Chris, Does this product have resistive voltage dividers that cross the isolation boundary, or something similar? Without know the specifics of your product, I can offer only a couple of suggestions.
I have seen cases where the hipot causes damage but and the product is in full compliance with the safety requirements. Hipot was never intended to cause damage and it is generally permissible to disconnect any transient suppression devices or feedback circuits that may otherwise interfere with the test. Good judgment must be used in opening these circuits while doing the test. You may find the entire hipot potential impressed across the circuit opening you created and often there is not enough spacing to isolate the test voltage. You get an arc over. The other concern is, if you must temporarily disconnect surge suppression devices, there has to be a quality check to insure that these devices are reestablished prior to shipment of the product. The other situation is where you may have a voltage divider string that experienced too much power during the test. Some safety standards allow you to drop the test time to a much shorter duration by adding 20% to the test voltage. The power dissipation is then minimized by time. -doug Douglas E. Powell Corporate Compliance Dept. Advanced Energy Industries, Inc. Fort Collins, CO 80535 USA From: Chris Maxwell [mailto:[email protected]] Sent: Thursday, August 28, 2003 9:45 AM To: EMC-PSTC Internet Forum Subject: Hi-Pot testing All, We have a product that runs from AC power. During safety testing at the lab, the unit passes HiPot testing. However, the unit is broken by the testing. Rigorously, the unit "passes" its type testing because it doesn't become unsafe by the Hipot. However, it isn't functional after the test; and it requires repair. The unit does meet surge test requirements. (EN 61000-4-5, Class II). The unit has surge protection circuitry installed from line to earth (MOV in line with a gas tube). This surge protection is disabled before the hipot test. So, here are a few of my random thoughts on this process. 1. I can't break every unit by hipot testing it before I ship it. 2. When the unit is in the field, it will have the surge protection installed, which will essentially limit any "real life hipot" voltages to about 500V (230V gas tube, 275VAC MOV). In real life, the unit would experience a maximum 500V hipot. However, in the case of a single fault (surge protection disabled), the unit could experience higher hipot voltages, which would cause damage, but not an unsafe condition (as shown by type testing). 3. The surge protection is not easily removed for hipot and then reinstalled after hipot. So...are there any alternative test or inspection methods that can be used on this product? Thanks in advance, Chris Maxwell | Design Engineer - Instruments Group email [email protected] | dir +1 315 266 5128 | fax +1 315 797 8024 NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA web www.nettest.com | tel +1 315 797 4449 | 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: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc _______________________________________________________________ This message, including any attachments, may contain information that is confidential and proprietary information of Advanced Energy Industries, Inc. The dissemination, distribution, use or copying of this message or any of its attachments is strictly prohibited without the express written consent of Advanced Energy Industries, Inc. 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: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
