Tnx fir the good info so far. Does anyone have experience with recent
Bryant units?
73, Dan
On Mon, Nov 11, 2024, 7:47 PM Steve Dyer W1SRD via RFI <rfi@contesting.com>
wrote:
> I think the take away is variable speed motors are not "evil". Properly
> engineered (like anything else) they bring a ton of benefits.
> My 11 year old Bryant Evolution Extreme heat pump is RFI silent. It has
> a variable speed compressor in the outdoor unit and PCM blower in the
> indoor unit. Really high quality stuff and silent in the audio range as
> well. One of the most energy efficient air-source heat pumps made.
> 73,
> Steve
> W1SRD
>
>
>
> On 11/11/2024 1:14 PM, Jim Brown wrote:
> > Almost 30 years, Neil Muncy, W3WJE, (the Pin One Guy), showed me and
> > an pro audio RFI colleague an in-house engineering report from a mfr
> > of large variable speed drives. They were having problems with RFI
> > from the drives screwing up the control circuitry from those drives,
> > and identified the wiring between controller drive as a principal
> > mechanism. The common thread was that the controllers and motors were
> > widely separated.
> >
> > We were interested because RFI from drives running elevator motors was
> > getting into microphone circuits in large sound systems. A system Neil
> > was working on was at large performing arts center in NJ.
> >
> > A few years later, at a church in Dayton where I was inspecting a
> > sound system I'd designed, I ran into an EE who specialized in EMC. We
> > got to talking, and the conversation turned to variable speed drives
> > in large installations. He volunteered that interconnecting wiring was
> > the culprit, and we agreed that all of the current-carrying conductors
> > had to be twisted pairs, which was the same solution Neil found.
> > Obviously, making the controller and motor a single integrated package
> > is also a great solution for smaller systems.
> >
> > 73, Jim K9YC
> >
> >
> > On 11/11/2024 12:12 PM, Gary Johnson via RFI wrote:
> >> 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.
> >
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>
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