On Wed,11/16/2016 1:09 PM, Sandro D'Onofrio wrote:
I will get in touch with the firm responsible for the maintenance and
assistance of our elevator,
Sandro,
This is an applications engineering problem, very likely the result of
how the variable speed drive controller for the elevator motor is
installed. Variable speed drive motor controllers are a well known and
powerful source of RF noise. They work by controlling the frequency
and/or pulse width of rectangular waves that drive the motor. That
current is carried by wiring between the controller and the motor, and
the controller is often located 10-15m away from the motor for convenience.
That wiring transmits the noise two ways, 1) as a magnetic field; and 2)
as EM radiation. The key to both is to 1) minimize the loop area of the
current path by using twisted pair(s) for each phase driving the motor
and by shortening the distance between the controller and the motor; 2)
enclosing the wiring in steel conduit, which provides shielding for both
the magnetic field and the electromagnetic field; 3) adding a line
filter to the mains side of the controller.
73, Jim K9YC
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