Joe, The situation which you describe is absolutely a failure. If you doubt this (and I am not trying to be flip) try using two fingers (OF THE SAME HAND!) instead of the meter. This is what your customers might experience. If you have that much capacitance to hold a charge at that level after five seconds you need to do something about it. I would start by tracing out the wiring. Normally the switch should isolate the unit from the line, especially if a double pole unit is used. It sounds like a wiring error.
I once saw a design engineer get a 6kV jolt through the hip from a unit equipped with safety interlocks that had accidently been bypassed during a wiring change. He was leaning against the frame with the interlocked(?) covers removed. If all else fails, I would suggest a bleeder resistor across the capacitance, adding a relay to isolate the line cord from the capacitance, or something of that nature. It would be normal for the unit to be switched off before being unplugged. 100 plus volts across the pins could be very unpleasant. Best Wishes Scott B. Lacey -----Original Message----- From: [email protected] [mailto:[email protected]]On Behalf Of [email protected] Sent: Friday, May 11, 2001 12:31 PM To: [email protected] Subject: Capacitor Discharge Test We evaluate our laboratory equipment to UL 3101-1, CSA 1010.1 and EN 61010-1. Section 6.10.3 of UL 3101-1 states "If plug pins of cord-connected equipment receive a charge from an internal capacitor, the pins shall not be HAZARDOUS LIVE 5s after disconnection of the supply". We have always performed this test with the power switch in the ON position and would have the unit running then unplug the power cord and take our reading on the oscilloscope. We have never measured any voltages above the HAZARDOUS LIVE limits of 30Vrms, 42.4V peak or 60Vdc. Our new NRTL Engineer has now also requested us to perform this test with the power switch in the OFF position. With the switch in the off position our voltages after 5 seconds are close to line voltage. The NRTL is considering this a failure. However, UL 3101-1 also states in Section 6.10.3 "For plugs receiving a charge from an internal capacitor, the measurements of 6.3 are made to establish that the levels of 6.3.1.3 are not exceeded." 6.3.1.3 requires measuring the overall capacitance from the unit. Our NRTL states that there is no method available to measure the overall capacitance of the unit. Has anyone else in the group had any experience with this issue? Does your NRTL require testing with the switch in the OFF position? Do your units fail with the switch in the OFF position? Is it a failure just because the voltage limits are exceeded, or is it only a failure if the current and capacitance limits are exceeded. (Similar to the Permissible Limits Requirements). Have you had any experience with NRTL's not being able to measure the overall capacitance? All responses are greatly appreciated. Regards Joe Martin Applied Biosystems [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.rcic.com/ click on "Virtual Conference Hall," ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.rcic.com/ click on "Virtual Conference Hall,"
