Voltmeter. Have it all wired up but sitting on an insulator. Wood, cardboard box etc. Be good to put a load on it. Some rectifiers don’t really do their thing without a real load. 40 watt 120 VAC light bulb will work just fine. 360 ohms. 155mA @ –55 VDC.
Check to see if there is a voltage from the chassis to either output. Hopefully they are just floating. If you see a solid –48 to –55 volts from the negative terminal to the chassis, you have a non isolated rectifier. In that case you will have a problem because you will have to isolate the AC ground too and possibly the neutral as well. From: Gino Villarini Sent: Tuesday, December 08, 2015 9:41 AM To: [email protected] Subject: Re: [AFMUG] Isolating a -48 rectifier? How do i perform a galvanic test? On Tue, Dec 8, 2015 at 10:24 AM, Chuck McCown <[email protected]> wrote: The designer may or may not have tied the positive output to the chassis. You would have to galvanically isolate it and see if there is a voltage from negative to chassis. You might be OK or you might have to isolate it from the rack. If you do isolate it, make sure to put a sign on it that it is hot so someone does not lay a tool on it or touch it with a metal ladder etc that could ground it out and cause lots of sparks. I personally don’t feel –48 unless I am hot and sweaty, so to me it is not much of a shock hazard but may be for others. If you do isolate it, remember that the input AC probably has a ground wire that will tie the chassis to earth ground. If the +48 is tied to the chassis, you are going to have to disconnect the input ground too. And it is slightly possible, in an old and lousy design, that the AC neutral could also be tied to the chassis. From: Gino Villarini Sent: Tuesday, December 08, 2015 4:12 AM To: [email protected] Subject: [AFMUG] Isolating a -48 rectifier? So, i was wondering if isolating a -48 dc rectifier from the rack/ground would turn it into a polarity agnostic device?
