Bill writes: It's been my (EU) interpretation that in satisfaction of the Low Voltage Directive, the scope of the Safety of Machinery standard (EN60204) applies to equipment with at least one moving part. My employer designs electrical equipment (power supplies) in which there are no moving parts. Thus, I've selected and have been reading EN61010 as our safety standard.
We provide a circuit breaker (ON-OFF), a power off button (function START-STOP) and a safety-interrupt loop connection (<24Vdc) which is available for the user to attach their OFF switch; each of these methods halt power output. I see no explicit requirement for an embedded or built-in EStop under EN61010; does anyone else interpret this differently?> Hi Bill. 61010 really relates to laboratory or instrumentation, while 60204 relates to Production Equipment, the semantics being that 61010 implies that the users will be skilled in the use of the equipment, and that 60204 has to assume that the users will have no idea what or where the unit is. My own approach to such matters has been to ensure that the equipment is safe in single fault situations, Much of my history has been with supplies driving critical potentially unsafe mechanisms, high pressure hydraulics, motors etc., and high voltage supplies, 19" rack stuff, used in analytical and process development applications, where I've interlocked High Voltage connectors (50kV@ 100mA). I've always designed these systems such that only when connected both ends does the output go live. In the same interlock chain I've placed an 'Emergency Stop' button, on the PSU front panel and at the process end as well. The interlock and ES button have been dual positive break switches, separately wired, going back to two contactors, one coil in each circuit, with the power contacts in series. These were wired so that in order to run the PSU, the contactors had to be latched, or 'armed', i.e. energised, such that any connector being unplugged, or an ES button being pressed dropped out the contactors. Two contactors to provide single fault redundancy, and the arming circuit wired through both contactor auxilliary N/C contacts, wired in series - such that if a contactor was stuck closed the circuit wouldn't arm. Also, a lamp was wired through other auxiliary contacts on the contactors, N/O on one and N/C on the other, in two circuits, so as to light a lamp when a contactor was stuck closed. All that functionality is also available in 'safety relays' with guided contacts and redundant power connection but at a cost. The esential difference with your situation is that though it was 61010 equipent, the PSU's, or uncontrolled hydraulics etc., were killers in their own right, so I reckoned that regardless of regs, I really didn't want to explain to someone that their partner was dead, but that our equipment met the standards ok. Does any of that make sense.. A picture would be much easier. Chris Dupres. *******************Internet Email Confidentiality Footer******************* The contents of this e-mail message (including any attachments hereto) are confidential to and are intended to be conveyed for the use of the recipient to whom it is addressed only. If you receive this transmission in error, please notify the sender of this immediately and delete the message >from your system. Any distribution, reproduction or use of this message by someone other than recipient is not authorized and may be unlawful. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html 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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
