Dear John, Thanks for your comments. I have some below results of further investigation to share with you.
On Mon, 6 Nov 2023 at 22:22, John Woodgate <[email protected]> wrote: > I put some comments below. > On 2023-11-06 14:08, Scott Xe wrote: > > Last week, we received a sample of an induction hob from a supplier. The > unit is fitted with a 3-core power card and does not have a class II > symbol. The earthing core is terminated at a small copper pad on the > printed circuit board with a protective ground symbol (IEC 60417 - 5019) > next to the terminal. It is shocking to note that the copper pad is > standalone and not connected to the unit circuitry. We made an inquiry to > the supplier and replied that the product was designed by the engineer who > left the company. > > *JMW: That alone should indicate that you should have nothing to do with > the product, unless you are a test house, paid for assessing its safety.* > SX: According to the circuit diagram, the PCB missed out a resistor connecting between 2 capacitors and the isolated earth pad. The earthing path is for EMC compliance and the earthing is considered as a functional earth. The 2 capacitors must be Y1 class to fulfil safety requirements. > > I have two questions regarding the appliance. Firstly, can it be rated as > a class 1 appliance? > > *JMW: If it passes all the safety tests for a Class 1 appliance, it is a > Class 1 appliance. But it remains a suspect design.* > SX: Obviously the appliance does not rely on extra earth protection against electrical shock. The live parts must have double or reinforced insulation in order to meet class II requirements. > > Secondly, what are the main purposes of installing a 3-core power cable > that has no obvious functionality? > > *JMW: There is a strong temptation to do that if it's too difficult to > meet the Class II requirements.* > SX: The earth core is used for grounding the interference. > > > Additionally, while examining the PCB layout, I noticed punched holes for > a resistor and two capacitors connected in series, with the capacitors > connected in parallel first. Currently, there are no components present in > those holes. I would like to know if these components are necessary for EMC > compliance. > > *JMW: There is no way anyone can advise you on that, even if we could see > where the 'missing' components appear in the schematic. You have to test it > as it is and see whether it meets the EMC requirements.* > SX: It is a common practice for oem manufacturers to design a product embedded with the requirements of many customers. The actual no of components is subject to individual customer requirements. It is likely to cause confusion and/or miscommunication to the sample preparation team. > > > Your advice is appreciated! > > > Thanks and regards, > > > Scott > > > > > ------------------------------ > > This message is from the IEEE Product Safety Engineering Society emc-pstc > discussion list. To post a message to the list, send your e-mail to All > emc-pstc postings are archived and searchable on the web at: > https://www.mail-archive.com/[email protected]/ > > Website: https://ewh.ieee.org/soc/pses/ > Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to > unsubscribe) <https://ewh.ieee.org/soc/pses/list.html> > List rules: https://ewh.ieee.org/soc/pses/listrules.html > > For help, send mail to the list administrators: > Mike Sherman at: [email protected] > Rick Linford at: [email protected] > > For policy questions, send mail to: > Jim Bacher at: [email protected] > ------------------------------ > > To unsubscribe from the EMC-PSTC list, click the following link: > https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1 > > - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: https://www.mail-archive.com/[email protected]/ Website: https://ewh.ieee.org/soc/pses/ Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to unsubscribe) List rules: https://ewh.ieee.org/soc/pses/listrules.html For help, send mail to the list administrators: Mike Sherman at: [email protected] Rick Linford at: [email protected] For policy questions, send mail to: Jim Bacher: <[email protected]> _________________________________________________ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
