The solenoid valve can be divided into the AC solenoid valve and DC solenoid valve according to its power supply, using AC solenoid and DC solenoid respectively. As we know, the solenoid is mainly composed of solenoid coil and solenoid tube assembly. With the power on and power off of the solenoid coil, the movement and stationary of the armature core, the electromagnetic parameters of the solenoid change differently. The AC solenoid follows the change rule that the magnetic flux is constant, the electric current is changed, while the DC solenoid follows that the electric current is constant, the magnetic flux is changed. Under normal conditions, the magnetic flux determines the suction of the solenoid. Therefore, the design of the AC solenoid and the DC solenoid will be different to some extent. Next, we will talk about the structural features of the solenoid and how to increase the attraction of the armature core.
The Structure Features of the Solenoid
Each type of solenoid has its own features, among which the most important is its attraction characteristic. Next, we will compare them in accordance with their different structure and attraction characteristic.
The armature of the solenoid is subjected to two suction forces. The superimposed synthetic suction makes the suction of the solenoid in the air gap still very large, which is suitable to the solenoid valve with a large stroke.
The characteristic of the flapper solenoid is that the armature rotates around the fulcrum and its rotation angle is generally less than 15 degrees. Because of its simplicity, it is one of the most widely used structures in many modern AC and DC electrical appliances and in the magnetic systems of contactors. The attraction characteristics of the flapper solenoid are close to hyperbola, but it usually varies with the types of magnetic coil power supply.
The III type solenoid is divided into two types, namely, direct acting type and rotating type. Compared with the flapper solenoid, this kind of solenoid has three armature columns and the coil is placed on the intermediate armature column. If the sum cross-sectional area of the two III type armature columns that located on the two sides is equal to the cross-sectional area of the middle armature column, and the cross-sectional area of flapper solenoid’s each armature column is equal to that of the III type solenoid’s middle armature column, in the suction position, the torque of the III type solenoid is much larger than that of the flapper type.
How to Increase the Suction of Solenoid
- When the size of the solenoid valve is allowed, we need to choose large cross-section armature core. The large cross-section armature core has more magnetic flux, which may produce greater electromagnetic suction.
- Within the allowable range of armature core stroke, we need to reduce the length of the air gap. Because the magnetoresistance in the air is large, reducing the length of the air gap in armature core can reduce the magnetoresistance, thus making the magnetism stronger.
- The magnitude of the magnetic flux is related to the multiplication of coil turns and the current passing through the coil. We usually call the multiplication ampere-turn. When the armature core is fixed, the larger the number of ampere turns of the coil, the stronger the suction of the solenoid. When the size of the solenoid valve is determined, the size of the solenoid coil is limited. In order to obtain the strongest electromagnetic attraction within the limited range, there must be an optimum value for the number of coil turns or the line diameter to get a maximum number of ampere-turns. Therefore, in order to reach the strongest electromagnetic attraction, we need to increase the coil turns and reduce the line diameter or do conversely. In any case, we need to regard taking maximum ampere-turns as a rule. Of course, we also need to consider the influence of the power supply voltage on the coil parameters.