whartHi Bill,
2,018 posts
04-10-2019 9:42pm
I have used isolation transformers in a variety of settings. One, an old 240/120 step down made by Richard Gray for a big home theatre system- the system itself is long gone- was the only thing that would fully isolate a nasty electrical snap from the air compressor motor that energizes one of my tone arms. I now have a better electrical set up and a dedicated line wired to the regular house main electrical system set up for 20 amps for the air compressor. I use one of those Tripplite 1800 watt jobs. In speaking with the tech at Tripplite before I bought it, the secondary is bonded, it is not really floating. There’s at least one reference to this that I saw on the web, so I am not sure their claim of ’medical grade’ is fully accurate, at least insofar as a floating ground on the secondary.
The Richard Gray PDU (Power Distribution Unit) is wired as a "Grounded Power System". The neutral leg, lead, of the secondary winding is intentionally bonded to ground, as well to the metal enclosure of the unit. All equipment grounding conductors from the power outlets connect to this common point. Star grounding.
It also sounds like the secondary winding of the Tripplite 1800 isolation transformer is also wired as a Grounded Power System.
Your 10Kva isolation power transformer secondary winding is also wired as a Grounded Power System.
Below are two isolation transformers.
The first one floats the secondary winding above ground. Neither ungrounded conductor has any reference to ground. It doesn’t have any reference to the equipment ground contact on the receptacle outlet either.
The second example bonds one of the secondary legs to ground making it the grounded conductor, the neutral conductor.
Isolated Power System
https://www.tripplite.com/isolator-series-120v-1000w-ul60601-1-medical-grade-isolation-transformer-4...Offers line isolation and continuous noise filtering Internal low-impedance isolation transformer with Faraday shield offers 100% isolation from the input AC line Full UL 60601-1 medical-grade listing with hospital-grade plug and outlet receptacles for the protection of sensitive electronic equipment in patient-care areas Reduces cumulative leakage current of the Isolator and connected equipment to levels less than 100 μA Floating AC output prevents noise coupling from noisy hospital ground circuits and meets agency requirements
Grounded Power System
https://www.tripplite.com/isolator-series-120v-1000w-isolation-transformer-based-power-conditioner-4...Tripp Lite Isolator series isolation transformer-based power conditioners offer complete line isolation, continuous noise filtering and enhanced common mode surge suppression Supports combined loads up to 1000 watts continuous/8.3A at 120V Isolation transformer with Faraday Shield offers 100% isolation from the input AC line Neutral to ground bonding at the secondary eliminates common mode noise and provides an isolated ground reference for sensitive equipment
Jim
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