According to
https://www.macromatic.com/blog/relays/what-are-pilot-duty-ratings-and-which-macromatic-products-have-them “A pilot duty rating is a contact rating intended for contacts that control the coil of another relay or contactor. These ratings are applicable when controlling loads like relay coils, contactor coils, solenoids, and other similar inductive loads. Contacts with a pilot duty rating have passed standardized testing to prove they can reliably control a pilot duty load. The highly inductive nature of pilot duty loads is hard on contacts; controlling pilot duty loads using contacts not rated accordingly can cause premature failure and improper contact operation.” Since you are driving a contactor with a solid-state relay, there are no physical contacts. So, it seems to me, the solid-state relay need not have a pilot duty rating. But, the device must withstand the inductive kickback when the circuit is opened. The zener reduces the kickback. But, there is no outward sign when the zener fails open, so the solid-state relay must be capable of withstanding the kickback. UL only applies the standard. UL folks seldom apply their engineering skills to a certification as the EUT must comply with the standard. Differing from the standard requires review by at least one engineer or manager. You must build the case and show the UL folks how the EUT meets the “intent” of the standard. Good luck! Rich Ps: Thanks, John, for the hint of a web search. From: John Woodgate [mailto:j...@woodjohn.uk] Sent: Thursday, December 7, 2017 2:00 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Pilot rating A web search for 'OPTOMOS pilot duty rating' produces useful information, including references to UL508. But it seems that these are contact ratings for switching inductive loads (other relay coils). Since you have the double zener to absorb the inductive kick, you would only need, it seems, the opto to have pilot rating if the zener fails open-circuit. John Woodgate OOO-Own Opinions Only J M Woodgate and Associates www.woodjohn.uk <http://www.woodjohn.uk> Rayleigh, Essex UK On 2017-12-07 21:45, Jon Keeble wrote: We are getting a somewhat innovative product through UL at the moment. So there has been quite a lot of discussion and feedback from UL. But when UL said they thought my little board needed a pilot rating I really thought they were joking. Jon Keeble From: Jon Keeble [mailto:j...@wattwatchers.com.au <mailto:j...@wattwatchers.com.au> ] Sent: Thursday, December 7, 2017 12:29 PM To: EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: [PSES] Pilot rating I am using a Panasonic AQH3213A PhotoMOS optical isolator to control a small contactor. At 110VAC the contactor coil draws 30mArms. The coil contacts are wired to a PCB via a terminal block plug and socket. On the PCB is a series 10ohm fusible resistor, and a SMBJ400AC bidirectional zener. When the switch opens at peak current (42mA) there is 0.1J of energy in the coil that gets absorbed by the zener. The zener * clamps at a voltage way below the voltage rating of the optoMOS switch. * is rated at 600W for 8.3msec and is subject to only 13W for a similar period. The UL test engineer says that the optoMOS should be "pilot duty" rated (the part I am using does have this rating). Does anyone know what triggers the requirement for a "pilot duty" rating? Is this defined in a standard somewhere? This useful link identifies "contact rating codes" https://na.industrial.panasonic.com/blog/what-pilot-duty-rating-how-it-obtained The lowest rating E300 is for 110V 1.8A (make) 0.3A (break) Technically speaking, my switch is not connected to the contactor .. there is a two-component network in between Does UL have the capacity or procedures in place to understand and accept a circtuit analysis that shows my circuit as safe? Jon Keeble Wattwatchers. - ---------------------------------------------------------------- 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 <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
