On the west side of the Pond, the major discrimination (for emissions) was in 
the application of the class A limit at 10 meters, vs. the class B limit at 
three meters. The differentiator was the expected zone of control. Meaning an 
apartment dweller might not have control over an offending interference source 
more than three meters away, vs. an industrial or commercial enterprise where 
the zone of control would typically be larger.

 

The same kind of reasoning would apply to conducted emissions, both from the 
point of view of a radiating power line, but also what culprits and victims 
might share the same or a close-by branch circuit.

 

-- 

 

Ken Javor

Ph: (256) 650-5261

 

 

From: "James Pawson (U3C)" <ja...@unit3compliance.co.uk>
Reply-To: "James Pawson (U3C)" <ja...@unit3compliance.co.uk>
Date: Saturday, November 9, 2024 at 10:19 AM
To: <EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: [PSES] Emissions Class A vs Class B

 

Hello all,

 

I’m writing some guidance on Class A vs Class B and I was thinking about the 
Why. As in why do we separate emissions into Class A and B?

 

Reasons I’ve heard (which make some kind of sense even if I’ve not actually 
looked into the figures) include:

 
Concentration of electronic equipment – domestic premises are more likely to 
have other interference equipment operating in closer proximity to receivers 
than in a commercial/industrial environment.
 
Quantity of devices sold – consumer devices used in a domestic sphere have a 
much higher sales volume 
 
Nature of installation – Class A equipment installed by more technically 
competent users, Class B installed by less knowledgeable users.
 

Does anyone have any additional justification, historical perspective, or can 
point me in the direction of a standard that describes this in more detail?

 

I’ve looked in IEC TR 61000-2-5 which, although it mostly focuses on immunity, 
mentions these above reasons. CISPR 16-4-4 seems to deal with statistical 
methods. IEC TR 61000-1-1 deals in general terms with the concept of a margin 
between Emissions and Immunity. But no definitions for the derivation of these 
Classes…

 

Thanks in advance!

 

All the best

James

 

James Pawson

Managing Director & EMC Problem Solver

 

Unit 3 Compliance Ltd

EMC : Environmental & Vibration : Electrical Safety : CE & UKCA : Consultancy

 

www.unit3compliance.co.uk | ja...@unit3compliance.co.uk 

+44(0)1274 911747  |  +44(0)7811 139957

2 Wellington Business Park, New Lane, Bradford, BD4 8AL

Registered in England and Wales # 10574298

 

Office hours:

Every morning my full attention is on consultancy, testing, and troubleshooting 
activities for our customers’ projects. I’m contactable between 1300h to 1730h 
from Monday to Friday.

For inquiries, bookings, and testing updates please send us an email on 
he...@unit3compliance.co.uk or call 01274 911747. Our lead times for testing 
and consultancy are typically 4-5 weeks.

 

 

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