CHAPTER 2: Electromagnetic Conceptions

Single Solenoid Coil

A solenoid is essentially a coil of wire, typically made of copper. When an electrical current flows through the wire, it generates a magnetic field, similar to how a magnet works (see Figure 10).

                                             Figure 10

The solenoid often has a cylindrical shape, which helps to create  strong and uniform magnetic field.

Despite this, there may be variations in design. Solenoids have the potential to feature a D-shaped frame customized for specific applications. However, the prevailing perception of a solenoid usually corresponds to that of an elongated, cylindrical coil. [16]

Simple Simulation

                                            Figure 11

We used COMSOL Multiphysics to simulate a simple design consisting of a single solenoid with a cylindrical shape (4 cm in diameter and 5 cm in height).

We used 200 turns, a relative permeability of 200, and 6 amperes, and that was the result (see Figure 11).

The white arrows represent the flow of the magnetic field to determine its direction and uniformity.

We can observe that the maximum magnetic flux density is depicted in red in the center, gradually decreasing in intensity towards blue.

The simulation was conducted again with two solenoids positioned 15 8 cm apart to analyze the magnetic field between them (see Figure 12).

                                           Figure 12                         

As we can see, the magnetic field is uniform only in the middle, which is insufficient for our application. By employing additional solenoids, we can attain an even more uniform magnetic field.

The simulation indicates that the magnetic field density is insufficient to achieve a 60 mT (0.06 Tesla) strength between the two solenoids.

                                                Figure 13

When we increase the relative permeability to 3000, we observe that the maximum magnetic flux density also increases (4.42 Tesla to 65.9 Tesla) (see Figure 13).

But how can we determine the effect of permeability outside the coils where the relative permeability is one? This will be known after the following simulation.

                                          Figure 14

                                          Figure 15

We adjusted the scale to a maximum magnetic flux density of one milliTesla (1mT) to display the color distribution outside the coils (see Figure 14). When we reduced the relative permeability to 200, the arrow volumes representing the magnetic fields nearly vanished, suggesting a loss of uniformity (see Figure 15). However, we can see the arrow volumes again by readjusting the arrow scale.

Biot-Savart Law

Multi-solenoid Unit

Multi-solenoid is an electromagnet component that produces a consistent uniform magnetic flux density along a relatively large

C-shape Unit

References