Microwave trips the AFCI almost every time it is used
Your electrician is way wrong a 1.5Kw device only draws 12.5 amp a 20a breaker won’t trip below 2400w for current (usually beyond that for current based on an inverse time ratio).
Microwaves convert the power to RF the wave shaping creates harmonics that the AFCI can not tell what they are.
The AFCI thinks they are arcs and trips.
This tripping gets more common with larger microwaves and heavily loaded lighting circuits with electronic ballasts/drivers, and motor controls like for washing machines.
Electronic circuits have this issue and in some cases changing brands of AFCI device if possible may help.
In my state I the option I have with a dedicated circuit I can omit these devices in cases like these where the device is known to cause nuisance tripping so it would be worth checking your local code amendments.