A 10A power supply is not always a 10A power supply in the real world.
Published on 11 June, 2026 in Industry 4.0
That number on the label is a rating, not a promise. It's the current the unit can deliver under a defined set of conditions, and the conditions inside a real control cabinet are rarely the ones on the datasheet's front page.
Most sizing exercises start the right way: add up the loads. Controller, I/O, sensors, an HMI, a handful of relays. Sum the steady-state draw, add a margin, pick the next size up. Sensible, but it only accounts for the load on a good day, sitting still.
Real machines don't sit still. Contactors and solenoids pull far more on pickup than they hold at. Capacitive loads: HMIs, industrial PCs, DC/DC converters, electronic protection modules, and anything with a bank of capacitors on its input can look momentarily like a short circuit at power-up. Add enough of them and your "well within budget" supply can be driven into current limit or hiccup mode at the worst possible moment: switch-on. The peak demand, not the average, is what decides whether the machine starts reliably.
