Conformity - November 2008 - (Page 49) an application time of one minute, with a minimum limit typically 400 Mohms or (40 Mohms*m2)/Area(m2) IEC 61646 2nd Ed. - 2008 The specific standard for thin-film terrestrial photovoltaic modules is IEC 61646. This standard requires the same safety tests to the base standards of IEC 61730 and UL 1703. Inverters Devices such as inverters, converters, charge controllers and interconnection equipment that convert DC to AC also have to have Hipot and Ground Impedance testing. UL 1741 and IEEE 1547 cover inverters and other equipment. For products that employ power connectors, those connectors are normally investigated using UL 498, Attachment Plugs and Receptacles, and/or UL 1977, Component Connectors Used for Data, Signal and Power Equipment Applications. Note that electrical connectors must be certified for outdoor use in wet locations with exposure to sunlight (i.e., UV exposure resistant). If a customer should choose to create a listed power connector for use with photovoltaic modules and panels, also note that these devices must be designed robustly enough to withstand use as a DC circuit interrupt device under overload conditions, as outlined in UL 498 and UL 1977. UL 1741, Inverters, Converters, Controllers and Interconnection System Equipment for use with Distributed Energy System, covers a variety of devices used in conversion of electricity from a variety of sources, including fuel cells, photovoltaic, and wind energy systems, to another form of electricity for both grid and non-grid connected systems. This standard is to be used in conjunction with and to supplement IEEE 1547, Interconnecting Distributed Energy Systems with a Power System. IEEE 1547 covers general requirements, such as voltage regulation, synchronization, integration of grounding, monitoring and isolation, to manufacturing and commissioning tests. UL 1741 1st Ed. – 1999 Testing Dielectric Withstand testing is required both for compliance and production testing. The dielectric withstand is applied between input and output wiring to accessible dead metal, and between input and output wiring to accessible low voltage and limited energy parts including terminals. Test voltages for Dielectric Withstand testing are based upon rating voltage. Products with a 250V or less rating are tested at 1000VAC for 60 seconds or 1200VAC for one second. The equivalent DC can be used if the product can be damaged by AC potential. Products rated over 250V are tested at 1000VAC + 2 x rated voltage for 60 seconds, 1000VAC + 2.8 x rated voltage for one second, 1400VDC + 2.8 x rated voltage for 60 seconds, or 1700VDC + 3.4 x rated voltage for one second. The equipment for Dielectric Withstand testing shall have a visual indication that high voltage is being applied, visual and/or audible indication of failure, and manual reset switch in the event of failure. If the tester has a transformer less than 500VA, there must be a voltmeter in the output. Testers with a transformer of 500VA or greater shall have a voltmeter, indicating voltage selector or visible marking indicating output voltage. Ground Impedance testing is required in compliance testing. The equipment ground to any other metal part that is required to be grounded shall not exceed 0.1ohms. The impedance is measured at 25A and a frequency of 60Hz. The open circuit compliance voltage shall not exceed 6V. Robert M. Brown is the vice-president of technical operations at QuadTech Inc., and can be reached at rbrown@quadtech.com. References • UL1703 3rd Ed. – 2002 • CSA 22.2 No. 0.4 – 2004 • UL 1741 • UL 391 4 Ed th • www.mainewoodfurnaces.com • www.solarbuzz.com • www.futronics.co.uk • www.harmonstoves.com • www.evergreensolar.com • UL 1482 5 Ed th FAST Link www.conformity.com/2360 November 2008 CoNformity 49 http://www.mainewoodfurnaces.com http://www.solarbuzz.com http://www.futronics.co.uk http://www.harmonstoves.com http://www.evergreensolar.com http://www.conformity.com/2360 http://www.kikusui.us http://www.kikusui.us
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