Dimming ballasts 1-10V / interference

[simonjay]

I have 4 x 36W T8 tubes on top of my kitchen cabinets so be connected to 2 dual dimming ballasts.

I tried Philips dimming ballasts, not mounted inside a luminaire, just fixed to the top of the cabinets. Short wires to one end of the ballast as required.
The RF interference generated from the ballast and/or wires was terrible and completely wiped out radio 4 on a radio 1.5 metres away.
I managed to get a refund on the ballasts.

Next to try Osram ? Someone I know has some approx 10 year old dimming ballasts from Osram installed in the same way as I described, and they cause no interference at all, even right up to the ballast. But have the Osram designs changed in the last 10 years ? A refund might not be so easy to obtain next time !

Do these HF dimming ballasts and wiring need to be inside an earthed box to achieve acceptable RF emissions ?

If so I might forget the dimming and get magnetic ballasts instead.

Simon.

 

[ericmark]

Have you earthed the brade on the cable between lights and HF unit?

 

[simonjay]

Have you earthed the brade on the cable between lights and HF unit?

There was no screening on the cable. The run was only to the other end of the tube and wired like you would inside a luminaire. It was twin-and-earth with the earth conductor unused.
However, using the FM radio as a detector, most of the interference seemed to be coming from the ballast itself - which was earthed.

A strange thing - if I connected a short wire to the ballast case and held it out then the influence of the my body was enough to almost completely stop the interference. The ballast was already earthed - checked right back to the incomer lead sheath.

Simon.

 

[andrewg6]

The liminaire was probably been tested for radio emissions "EMC" as a complete unit. Taking the ballasts (and more significantly the wiring) out of the surrounding metalwork allows the radio interference to escape. Even though the front of the luminaire is open, the metal fins across the front are enough to stop some of the radio escaping. Shielding the cables is another way to reduce the emissions. Wire of more than a few mm long will not earth VHF signals, hence the mains earth has no effect. The human body can also effect the signals in many ways, as it is conductive.