Introduction to types of PLC power supplies
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What types of PLC power supplies are there?
Five types cover the field: AC-input supplies converting mains to logic-level DC, DC-input supplies for systems already fed with direct current, UPS-backed arrangements for critical processes, switch-mode supplies (the modern standard, chosen for efficiency and compact size), and redundant pairs that ride through a supply failure automatically. Selection follows the cabinet: what input power exists, what the process costs when power blinks, and whether the application justifies duplication.
The five types
| Type | Input / output | Typical use |
|---|---|---|
| AC-input supply | Mains AC in, logic-level DC out | Standard cabinets fed from mains |
| DC-input supply | DC in, regulated DC out | Systems already fed from a DC distribution |
| Switch-mode (SMPS) | High-efficiency conversion | The standard in current installations: efficient, compact, less heat |
| UPS-backed | Battery ride-through | Critical processes where a power blink causes damage or loss |
| Redundant pair | Dual supplies, automatic failover | Control rooms, safety-adjacent and high-availability systems |
Scroll the table horizontally to view all columns.
Source: general PLC power-supply practice per manufacturer documentation. Efficiency and capacity figures are per the specific product's datasheet.
Selection logic
- Start from the input power the cabinet actually has (AC or DC, which voltage), which narrows the type immediately.
- Size from the load: total the controller, I/O and expansion draw, then choose the next size up so the supply runs below its ceiling; a supply run at its limit produces faults that look like controller problems.
- Add protection and conditioning where the process justifies it: UPS ride-through for critical processes, redundant pairs where a supply failure alone cannot be tolerated.
- Keep the brand consistent with the rack where the family specifies matched supplies, so ratings and diagnostics line up.
The other peripherals around a controller (I/O modules, communication modules, special-function modules) follow the same pattern: size from the real list, add growth margin, and prefer matched-family parts where the manufacturer documents them as such.
Sourcing help
KOEED supplies PLC power supplies and peripherals across the major brands, in active and EOL stock. Send the rack configuration for a sized quote.
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