I encountered a problem with power supply a few years back. It would haply run across a wide range of input voltages, phase to neutral or phase ot phase, it did not really care. Apart from one little capacitor sitting in the EMF noise filter. It was polarized and only happy if the Phase and neutral were the correct way around. The effect of reversing the polarity was harmonic distortions with measured current harmonics upto the 39th order. Also the immunity to the line noise changed, changing form happily shaking of a 3kV surge, to watching the boost caps explode at a 2kV surge. Would run with either terminal connected to the phase, but a whole new emc profile. The standard offering had this capacitor, the USA version did not. Only difference on the power supply, two letters in a 20 character part number. These little things do sometimes catch designers by surprise.
Doug McKean wrote: > From: <[email protected]> > > > > Another potential problem I see with calling both a phase-to-phase > > connection and a phase-to-neutral connection, "single-phase" is that > it > > presumes that all power supplies can be connected either way. What > if a > > vendor designs a system in which the power supply is changed many > times over > > the years? Can you be absolutely, 100% sure that any power supply > that you, > > or your successor, select will work with a phase-to-phase > connection? Would > > you bet your reputation on it? Would you bet your job on it? > > Uh, yes - I have many times and do with the products I've > worked on. That's part of my job responsibility. > > My original statement which may have been lost in translation > was the following - *IF* you can connect either as input, you > have a single phase system, AFAIC. > > Your examples are obviously valid if those are the issues at > hand. But, they are outside my point and do not contradict > what I originally said. If however these issues are surprises > in the course of someone's job, then of course there's > reason for concern. > > Regards, Doug McKean > > ------------------------------------------- > 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," -- Andrew Carson - Product Safety Engineer Xyratex Engineering Laboratory Tele 023 92496855 Fax 023 92496014 ------------------------------------------- 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,"
