GFCIs have a simple and well defined function. What is the current through one lead? What is the current through the other lead? Do they differ by more than x amount? If so, trip.
AFCIs are a whole different thing - the plug is trying to predict when arcing is happening somewhere downstream of it and it has very little in the way of 'processing' power to do it, so generally there is a classical filter that is designed to detect the characteristic harmonics of the current waveform that are inherent to an arcing condition. When you experience a sharp upward or downward step in power draw you introduce harmonics, when you have capacitive coupling between SMPS you introduce harmonics, motors often introduce harmonics, etc.
There's like a zillion things that can create AFCI trip conditions and cause spurious trips and frustration for users, and there's very few documented cases of them doing the thing they're supposed to do. I think it's a case of someone being well intentioned but releasing regulatory guidance to use a product that isn't quite there in terms of technology maturity.
Agreed on AFCI circuit breakers! They are now mandatory for all 15-20 amp light and plug circuits on new construction where I live - although breakers for large appliances do not require them. But I have several portable tools (eg a carpet cleaner) which will make an AFCI breaker trip every time. AFCI circuit breakers seem to be more fragile (read the box: much smaller range of acceptable heat and limited number of duty cycles) - I apparently killed one just by tripping it repeatedly. And while a regular 15 amp breaker is a few bucks, the CAFCI breaker I'm supposed to use is $45...
AFCIs are a whole different thing - the plug is trying to predict when arcing is happening somewhere downstream of it and it has very little in the way of 'processing' power to do it, so generally there is a classical filter that is designed to detect the characteristic harmonics of the current waveform that are inherent to an arcing condition. When you experience a sharp upward or downward step in power draw you introduce harmonics, when you have capacitive coupling between SMPS you introduce harmonics, motors often introduce harmonics, etc.
There's like a zillion things that can create AFCI trip conditions and cause spurious trips and frustration for users, and there's very few documented cases of them doing the thing they're supposed to do. I think it's a case of someone being well intentioned but releasing regulatory guidance to use a product that isn't quite there in terms of technology maturity.