The process of calculating inrush current involves three steps, critical for protecting electrical equipment from the high surge of current when switched on. Inrush current, typically 2 to 3 times the steady state current of a device, can spike up to 30 times in devices like electric motors or transformers. Despite modern circuit systems’ efficiency and lower impedance, inrush current remains a concern, often leading to equipment overheating. Inrush Current Limiters (ICLs) are essential for controlling this surge and maintaining equipment safety.

To select an appropriate ICL, one must understand various parameters, including maximum output power, input voltage, reset time, single or three-phase system, filter or link capacitor value, scope trace of inrush current, and ratings of fuse, circuit breaker, and diode bridge if applicable.

Based on the above example calculations, we would have recommended either the Ametherm SL03 22102 or the Ametherm SL05 4R003. This ICL has a resistance of up to 220Ω (at 25°C), a maximum steady state current of 2A (up to +65°C) and a maximum total energy of 2J. If you would like to discuss any of your Inrush Current Limiter requirements, please contact one of our engineers today.