Power distribution for solenoids of pneumatic valves
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For pneumatic valves, should the solenoid valve be powered by 220VAC or 24VDC? Should it be powered by the DCS using 24VDC, or should a separate power distribution box be used?
Generally, 24VDC is used to supply power directly from the components in the DCS cabinet to the coil of the solenoid valve; it is important to ensure proper power matching. To prevent coil short circuits, a 2A fuse can be installed in the coil circuit
Either one will work, but the 220V coil tends to burn out; maybe the quality of the one I bought was poor. It is recommended to use a 24V model with low power consumption.
Now, low-power 24V solenoid valves with a power consumption of less than 4W are preferred
A 24V one will work; it can provide direct output via the DO card on the DCS
Generally, low-power 24V DC relays with a power consumption of less than 3W and normally open operation are selected. Based on the power of the solenoid valve, calculate the appropriate length for its cable; avoid situations where the high power of the solenoid valve results in insufficient voltage supply, as this is mainly caused by cable voltage drops.
All the designs I create are low-power 24VDC systems with a power consumption of ≤3W; 3/24 = 125mA. The output modules are driven directly, and typically the DO channels can handle 500mA, so there’s no problem.
If 24V is available, definitely use it – it’s safer.
Either is acceptable, but nowadays solenoids used with valves are generally selected to operate at 24V; they are usually powered by a DCS system and do not require separate power supply. Of course, many complex control circuits also use 110V or 220V.
In cases where 24V DC field valves are located far away from the control room, the voltage of the 24V DC current decreases as it passes through the cable impedance before reaching the field devices. Therefore, our company recommends using 220V AC.
Considering the site conditions – it’s too far from the control room and the explosion protection is not sufficient – 220V is used, while 24V is used for everything else. Solenoids are generally powered separately; it is best not to draw power from the DCS cabinet