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#1
Start by
Aamir
09-05-2013 09:31 PM

Transformer electricity path

If we use Transformer of 220v to 220v after KWH meter for domestic use electricity & rest of household system supply through transformer secondary terminals.
My question is, if I touch phase terminal direct & path will complete through earth (not transformer neutral terminal), what would you say electricity path will complete or not. (I will burn out or not).
Need your comments plz.
09-05-2013 09:31 PM
Top #2
Norman
09-05-2013 09:31 PM
Your question is not clear so here is the best answer
It is said that the surface of the human body has a resistance of 10,000 ohms if dry. so if your body is properly insulated the floor or the general mass of earth, namely wearing a properly insulated shoe and you happen to touch a live conductor, it is not likely for you to have an electric shock.
09-05-2013 09:32 PM
Top #3
Aamir
09-05-2013 09:32 PM
actually my question is, if we use a transformer on house electricity line, it is necessary to use that transformer neutral point for circuit path complete or earth/ground can be used as neutral.
"one my friend said, he installed a trafo after KWH meter of his own house & when he touch phase terminal by hand & his feet touches to earth but didnt feel any shock, moreover no safety measure or tools he used."
he said if we use that trafo neutral point only way to effect from shock.
09-05-2013 09:32 PM
Top #4
Norman
09-05-2013 09:32 PM
This is not a safe practice do not follow suit. you might not be lucky
09-05-2013 09:33 PM
Top #5
Ghosh
09-05-2013 09:33 PM
What your friend is using is a 1:1 isolation transformer.When the neutral is not grounded there is no path for the current to flow from the phase to the neutral through your friend's body, so no electrical shock. Electric shock will happen only if neutral neutral is grounded in this case or when the phase and neutral is touched simultaneously.
However as Norman has mentioned it is not a safe practice. Don't try this at higher voltages
Treat electricity with respect
09-06-2013 10:00 PM
Top #6
Aamir
09-06-2013 10:00 PM
Sir,a little bit clearance is required. yah thats right my friend is using 1:1 isolation transformer & neutral point of transformer not grounded but circulated through home wiring for current flow (path completion).
transformer neutral not grounded but my friend touched phase of trafo & obviously his feet touched to earth (floor of his home that is also consider a ground point in term of electricity for current path completion).
either now current will flow through my friend body or not?
Thanks is advance.
09-06-2013 10:01 PM
Top #7
Norman
09-06-2013 10:01 PM
Yes it is very critical that it be used, it is the reference point for singe phase loads and is also the low impedance reference point for a short circuit
09-06-2013 10:01 PM
Top #8
Chris
09-06-2013 10:01 PM
you need to confirm if that floor has the same potential as general mass of earth. Simply test with your instrument (meter) and not your body!. Your friend could have been standing on an insulated floor. Please don't toy with electricity if you are not technically sound to make informed decision on it. Follow your safety rules.Remember it doesn't give one a second chance to correct one's mistakes!
09-06-2013 10:02 PM
Top #9
Sudip
09-06-2013 10:02 PM
Ground is at zero potential?
Potential is only relative and ground as zero potential is for reference purpose only.In this case if you measure the voltage between the phase wire and any ground condutor in your home you will not measure any voltage in the multimeter.
Its a myth that current will flow back to the ground .Actually the current will flow back to the source only , the ground can provide a path for the current to flow back to the source depending on the fact that the source is grounded or not.As the neutral is not grounded the current cannot flow through the ground in this case and hence no electrical shock
09-06-2013 10:03 PM
Top #10
Doug
09-06-2013 10:03 PM
There are uses for isolation transformers. When I was getting started in electronics (in the Vacuum Tube/Valve days) many small radio and intercom kits were "Hot Chassis" where the B- was one side of the AC main -- 120V in the USA. Also most "All-American Five" AC/DC consumer electronics (AM/FM radios, record players, etc.) had the same wiring to save the money and weight of the transformer. For trouble-shooting this equipment, it was safer to use an isolation transformer to help keep from frying yourself. In Europe, many hotel bathrooms have a low wattage "Shaver Outlet" which is most likely an isolation transformer so you don't electrocute yourself if you drop your electric razor in the sink. Because it is a transformer, most of them have a center tap for 110volts as well as the usual European 220v.

Today, the usual domestic safety device is the Ground Fault Interrupter [GFI] that senses a few milliamps and opens the power circuit. In most electrical codes it is required in Bathrooms, Kitchens, outdoor outlets, basements, garages, and other places with water pipes or other things that are firmly grounded. In the USA, domestic GFIs must trip at 10mA to ground, commercial/industrial at 25mA (I think).
09-06-2013 10:03 PM
Top #11
Norman
09-06-2013 10:03 PM
Sudip, please check and review your comment in para 2. urgently. we will take it that you have made an error. if all your appliances including your transformer double insulated, which means, there are no physical conductive path to the surface which is a part of the general mass of earth, then your statement may be true. but in the real world which i am living; it is not so. plz verify your statement.
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