# The inductor blocks the alternating current completely

Inductance is a closed loop property, that is, when the current flowing through the closed loop changes, an electromotive force appears to resist the change in the current. This type of inductance is known as self inductance, which is the nature of the closed loop itself. Assuming that the current changes in one closed loop, an electromotive force is generated in another closed loop due to induction. This inductance is called the mutual inductance.

The inductance is expressed by the equation as u = Ldi / Dt;

Among these, u is the electromotive force, L is the inductance, i is the current, and t is the time.

The inductance is an obstacle to alternating current. At a constant alternating current frequency, the resistance is smaller, the greater the inductance, the greater the resistance to alternating current, the smaller the inductance. In addition, when the inductance is constant, the higher the frequency of the alternating current, the greater the resistance of the inductor to the alternating current, and the lower the frequency, the smaller the resistance of the inductor to the alternating current. In other words, the inductor has the property of preventing the passage of alternating current and passing direct current.

The ideal inductor is a pure inductance. It has no capacity to pass alternating current and no resistance to pass direct current, and there is no loss. No matter how large or small its inductance, it can completely prevent AC current from being passed on.

But there is no such inductance. Precisely for this reason an inductance was applied. We can use the inductor in the rectifier circuit because if we want to get a powerful DC power supply we need to use the rectifier circuit to convert the AC power to the DC power we need. And because the rectified DC power is not pure DC power, it contains a lot of AC components that we don't want so that we can connect the inductors in the rectifier circuit in series. After the rectified DC power flows through the inductors, the AC components it is greatly reduced. The DC component can be transferred to the responsibility due to the resistance of the inductor.

It can be seen that after the alternating current has passed through the inductor, the amplitude becomes smaller and the part with the smaller amplitude does not go anywhere but is blocked and nothing changes.

Because of the cost, the inductor cannot be made very large, so the inductor's ability to block AC current is also limited. The inductor's DC output still has some AC components. For this part of the AC components if this is not the case, we can connect a larger capacitor in parallel behind the inductance output circuit. By using the properties of the capacitor to block direct current and pass alternating current through, the unwanted alternating current components can be filtered out.

### The difference between common mode inductance and differential mode inductance

Common mode inductor and differential mode inductor circuit diagram

1. The annoyance electromagnetic field generates a differential mode current between the line and the line, causing a disturbance to the load which is a differential mode disturbance. The annoyance electromagnetic field creates a common mode current between the line and ground and the common mode. The mode current creates a differential mode voltage across the load that causes interference. This is common mode ground loop interference.

2. The filter inductor that suppresses common mode noise is called the common mode inductor, and the filter inductor that suppresses differential mode noise is called the differential mode inductor.

3. The common mode inductance is bidirectional, the differential mode inductance is unidirectional.

4. The common mode inductance consists of two sets of coils with the same number of turns on the same iron core, the same wire diameter and the opposite winding direction. The differential mode inductance is a coil wound on an iron core.

5. Common mode means that the two windings are connected to the neutral conductor or the live wire and the two windings enter and exit at the same time and the common mode signal is filtered out; the differential mode is a filter inductance with a winding connected separately to the neutral conductor and the live cable. Only differential mode disturbances can be filtered out.

6. Common mode signal: Two identical signals on the neutral or live wire are all coupled and grounded to form a loop. Differential mode signal: the same loop as the useful signal

7. The characteristic of common mode inductors is that the iron core is not afraid of saturation because the winding directions of the two sets of coils on the same iron core are opposite. The most widely used magnetic core material on the market is a ferrite material with high conductivity.

The characteristic of differential mode inductors is that they are used in large current applications. Since a coil is wound on an iron core and the current flowing into the coil increases, the iron core in the coil becomes saturated, so the most widely used iron core material on the market is powder metal core material. Especially the iron powder core material (due to its low price).