Friends in electrical engineering, many times we listen about Skin Effect and Proximity Effect. But many people are always confused between proximity effect and skin effect.
But after reading this post, you will practically understand skin and proximity effects. Also, If any question related to these is asked in an interview, then you can answer it with full confidence.
What is Skin Effect?
In the DC system, the current magnitude doesn’t change with time, as we can see below.
It means constant current flow in the DC system. In DC system, the current will flow uniformly through the cross-sectional area of the conductor.
But if we talk about the AC system, then the magnitude of the AC system changes with time. So flux produces due to the AC also changes with time.
Friends, as current flows through the minimum resistance path, the same flux always goes through the lowest reluctance path. If we talk about reluctance, then reluctance is like resistance that opposes the flow of the flux.
Note: Flux always flows from the inside(center) of the conductor wire because air is present outside of the wire, and we all know that the reluctance of the air is very high.
When flux flows through the wire, the resistance inside the wire increases, but the flux does not flow from the outside surface of the wire, so the surface resistance is less than the inside resistance.
Due to the high resistance inside of the wire, current does not flow inside of the wire, only on the outer surface where the resistance is less.
Friends, instead of a uniform flow of current in the entire wire, current flow from the surface is called Skin Effect.
As you can see in the above photo that only on the outside surface where is red color, current flows through it. Inside where is a white area, there is no current flowing.
Friends, we have talked about what is skin effect. Now let’s talk about what are the disadvantages of the skin effect.
Disadvantages of Skin effect
High Reluctance:
As we discussed above, its reluctance increases when flux flows from inside the wire; due to this, our current flows through the surface only.
So friends, the area inside the wire where the current does not flow, that part of the wire is useless for us. So useful area gets reduced.
Loss:
Copper loss (I²R) will occur when current flows inside a wire. These losses are completely changed in heat. Due to the skin effect, the resistance increases, so the copper loss also increases, and our conductor heats up.
Why Skin effect occurs?
High frequency:
When the frequency increases, the reluctance (XL = 2×π×f×L) increases, and the skin effect also increases.
Area of conductor:
When the cross-sectional area of the conductor increases, the skin effect also increases.
How to Reduce Skin Effects?
We use strand conductors to reduce the skin effect. If we understand the stranded conductor in simple language, we make a big thick conductor wire by joining very thin wire.
As we mentioned above, if the conductor cross-sectional area increases, the skin effect also increases, but in a stranded conductor, we use a thin conductor. They have a smaller area, so they have less skin effect. We also get more total surface area from smaller wires.
What is the Proximity Effect?
Like the skin effect, the proximity effect is also caused by the A.c current. Friends, a magnetic flux is generated around the wire when current flows through a conductor.
In an overhead transmission line, conductors are very far from each other, but in an underground cable, the conductors are placed near each other.
When the magnetic fluxes of both the conductors cut each other, the reluctance inside the conductor increases; due to this, less current will flow inside the conductor. This effect is called the proximity effect.
Friends, the proximity effect mainly occurs inside the underground cable because their conductors are placed very close to each other. In the overhead line, there is a lot of distance between the conductors, so they are not affected by the magnetic field.
How can we reduce the Proximity effect?
- By reducing the size of the conductor, we can reduce the proximity effect.
- The proximity effect can be reduced by reducing the frequency.
- The proximity effect can also be reduced by increasing the distance between two conductors.
Interview Important Question
What is the Difference Between Skin Effect and proximity Effect?
Ans: The skin effect occurs in only one conductor, whereas the proximity effect occurs in two conductors.
How do you reduce Skin Effects?
Ans: To reduce the skin effect, we can reduce the frequency and size of the conductor. Apart from this, we can also reduce the skin effect by using stranded conductors.
Where does the Proximity Effect Occur?
Ans: The proximity effect mainly occurs inside an underground cable because there is less distance between the conductors.
We hope that you understand what the skin effect and proximity effects are. If any question is left, you can comment below or send the inquiry to us on Instagram “Electrical Dost.”
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