[RFI] Nasty strong noise

[Jim Brown]

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