The fluid medium used in pneumatic solenoid valve is compressed air, which has low viscosity and fast action, and is used in automatic production lines. Solenoid valves are divided into DC solenoid valves and AC solenoid valves. DC solenoid valve generally uses DC24V power supply, which needs to be equipped with AC-DC switching power supply; AC solenoid valve directly uses AC220V mains power, which is more convenient, but not as safe as DC24V power supply.
One. AC solenoid valve
In order to reduce the heat loss of the iron loss of the AC solenoid valve, the core is generally made of steel sheets, and there is a short-circuit ring (magnetic division ring) on the end face of the pole part to eliminate the fluttering noise caused by the change of suction. AC solenoid valve is an inductive load, the inductor is an energy storage element, not an energy-consuming element, Figure 1 is a solenoid valve coil marking parameters.
As can be seen from the figure, the power unit marked is VA (volt-ampere), not W (watt), because the AC solenoid valve coil and the core form an inductance L, the inductor and the power supply only exchange energy, do not consume energy, the exchanged energy is called reactive power Q; The energy consumed by the solenoid valve coil resistance R is the active power P, and the commonly used apparent power S comprehensively reflects these two powers.
Although the inductor does not consume energy, the impedance (inductive reactance) of the inductor prevents the AC current from becoming larger and indirectly affects the amount of active power. In summary, it is more scientific for the solenoid valve to express power consumption with apparent power S, and the apparent power unit is VA. The relationship between active power, reactive power and apparent power of the solenoid valve also follows the power triangle, as shown in Figure 2, so let’s review it.
AS SHOWN IN FIGURE 1, WHEN THE FREQUENCY IS 60HZ, ITS INDUCTIVE REACTANCE IS GREATER THAN 50HZ, THE CURRENT IS LESS THAN THE CURRENT AT 50HZ, AND THE APPARENT POWER S=UI BECOMES SMALLER.
100% ED: ED stands for power-on rate, that is, the proportion of power-on time in a duty cycle. 100% ED means continuous energization;
IP65: indicates the degree of protection, the preceding number indicates the degree of protection against solids, and the following number indicates the degree of protection against liquids. Therefore, 6 represents solid protection level 6, which is the highest level, which means that it is sealed without a tip; 5 stands for liquid protection level 5, which means that it can prevent splashing water in any direction.
Temp.rise35: The temperature rise is 35 degrees Celsius.
Two. DC solenoid valve
Its core is a whole piece of mild steel, the excitation current is only related to the coil resistance, the resistance is an energy-dissipating element, and the power consumed is the active power P, therefore, the DC solenoid valve power unit is standard W, see Figure 3. DC24V DC frequency is zero, there is no inductive reactance, but it also hinders the sudden current (including various frequencies) at the moment of power-on, so the suction power is small when it is just powered on, and the suction force is stable after suction.
Voltage range: DC19.2V~26.3V, indicating the DC voltage range of this solenoid valve, outside the range may not work or burn the solenoid valve coil. Other parameters are synonymous with AC coils.
Three. Application considerations
In the process of AC solenoid valve, the current cross-cutting is very large. At the beginning, the inductance is small, the inductive reactance is small, and the current is large; As the air gap decreases, the magnetoresistance decreases, the inductance and inductive reactance of the coil increase, and the current gradually decreases. If the valve core is not well lubricated, or the grinding is rough, the moving iron core is blocked and not in place, the inductance and inductive reactance are small, the current will be large, the active power will be large, and the coil will be seriously heated and burned.
The switching power supply for DC solenoid valve must have sufficient power, with overload and short circuit protection functions, and can output stable DC24V voltage. The voltage becomes smaller, and the valve may not open; If the voltage becomes larger, the coil will be seriously heated and burned out;
4. Commonly used two-digit five-way solenoid valve character identification
P: Air intake (Pressure Source);
A, B: working port (even with actuators, providing working air path);
R, S: vent port (even silencer, also known as exhaust port, exhaust air);
Arrow: the direction of the air path of the internal interconnection port;
Square: represents the position status of the valve, and a few boxes indicate how many valves.
T: This port is not connected to other ports.