Dear experts, Is anyone familiar with UL 1741? I am dealing with solar inverter for US market. Solar inverter can operate in utility interactive mode (feeding the grid) or in a standalone mode where only homeloads are supplied by inverter (anti-islanding relays are open, due to problems with the grid). When anti-islanding relays are open, I have an issue of grounding the neutral conductor of output for homeloads. How can this grounding be achieved? Clause 19.2 does not allow grounding inside the unit (or I have understood it incorrectly and it only prohibits fixed connection) and clause 19.3 requires that output is grounded. Below is extract from the standard. Any idea? I think it is the same issue as with UPS.
19.2 An inverter intended to be utility-interactive shall not have a direct/solid electrical connection between any output ac conductor and the enclosure. 19.3 Other than as specified in 19.2, each ac output circuit shall have a grounded conductor. The ac output circuit conductor to be grounded shall be as follows: a) Single-phase, 2-wire - one conductor. b) Single-phase, 3-wire - the neutral conductor. c) Multiphase system having one wire common to all phases - the common conductor. d) Multiphase system in which one phase is used as in item (b) - the neutral conductor. 19.4 The conductor specified in 19.3 is to be connected by a bonding jumper connected between the grounded conductor and: a) The enclosure of a metal-enclosed unit, or b) For a nonmetallic enclosed unit, the metal chassis that is bonded to the equipment grounding conductor or terminal. See 18.2.1. Thank you for your support. Best regards, Bostjan - ---------------------------------------------------------------- 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: 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
