AC solenoid valve
Alternating current is an electrical current whose magnitude and direction change over time. The current flows from a positive peak through zero to a negative peak and repeats at 60 cycles per second. The magnetic field is at its maximum when it reaches the positive or negative peak. When reaching the zero position, the magnetic force of the coil disappears. At this time, the iron core will be pulled out due to the elastic force of the bullet, so that the one-in-one-open action will produce noise or rattling. To improve the situation, a small copper ring must be placed in the groove of the core. Because the positive resistance of the copper ring is very small, it can induce a large current to generate a precise field. In this way, when the AC current is strong, the current on the copper ring can supply a magnetic field by itself to keep the iron core closed, avoiding A noise occurs.
When the coil is energized, the iron core is still fully open, the magnetic circuit is not yet connected, and the AC impedance is low. At this time, the current is very large. This large current is called the starting current. When the iron core starts to pull in, the air gap decreases, the AC current impedance starts to rise, and the coil current also starts to decrease until the iron core is completely pulled in. At this time, the current maintains a constant value, which is called the rated current. Generally, Under low conditions, the starting current can reach 3-10 times of the rated current.
Since the heat dissipation capacity of the coil is designed according to the rated current, a continuously loaded coil can dissipate the heat generated by the rated current, but it cannot dissipate the heat generated by the starting current. So every time the coil is activated, the temperature rises a little bit. If the number of actions is too many, if the heat generated exceeds the cooling capacity of the coil, the coil will burn out.
DC solenoid valve:
The magnitude and direction of the DC current do not change with time, and the current is always constant, so it does not need to install copper rings. And there is no extremely high starting current. So it is not easy to burn. But when energized, the current creates some delay in the coil windings, making the valve move slower.
AC solenoids have a response time of 5-8 microseconds, while DC solenoids typically have a response time of 30-40 microseconds.
1. The DC 24v solenoid valve needs a DC power supply, but the 220v AC solenoid valve does not.
2. DC 24v solenoid valve, low voltage, high safety factor, 220v AC solenoid valve, high voltage may easily cause safety accidents.
3. If the DC 24V solenoid valve and the 220V AC solenoid valve have the same power, the current of the 24V DC coil is about 9 times that of the 220V AC coil. The driving current of the 220v AC solenoid valve is small.
4. There is a short-circuit ring in the coil core of the AC 220v solenoid valve to reduce vibration, and there is no short-circuit ring in the 24V DC solenoid valve.
5. Once the coil of the 220v AC solenoid valve is stuck, or the matching of the suction stroke is too large, resulting in poor suction, or the short-circuit ring falls off or is open, noise will occur, and the coil will quickly heat up and burn. So we often see the 220V solenoid valve coil burn out.
6. The AC 220v solenoid valve coil is noisy when it is energized, and the sound of the DC 24v is much smaller.
7. The suction of DC 24v solenoid valve is small at the beginning, and after the suction is much larger and the suction is relatively stable. The suction of 220V AC solenoid valve is alternating and there is sound.
Summary: In terms of safety, we give priority to 24v DC solenoid valves, and we choose AC solenoid valves when there is no DC power supply!