I have been looking at overload protection requirements for machinery, and I am a little unsure about application of branch protection versus supplementary protection. For example, suppose a machine is powered from AC mains (single phase or 3-phase, I don't think it matters). The power entry to the machine contains a main disconnect (breaker). The AC power is then distributed within the machine to power supplies, motor controllers, and internal-only outlets. These internal outlets are used during installation by trained service personnel for defined auxiliary devices and are accessible behind tool-accessed covers, not intended for operator access. Each internally distributed circuit is further protected by a overcurrent device (breaker) in addition to the main disconnect breaker. Individual motors have further overcurrent protection. The machine installation requires the customer to provide a dedicated circuit of sufficient capacity for the machine, with a nearby disconnect.
Questions: If the facility disconnect is a UL 489 listed circuit breaker that meets the requirements for branch protection, are we required to have additional branch protection within our machine or is supplementary protection sufficient? If we do need branch protection in the machine itself, is it sufficient only for the main disconnect at the power input? Are there differences in the requirements for U.S. and Europe? Thanks. Jim Hulbert ________________________________ - ---------------------------------------------------------------- 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]>
