[RFI] HVAC

[Gary Johnson]

I wanted to mention one other good strategy that these new adjustable-speed drives are using: For most of the motors, they integrate all the power electronics right into the motor assembly, thus eliminating wires on the output side where the commutating waveforms and high circulating currents are present. Then they are applying proper RFI suppression to the incoming AC lines, again built right into the motor assembly. So the potential antenna lengths are greatly reduced and I’m seeing how effective this strategy actually is. The only motor without this approach is the big compressor, and that has a HUGE filter network nearby and also twisted wires to the motor, all inside a steel enclosure. Carrier was not being cheap or sloppy, and it shows.

Gary NA6O