> It is entirely possible to minimize and mitigate these conducted and radiated emissions.
Reducing EMI down at medium wave from motor drives is really, really hard. Filter networks that keep most of the switching frequency out of the motor and motor wiring are big, cost money, and reduce efficiency.
so instead of making the silent electric cars make some sort of noise for pedestrians to hear, they should all just carry a device susceptible to the EMI an EV generates to allow for proximity awareness of a silent EV approaching. /s
I know nothing about the technicalities of why this specific EMI is hard to eliminate, so I'm asking an honest question. Why? What makes it difficult to block this EMI? Where is it being generated (I'm assuming the motor windings??)? Is there not some sort of cage that can be built around the motors by lining the wheel wells to block the EMI?
Simple: motor inverters are switching power in this frequency range.
It’s already below FCC limits for unintended radiation - it’s not going to block AM activity far from the vehicle, but putting the antenna in the midst of all that radiated noise is challenging.
The motor controller is turning the motor on and off rapidly in this frequency range to control the power in each winding. The inductance of the motor converts this to a near-constant amount of power.
> cage that can be built around the motors
The motors already have shielding and the wiring does, too. But when every car has peak RF output of hundreds of kilowatts, not too much of a fraction has to leak out to completely jam the AM band.
Reducing EMI down at medium wave from motor drives is really, really hard. Filter networks that keep most of the switching frequency out of the motor and motor wiring are big, cost money, and reduce efficiency.