There is no "ground" in a vehicle, only "chassis". (Unless the vehicle
is on charge and connected to the grid.) The drivetrain and the AM radio
share the chassis "ground", which is likely the root of the problem.
The EMI comes from the controller PWM switching, goes into the chassis,
(and is radiated in general by the drive components,) and is received by
the AM radio.
The AM radio can be filtered, but that adds cost, is difficult, reduces
the sensitivity, and likely the sound fidelity of the AM radio. The
drive train can be designed to reduce the EMI in the specific frequency
region of AM, which adds significant cost, and is _/very/_ difficult.
You can locate the sensitive components of the AM radio away from the
drive train, which is a bit difficult and adds cost.
Is the cost worth the improvement of the AM radio reception? Most
folks don't care, and the added cost of clear sensitive AM reception is
not worth anything to them. Teslas answer is to "use streaming" instead
of the AM radio is probably the most sensible for most people.
This problem is similar to acoustic noise in airplanes. It is quite
costly to reduce the cabin noise in airplanes, and it adds weight, which
reduces efficiency and reduces performance. In small airplanes,
helicopters, and military airplanes, everyone wears headphones (or ear
plugs). In commercial airplanes, the airplane itself is designed to
reduce the cabin noise. However, it is very expensive to solve noise the
problem at the source end. Much cheaper and lighter to solve the problem
at the relieving end.
Do you _need_ an AM radio in your car? Probably not. You don't get
to your destination any quicker.
Bill D.
On 11/10/2018 1:03 PM, Peri Hartman via EV wrote:
Hmm, maybe cost savings of putting a grounded shield around the motor
and controller. For the AM radio, what could the cost be? $1.00?
Peri
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