Funny all this talk of variable frequency drives, etc, and this comes in
today mail......I got a letter from our local electric co-op,
introducing their new engineering manager, and enclosed was a copy of
their power quality policy. I've attached the relevant pages about VF
drives/motors.
------ Original Message ------
From "Kenneth Wyatt via RFI" <rfi@contesting.com>
To rfi@contesting.com
Date 2/14/2023 3:20:26 PM
Subject Re: [RFI] RFI Digest, Vol 241, Issue 21
Steve is correct that it’s possible to purchase large appliances that are designed with EMC
in mind (mostly for the European market). As an EMC consultant for the past 15 years, I’ve
helped several appliance clients with their washing machines, air conditioning systems, etc. achieve
EMI compliance. The problems I’ve seen include EMI mains filters located too far inside the
works, which allows noise coupling directly into the mains wiring. Also the VS drive electronics is
not fully enclosed with shielding. But the biggest problem is that the internal cable routing is
haphazard, allowing multiple coupling between noisy circuits and mains wiring, which can lead to
both radiated and conducted emissions.
I, and a handful of others, in the world also teach product design for
compliance to EMC and product safety, but these topics are largely ignored in
college and university. The result is that designers end up learning the hard
way about EMC and the end users bear the consequences.
Kenneth Wyatt
Woodland Park, CO
Sent from my iPhone.
On Feb 14, 2023, at 12:38, rfi-request@contesting.com wrote:
From: Steve Dyer W1SRD <w1srd@yahoo.com>
To: rfi@contesting.com
Subject: Re: [RFI] Fwd: RFI Digest, Vol 241, Issue 20
Message-ID: <ae833fd3-d6fb-7f0e-e8f2-8c7daf065431@yahoo.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Steve,
I guess you don't believe and want some evidence.
I have the Bryant Evolution Extreme (equivalent system to the Carrier
Infinity Greenspeed) and it is RF quiet. It was one of the conditions of
purchase I made with the installer. Both the air handler and compressor
are VS.
This is a 2013 vintage system so I have a few thousand hours in front of
the radio with the system on and off.
I live in a rural location so it's not masked by local noise. The beams
are within 100'.
I can stand right next to the outdoor unit with a SW radio and barely
hear anything.
I am extremely pleased with the systems lack of RFI, efficiency and home
comfort.
Variable speed systems can be engineered well for EMC.
73,
Steve
W1SRD
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