Hello, James. Could you please answer the question below?
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK
On 2017-10-12 20:47, John Woodgate wrote:
I am bound to be asked another question. Why have a 3 kW heater if
it's always used with triac control at a firing angle of 153 degrees
or higher? Is it to get very rapid warm-up at full power, then
maintaining temperature will much reduced power?
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associateswww.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
*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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