class x + class x = class x

[Mona Akerblom]

Hi there EMC/PSTC folk:

There's been a number of discussions here about the validity of  "Class
X + Class X = Class X" in the various FCC and CISPR EMC requirements.

Bypassing the whole "is it appropriate" question, where exactly is it
written that this is acceptable?  Is it written in the standards
themselves?

I'm mostly involved in working with our system HW design to make sure it
passes, and haven't gotten much involved at all in the reading and
interpretation of the actual standards, or interfacing with the
agencies, i leave that to our Regulatory Affairs group.  As such, I
haven't personally read the standards myself (yet!), so pardon the
basic-ness of my question ;-).  Unfortunately, I'm starting to need to
know this sort of thing, and need to start arming myself with standards
and supporting documents.

if someone could point me to the appropriate document (if not written in
the actual standard), or section of the standards so i can look this up,
i'd be greatly appreciative.  I'm mostly only interested in CISPR 11A
(EN5011A), but wouldn't mind pointers for FCC Class A as well.

Thanks so much in advance,
Mona Akerblom
Acuson Corp.


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spec'ing OEMs, Was: Re: Power Factor

[Mona Akerblom]

Another nice thing to specify to vendors is the MARGIN you expect the full
system to have versus the limits when the OEM part is installed into your
equipment.

we try to have a 6dB margin for EMC, but that's often not attainable, so a
3-4dB margin is what we'll "live with".  unfortunately, when you spec "must
passs XXX when installed into the system", all you are asking for is 0.1dB
margin, just enough to not fail.  so much for any headroom to allow for unit
to unit and test site to test site variations!!

mona

Gary McInturff wrote:

> I might add that I specify that the power supply will meet all of the
> requirements when installed into our equipment. That eliminate the
> fights between the test configuration and results. The power supply
> manufacturers are often using resistive loads to run their tests. That
> can give dramatically different results because switchers have (or used
> to at any rate) quite different characteristics when fully loaded and
> lightly loaded. The equipment I run falls somewhere in between. This get
> to be a really interesting issue when specifying the EMC compliance.
> Make sure to specify that the supply works in your system and the
> voltage range you expect out of it. Most folks run the conducted
> emissions test to the CISPR limits for radiated. The FCC allows that but
> states that if  you accept those limits for radiated then  you must
> accept them for the conducted. That means your supply has to meet the
> CISPR levels down to 150 kHz and 120 Vac - Not 450 KHz at 120 Vac. This
> can be a very important point for your power supply vendors. They have
> to start being careful as the frequency range of measurement goes down
> at the same time the input frequency goes down and the load on the power
> supply is not maximized. In fact I specify the voltage to be 100 Vac to
> meet Japans line voltage. I think VCCI accepts the voltage at 120 Vac,
> but I demand 100 Vac.
>
>
> -Original Message-
> From:   Rich Nute [SMTP:ri...@sdd.hp.com]
> Sent:   Thursday, August 06, 1998 5:57 PM
> To: s_doug...@ecrm.com
> Cc: emc-p...@majordomo.ieee.org
> Subject:Re: Power Factor
>
> Hi Scott:
>
> In answer to your questions:
>
> >   1.  What is the standard that addresses power factor
> correction?
>
> IEC/EN 61000-3-2.
>
> >   2.  What is the range of acceptable power factors for ITE?
>
> The standard does not specify power factor.  Instead, it
> specifies the maximum harmonic current emitted by the
> product.  Limits are specified for each harmonic up to the
> 39th harmonic in both absolute and relative units, depending
> on the type of product.
>
> Some engineers may be able to correlate the harmonic limits
> to power factor.  But, power factor is NOT the measure of
> compliance.
>
> >   3.  How should I call out PFC in my power supply spec?
>
> Simple!  We specify compliance to IEC 61000-3-2.
>
> As a general rule, rectifier circuits such as commonly used
> in electronic equipment power supplies, whether linear or
> switcher, will not comply with the harmonic current emission
> requirements.
>
> As a general rule, products with PFC circuits on the front
> end of SMPS will comply with the harmonic current emission
> requirements with lots of margin.
>
> EN 61000-3-2 is applicable to products in the EU.  It has
> not been adopted elsewhere in the world.
>
> Best regards,
> Rich
>
> -
>  Richard Nute Quality Department
>  Hewlett-Packard Company   Product Regulations Group
>  San Diego Division (SDD)  Tel   :  619 655 3329
>  16399 West Bernardo Drive FAX   :  619 655 4979
>  San Diego, California 92127   e-mail:  ri...@sdd.hp.com
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Re: UL Approved vs Recognized

[Mona Akerblom]

hi Doug:

in my experience, UL Approval is available only for complete systems, UL
recognition is available for components.  E.g., an internal disk drive could
only be UL Recognized, but a stand-alone external disk drive with its own power
supply could be UL Approved.  Wire, being a component, could never be UL
Approved on its own, but if you build a system with UL Recognized wiring, life
is easier for you when you attempt to get UL Approval for your overall system.

Mona Akerblom
akerb...@acuson.com

POWELL, DOUG wrote:

> Hello group,
>
> I have recently been in discussions about what is the "real" difference
> between UL Recognized and UL Approved.  In this instance it was about wire
> but I believe that it applies to most any product.  If UL recognition is not
> as rigorous as approval but am I able to rely on recognized parts for safety
> applications?  Just what is the distinction?  My experience has been with
> NRTL/C and GS marking but never component approvals through UL.
>
> Thanks,
>
> Doug Powell, Compliance Engineer
> Advanced Energy Industries, Inc.
> Ft. Collins Colorado USA

Frequency allocation charts for Europe?

[Mona Akerblom]

Hello emc-pstc list:

a number of months ago someone sent out a pointer to a web page with
the US Frequency allocation chart 
(http://www.ntia.doc.gov/osmhome/allochrt.html), which has been 
helpful to me recently.

does anyone know where one might find a similar chart for European
Frequency allocation?  snail mail, web page, or organization pointers 
would all be welcome.

thanks in advance!
mona (akerb...@acuson.com)