.org/wiki/Skin_effect
