Calculation of inductance of homemade magnetic ring

乱世煮酒论天下

Calculation of inductance of homemade magnetic ring [Copy link]

I found a formula for calculating the inductance of an inductor coil in a book: , N is the number of coil turns, is the inductance of the magnetic ring, why is the inductance of the coil proportional to the cross-sectional area of the coil and inversely proportional to the length of the coil? Shouldn't the longer the coil, the greater the inductance?

The above formula is equivalent to abbreviated as , which is the inductance coefficient. I watched a video and made a 100 inductor . First, wind 7 turns of coil on the magnetic ring, use a bridge to measure the inductance at this time, use the previous formula to calculate the inductance coefficient, and then calculate the number of coil turns N required for winding the inductance, and then calculate the wire diameter, and calculate the wire diameter according to the current carrying capacity.

maychang

[Why is the inductance of a coil proportional to its cross-sectional area and inversely proportional to its length? Shouldn't the longer the coil, the greater its inductance? ]

Why is it proportional to the cross-sectional area of the coil? This is determined by the fact that the current generates a magnetic field and the change in the magnetic field generates an induced electromotive force. The process of proving this is quite lengthy and cannot be explained clearly in the post.

Why is it inversely proportional to the length of the coil? It can be considered this way: if the number of turns N remains unchanged, the longer the coil, the sparser the winding, which is equivalent to the current being distributed over a wider range, and the current per unit length of the coil becomes smaller.

maychang

By the way: This formula is not an accurate formula, but an approximate one. This is because the ideal conditions for calculating inductance are not available in reality. The statement that inductance is proportional to the square of the number of turns is also an approximation.

maychang

[Shouldn't it be that the longer the coil, the greater the inductance? ]

I don't know what your basis is for saying that the longer the coil, the greater the inductance.

From the fact that the SI unit of magnetic field strength H is ampere/meter, we can know that magnetic field strength H is measured by the current per meter of length. From this unit ampere/meter, we can know that if the current in the coil remains unchanged and the number of turns remains unchanged, the longer the length, the smaller the magnetic field strength.

乱世煮酒论天下

maychang posted on 2024-8-10 11:49 [Shouldn't the longer the coil, the greater the inductance? ] I don't know what basis you have for saying that the longer the coil, the greater the inductance. From the international standard of magnetic field strength H...

The conclusion that the longer the coil is, the greater the inductance is based on the fact that the longer the PCB trace leads are, the greater the parasitic inductance is. Back to this formula, the length l refers to the length of the wound inductor, not the length of the enameled wire used to wind the inductor. Now I understand

cemfbjs

Thanks for sharing, it is very detailed. I am learning relevant knowledge and will download it to study hard.