That was what I thought, thank you all for confirming. However, with it connected red+/black-, when our tech flipped the breaker it blew out the DC/DC converter. In fantastic order, I was told. So I'm going to have them put a voltmeter to the wires and see what we are getting from the power supply, maybe the output wiring is wrong.
-- Christopher Tyler MTCRE/MTCNA/MTCTCE/MTCWE Total Highspeed Internet Services 417.851.1107 ext 9002 ----- Original Message ----- From: ch...@wbmfg.com To: "AnimalFarm Microwave Users Group" <af@af.afmug.com> Sent: Monday, April 8, 2019 11:59:47 AM Subject: Re: [AFMUG] DC/DC converter question What Ken said. Positive is always positive. Neg is always neg. 48 volts is 48 volts. If someone wants to say a load or source is -48 or +48 it just means the opposite polarity is tied to earth or chassis ground. If they say a load needs -48, it could mean that the load has the positive power wire also connected to the case. If a source says it is a -48 source, it could mean that the source has the positive lead connected to ground. You can always test a source. Ground to the wire. If you measure 48 volts between ground and one of the power wires, then it is referenced to ground. If you are on the positive wire to ground and you see 48 volts, then it is a neg ground system. If you are on the neg wire to ground and you see 48 volts then you are on a positive ground system. Positive Ground System == -48 or whatever volt system Neg Ground System == +48 or whatever BUT many sources and loads are floating where neither power lead is connected to chassis/earth/ground Sometimes they will call those 48 VDC system. But sometimes they will call them a +48 VDC system when really it is simply a 48 VDC system. Anytime -48 is printed on something, time to take it seriously. They probably mean it. -----Original Message----- From: Christopher Tyler Sent: Monday, April 8, 2019 9:54 AM To: AnimalFarm Microwave Users Group Subject: [AFMUG] DC/DC converter question I have a Meanwell SD-350C-24 DC/DC converter for +48v in to +24v out. I just learned that our DC plant at this site is -48vdc. I'm assuming that I can't just plug it in backwards. But we've never had to deal with -48vdc before, am I wrong in this assumption? -- Christopher Tyler MTCRE/MTCNA/MTCTCE/MTCWE Total Highspeed Internet Services 417.851.1107 ext 9002 -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com
