[RFI] Help on speed drive motor controller RFI
w8ji at contesting.com
Sun Jan 28 22:13:14 EST 2007
> Ask to see the documents for the declaration of "CE"
> conformance, which
> apply to every country in the European Union.
> On the face of it, it seems impossible that such a system
> could meet the
> regulations for conducted emissions of 15kHz and its
> harmonics without
> using RFI filtering.
Having had first hand experience with this exact problem,
put me on the record as disagreeing. A controller can easily
pass conducted emissions in CE or FCC testing by a wide
margin and be horrible near an amateur or commercial HF
I've cleaned up speed controllers (three phase from a German
company) and filter and suppression help from the
manufacturer is useless. They don't understand radiated
noise, and the filters they sell have excellent suppression
below the HF bands but don't do much at all at HF. The fact
it is FCC approved or CE approved doesn't mean a thing when
the controller is near radio gear, especially if it is used
in or near an HF system.
I've made systems I've worked on so noise-free you can hold
a receiver next to the case and not hear the controller, but
I had to design custom filters in RF tight boxes for the
motor leads, control, and power leads. The entire controller
had to be enclosed in a properly designed box with copper
screening over the vents and everything entering and leaving
through multi-section shielded filters. The filters also had
to withstand the high transient voltages and high starting
currents of the inductive load while not causing the peak
current to be out of spec for the controller. It was
designed to look into an inductive load and there were
cautions about using it into a capacitive load beyond a
The power line is not the issue, the line to the load is.
More information about the RFI