Inrush current is a temporary increase in current when equipment is energized. In a switched-mode lighting power supply, charging internal capacitors can produce a short surge before the input settles to its operating level.
Why the operating rating is insufficient
A steady current rating does not describe the startup peak. Inrush depends on the power supply, supply voltage, switching conditions and any limiting circuitry. Its duration matters as well as its magnitude.
Practical example
Several fixtures switched on together can create a different startup demand from the same fixtures already operating. An installation may run normally after startup yet experience nuisance trips during simultaneous energization. Check documented fixture and switching-device limits rather than estimating inrush from the wattage printed in the model name.
Reading and measuring the surge
A useful specification identifies peak or RMS measurement, time interval and test conditions. An ordinary slow current display can miss a brief event. Follow the equipment manufacturer’s startup guidance and have the responsible electrical crew assess repeated trips; increasing protective-device ratings without checking the complete installation is not a remedy.
Related terms
Amperage · Power Factor · AC Power · Watt