earth system 1

[aliorooji]

hi.I want to use an isolation transformer for a sensitive load.
(laboratory)also now we have an earth system.
can I use this isolation transformer and this earth system.
because isolation transformer can isolate input voltage with output voltage will not any problem occur with our earth system?
thank you very much.

 

[ScottyUK]

- You have a transformer, which we know nothing about.
- You have a load, which we know nothing about.
- You have an earthing system, which we know nothing about.

And to finish it off, we have no idea what problem you are trying to solve.


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If we learn from our mistakes I'm getting a great education!

 

[aliorooji]

our transformer has these characteristics :220 to 220 volt and 5 amp
we have a three phase system that we have provided our 220 volt output voltage from this system with a null wire.
we want to install a immunology system.the factory which has made this system said to me that you should provide an earth system which provides a safety ground.we did this job.now voltage between null and earth is approximately 6 volt(when all consumers are on).
now I want to use isolation transformer to provide 0 or less than 2 volt(earth-null).I want to connect an output of transformer to ground.is this good?
thanks.

 

[waross]

I don't have time to check my medical standards just now for values, but a system that has been used for medical safety has been isolation.
1: The transformer must have a grounded safety shield between the primary and the secondary windings.
2: The voltage that you see to ground from each line will depend on the impedance of the meter.
3: The important parameter is the leakage current from either line to ground. This must be a very low value that will probably be specified in your governing regulations.
4: STRONGLY consider purchasing a commercial isolation unit with automatic self testing and a guaranteed acceptably low level of leakage current.
This function may be included in the factory supplied device. Consult with the factory as to the connections for the isolation transformer.
You may need only a ground conductor but we can't tell without a lot more information.
This may be a life safety issue. Check with the factory, the local electrical inspector or hire a consultant with experience in this field.
I hope we have shown you the way to find your answers but we can't and won't say what you should do without a lot more information.

Bill
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"Why not the best?"
Jimmy Carter

 

[7anoter4]

The single phase loads in a 3 phases supply system produces an unbalance of the loads. If the neutral is broken and not well grounded close to the consumer the phase to neutral voltage could be at dangerous level- up to phase to phase voltage-if the consumer phase load is low[ high impedance] and the other phase load is high[low impedance]. A good neutral grounding has to reduce the difference between neutral and grounding wire and to equilibrate the voltages.
The isolation transformer -taken all the precautions described by waross - will reduce this danger, but the touch potential will remain the same if you'll ground one of the secondary lines. Usually the isolation transformer serves to insulate both exit lines from earth - up to some thousands megohms- and so to reduce the current through the human body. A good insulation surveying has to be provided indeed.