RS Isolating Transformer

[Bushbaby]

Hi Lawerence,
I would take it that all is strapped to earth.

Regards

Rob

[pwdrive]

Hello Rob, as mentioned in one of my previous posts I am not a qualified electrician, but appart from the normall precautions when servicing stuff containing voltages/currents that have the potential to kill then I have always regarded the protective earth as supplied by the electricity distributor as my true safety earth so all the equipment on my bench wether it be receiver or test gear or any combination of either/or have their chassis connected to this same earth, that being the supply earth ie all the chassis are are at the same 0 volts potential so to speak.
Anything that has the means of producing a floating chassis rail on my bench is a no no.
Ok... confession time... I do not have an isolating transformer at present, hence that is why I am extra cautious as regarding earthing especially considering the age and condition of some of the kit that ends up on the bench, in particular old power supplies with "y" configured mains filter caps or transformers that are prone to leakage.
I have B40D receiver that occasionaly trips the RCD on the supply, it does it because the filter caps. are on the way out and the fact that I earthed the receiver to the suppliers protective earth, if they totally break down then the trip will cut out perminantly, if the receiver was not earth connected the chassis could then become live with respect to earth under that fault condition and thus present a potential shock hazzard irespective of wether a supply RCD is fitted or not.
When I do obtain a suitable Isolating transformer I will connect it like it says in the guide posted as I have worked in workshops in the past where that method was used. Plus when using test equipement there is always a common earth for referencing.

Lawrence.

[Bushbaby]

Hi Lawerence,
Thanks very much for the info. I'm no electrician either but being a safety professional I always heed other peoples advice when it ensures my own personal safety.

Rob

[tiv48]

hi rob that looks like a very usefull transformer apart forom being able to run your usa stuff on one set of windings (as an ordenary step down transformer ) you could connect both secondries in series to create a 240 volt isolating trasformer for good old british/irish ac/dc sets .earth the metal work of the transformer. our practice was to have all test gear earthed
and run the sets from isolating tx, this became a nessessary when tv sets started to use bridge rectifiers chassis always live
rob t

[Skywave]

Hi Rob,
To sum up ~
As far as electrical safety is concerned, I consider that you won't go far wrong if you keep to 2 basic principles:
1. All exposed metalwork of all items must be connected to the incoming mains supply earth.
2. If you will ever be working on any a.c. / d.c. equipment, power each such item from its own dedicated isolation transformer.

'Refinements', such as RCDs, are indeed worth adding to any layout, but not absolutely essential, in my opinion. Many of us survived for years prior to their widespread introduction.

Al.

[Bushbaby]

Hi All,
Thanks for your valued input and help.
Would I be able to connect both secondaries for 240v and then operate one set of secondaries for 110v (can I assume that I this is the case)??

Rob

[tiv48]

yes rob
if it was mine i would build it into a box with a 13 amp socket and an american socket
rob t

[Bushbaby]

Hi Rob,
Good and many thanks!


Rob

[Skywave]

Would I be able to connect both secondaries for 240v and then operate one set of secondaries for 110v ??

Rob

Yes; as per the drawing below:

[attachment=3767]

Note that the dots on the two secondary windings denote that these two ends are in phase.

Al.

[Bushbaby]

Al,
Spot on sir and thank you. I take it then I need to add the inline fuses.

Rob