See below.
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK
On 2017-10-12 09:16, James Pawson (U3C) wrote:
Hi John,
OK this is getting interesting, I see your point on the distinction
for “conditions”. Would it specifically say “clauses” if it meant any
of the text in that section?
JMW: No, I think it would have to be completely re-written. It is rather
ambiguous: does 'above conditions' refer to a,b,c or to 'less than or
equal to 200 W or that the limits of Table 3 are not exceeded'. And in
b), it is not totally clear which limits are 'relevant', taking into
account what it says in Clause 5; 'Equipment not specified in one of the
three other classes shall be considered as Class A equipment.' Then in
Clause 7 '..limits are not specified in this standard..... professional
equipment with a total rated power above 1 kW', yet the flow-chart makes
that apply only if techniques not allowed in 6.1 are not used.
The 2014 edition of 61000-3-2 has been revised and the draft final
voting stage is expected to be approved for circulation at an upcoming
meeting of the committee. The chairman has invited me to submit a
document to that meeting (I cannot attend) explaining the confusion and
proposing a solution. The new draft is rather different from the 2014
edition, but at present anomalies still exist.
Taking this into account, for the equipment described:
So, the use of symmetrical control methods for professional equipment
is permitted if
1. The a|b|c conditions in 6.1 do not apply to the EUT (they don’t)
2. The limits are not exceeded and it is being used for precise
temperature control and there is no other technique available (not
being used for precise temp control)
This all hinges on whether it is using a control technique that is not
permitted under Clause 6.1.
I think that's clear; phase angle control is symmetrical and it does
produce low-order harmonics.
Or does the provision apply for symmetrical control methods which
produce large low order harmonics that are used to power heating
elements, in which case the harmonic limits of Table 3 apply?
Yes, if the product meets the Class D (Table 3) limits, it complies.
Does it? It might, because of the low duty cycle. Note that the 'mA/W'
figures relate to the 3 kW, not the actual RMS input current.
I suppose that even if we get all the way through the flowchart to the
end and it doesn’t meet the limits there is still a catch for
If (professional equipment) then apply Clause 4. This might be the way
forward.
It seems not sensible to apply Clause 4 to such a low power product. I
think many suppliers would laugh if asked for permission to connect. But
telling purchasers that they have to ask for permission would be a sales
off-put.
Round, like a circle, like a spiral…
JMW: If the product is installed on a springy dustfield on the Moon, no
limits apply, unless it's supplied by a mental wind turbine, since there
is no physical wind on the Moon.
I'll try to keep you informed on progress.
James
*From:*John Woodgate [mailto:j...@woodjohn.uk]
*Sent:* 11 October 2017 22:21
*To:* EMC-PSTC@LISTSERV.IEEE.ORG
*Subject:* Re: [PSES] IEC 61000-3-2 Confusion
That isn't a 'condition'. The conditions are the items in the a-b-c
list in 6.1.
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associateswww.woodjohn.uk <http://www.woodjohn.uk>
Rayleigh, Essex UK
On 2017-10-11 21:42, James Pawson (U3C) wrote:
It was the symmetrical control for the powering of heating
elements part that was the previous condition that was fulfilled.
Hope this helps
James
---- John Woodgate wrote ----
OK, I've sent a digest to the committee chair. Meanwhile, I
noticed something that I don't quite understand:
You say that "Clause 6.1 also says that symmetrical control for
professional equipment is OK provided one of the “above
conditions” is fulfilled (which it is, see previous bullet)"
Which is the 'above condition' that the welder meets?
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associateswww.woodjohn.uk <http://www.woodjohn.uk>
Rayleigh, Essex UK
On 2017-10-11 17:08, James Pawson (U3C) wrote:
Hello John,
It uses phase angle control hence the concern about the
harmonics generated.
Manufacturer specs are single phase, 230V nominal, 3kW.
Typically used at less than a 15% duty cycle, often less, in
an industrial environment or powered from a generator.
My *feeling* is that should be classified as professional
equipment and exempted under Clause 7 but the IEV has 0 search
for feelings.
Thanks for your help
James
*From:*John Woodgate [mailto:j...@woodjohn.uk]
*Sent:* 11 October 2017 16:49
*To:* EMC-PSTC@LISTSERV.IEEE.ORG
<mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
*Subject:* Re: [PSES] IEC 61000-3-2 Confusion
I agree that there appears to be a need for clarification, and
I will take that up with the committee responsible. But for
your particular case, what is critical is the nature of the
'triac control'. Is it phase-angle control, or 'burst firing'
or something else?
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associateswww.woodjohn.uk <http://www.woodjohn.uk>
Rayleigh, Essex UK
On 2017-10-11 15:01, James Pawson (U3C) wrote:
Hi folks,
I apologise as I seem to be all take and not much give on
this forum at the moment; I’m trying to do a lot of
learning very quickly. Someone ask a question about HDMI
so that I can feel useful!
Today’s question is what appears to be a contradiction in
IEC 61000-3-2:2014.
·The customers equipment is a triac controlled high-power
PSU for welding plastic parts together using resistance
heater coils
·Power is over 1kW and the customer is suggesting that it
is “professional equipment” which, according to Clause 7,
means that harmonic “limits are not specified in this
standard”
·Flowchart in Clause 7 says that Clause 6.1 for allowed
control methods still applies even to equipment with no limits
·Clause 6.1 says symmetrical control methods which produce
large low order harmonics (arguably this applies to triac
control) that are used to power heating elements
(applicable) provided that either input power is less than
200W (it isn’t) or the harmonic limits of Table 3 apply
·Clause 6.1 also says that symmetrical control for
professional equipment is OK provided one of the “above
conditions” is fulfilled (which it is, see previous bullet)
So we’ve gone from Clause 7 saying no limits apply to
Clause 6 saying that Class D equipment limits apply.
However the flowchart in Clause 7 suggests that just by
being exempt from Clause 7 limits means it automatically
conforms to 61000-3-2
I feel like I’m going in circles. Does anyone have any
insight that might help?
Much appreciated,
James
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