208v to 120/240v

Besoeker3 said:
One of the posters here called it an RV or a Caravan which is similar for the UK version. We wouldn't have used the in a house. C'est la vie.
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I don't think you are understanding. The RV has a house/breaker panel IN IT that is similar to the breaker panel IN a house.
By similar, I mean the 50A RV panels have a 240V supply, but all the loads are 120V. The 240V supply just gives them more available 120V loads.
The 30A RV panels only have a 120V supply.
RV=Recreational Vehicle
 
Little Bill said:
I don't think you are understanding. The RV has a house/breaker panel IN IT that is similar to the breaker panel IN a house.
By similar, I mean the 50A RV panels have a 240V supply, but all the loads are 120V. The 240V supply just gives them more available 120V loads.
The 30A RV panels only have a 120V supply.
RV=Recreational Vehicle
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Yes, I know what an RV is. The confusion was in the domestic residence rather than RV. They are two things.
 
winnie said:
In this polyphase case, I simply mean that the primary circuit and secondary circuit share some of the coils and that there is no galvanic isolation from primary to secondary. So you can have coils of different phases (coils on different cores) electrically in series.
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So how's this for a broader definition of autotransformer: there is a copper path (including transformer coils) from every output side conductor to an input side conductor? I agree your proposed arrangement meets that definition.

Also, does galvanic isolation mean "there are no such paths" or instead "any output conductor with such a path is grounded"? Or something else?

Cheers, Wayne
 
wwhitney said:
Also, does galvanic isolation mean "there are no such paths" or instead "any output conductor with such a path is grounded"? Or something else
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Isolated means isolated. This is the starting point.
However, the NEC requires bonding separatly derived 120V systems to ground. Which kind of negates total isolation. But the normal current carrying conductors are still isolated until a fault occurs.
 
wwhitney said:
Also, does galvanic isolation mean "there are no such paths" or instead "any output conductor with such a path is grounded"? Or something else?

Cheers, Wayne
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For transformers, I think a fair definition is 'galvanic isolation means there are no conductive paths between primary and secondary internal to the transformer. A grounding connection may create a conductive path outside of the transformer.' Or perhaps 'In a transformer arrangement with galvanic isolation, intentional grounding breaks the galvanic isolation between systems. In an autotransformer arrangement, there can be no galvanic isolation because transformer coils are shared between primary and secondary systems.'
 
winnie said:
In this polyphase case, I simply mean that the primary circuit and secondary circuit share some of the coils
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Do you mean this literally, as in if you draw the primary circuit (consisting of the primary supply equipment, some conductors, and some subset of the coils) and the secondary circuit (consisting of some subset of the coils, some conductors disjoint from the primary conductors, and the load equipment), then there is at least one portion of one coil that is common to both circuits?

In other words, say you have a 120V:120V transformer, and you supply the primary with L-N 120V, and the secondary terminals are L'-N' respectively, and you connect N' to L, so that L' is at 240V to N. If your secondary conductors are N and L' to make a 240V grounded 2-wire supply, that's an autotransformer. While if your secondary conductors are L' and N', that's not an autotransformer, you've just created a weird 120V 2-wire supply referenced to ground but with neither secondary grounded.

Is that the usual terminology?

Cheers, Wayne
 
Besoeker3 said:
Yes, I know what an RV is. The confusion was in the domestic residence rather than RV. They are two things.
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Here in the US due to housing costs for many an RV has become their domestic residence.
Back to the OP
I think we all agree you do not need a buck/boost
 
wwhitney said:
In other words, say you have a 120V:120V transformer, and you supply the primary with L-N 120V, and the secondary terminals are L'-N' respectively, and you connect N' to L, so that L' is at 240V to N. If your secondary conductors are N and L' to make a 240V grounded 2-wire supply, that's an autotransformer. While if your secondary conductors are L' and N', that's not an autotransformer, you've just created a weird 120V 2-wire supply referenced to ground but with neither secondary grounded.
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I don't know. It would seem very odd to create a 120V system that is itself 'floating' 120V away from ground and not include the voltage to ground as part of your 'system', and if you include the ground reference as part of the system then you clearly have an autotransformer.

But I agree, you've suggested a situation (2 wire secondary system, 120V and 240V to 'ground', that doesn't neatly evaluate as 'autotransformer or not' in my suggested system.

-Jonathan
 
winnie said:
I don't know. It would seem very odd to create a 120V system that is itself 'floating' 120V away from ground and not include the voltage to ground as part of your 'system', and if you include the ground reference as part of the system then you clearly have an autotransformer.
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Here is another tangent. In the UK, 'ealth 'n' soiftey wants you to run a transformer from 230 down to 110 center grounded (+/- 55V) on construction sites so nobody can electrocute themselves, since 55V to ground is almost a safe voltage. So that must mean that they have another voltage class for power tools over there, too.
 
Birken Vogt said:
Here is another tangent. In the UK, 'ealth 'n' soiftey wants you to run a transformer from 230 down to 110 center grounded (+/- 55V) on construction sites so nobody can electrocute themselves, since 55V to ground is almost a safe voltage. So that must mean that they have another voltage class for power tools over there, too.
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For UK (and EU) residential it is single phase 230V ac. That's it. For industrial we normally use 110Vac for power tools. I have seen some that are 55-0-55 AC. Then there industrial power systems that can almost any voltage. For example we have paper mills that are 700Vdc, cement works are 3,300 Vac, petrochem works at 11 kV, and arc furnaces at 132 kV. Just a few of the projects that my job required,
 
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