24V Power Supply for PLC and Control Systems
24VDC is the control voltage in IEC 61131 systems for a reason: safe to touch, low drop over panel wiring, and standardized. Sizing it is load current plus headroom plus inrush.
Why 24VDC
IEC 61131 control systems run on 24VDC: below the shock-hazard threshold, low enough current for thin panel wire, high enough to beat noise and voltage drop across a cabinet.
Sizing: Sum and Add 30%
Add the current of every module, sensor and relay coil on the rail, then multiply by 1.3 for headroom and future expansion. A 4A load -> a 5A-plus supply.
Inrush
Some loads (contactors, solenoids) pull several times rated current at switch-on. Check the supply's peak-current rating, or stage the loads.
DIN Rail and Redundancy
Snap onto 35mm DIN rail (EN 60715). For critical lines, use two supplies with OR-ing diodes so one can fail without dropping the PLC.
Can I mix 24V and 12V devices on one rail?
Not directly. Step the 12V loads down with a DC-DC converter from the 24V bus.
Why 1.3x and not exactly the load?
Headroom covers inrush, aging and added modules; a supply at 100% runs hot and short-lived.
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