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| <
[email protected]
| Phil Allison |
|
|> |
|> |> What would it take in the design of a UPS to make it work correctly and
|> |> safely
|> |> under conditions where the incoming power could have either wire
|> grounded
|> |> or
|> |> neither wire grounded (but there will always be a separate equipment
|> |> grounding
|> |> conductor), and will operate over the nominal voltage range of 200 to
|> 240
|> |> with
|> |> either 50 or 60 Hz input?
|> |
|> |
|> | ** The above question simply does not make any sense.
|> |
|> | Reversal of the active and neutral conductors is of no consequence in
|> the
|> | vast majority of AC powered devices.
|>
|> What about "grounded center", where 2 inverters working in sync in the
|> range of 100-120 volts are wired in series,
|
|
| ** A centre grounded ( ie split 120v -0- 120v ) supply poses no problems
| either.
|
| Sometimes called a "balanced supply" and sold openly to the public.
|
| You are completely clueless.
Before I put a the label on you that many other people already have, I will
ask you to be specific. Let's see if you really understand this and can
actually read what has been posted ... by stating exactly what you think I
an clueless about. If you can't state this correctly, then what you are
doing is just making personal attacks (which most people will interpret as
someone who can't defend what they say in a technical way).
|> | The range of AC input voltage and frequency you mention is within the
|> | capability of most UPS on the market.
|>
|> But what about the ability to safely operate in all electrical systems in
|> the world
|
| ** Totally NEW question.
How is this a new question? You can't see the relation, and thus a basic
expansion of, the original question?
| (at the 200-240 volt configuration in countries like USA and Japan
|> that operate on 100-120 volts L-N with 2 opposiing phase lines which may
|> be
|> 180 degrees apart, or may be 120 degrees apart).
|
|
| ** A centre grounded ( ie split 120v -0- 120v ) supply poses no problems
| either.
|
| You are completely clueless.
Before I put a the label on you that many other people already have, I will
ask you to be specific. Let's see if you really understand this and can
actually read what has been posted ... by stating exactly what you think I
an clueless about. If you can't state this correctly, then what you are
doing is just making personal attacks (which most people will interpret as
someone who can't defend what they say in a technical way).
|> | Now, what is you actual question ??
|>
|> Same as before: "What would it take ...".
|
|
| ** Then yours is STILL an utterly silly question.
|
| For Christ's sake - TELL US what YOU think the safety problem is ??
The safety problems would depend on the specific design. If relays that can,
under conditions of failure (e.g. one of them might not make the switch for
reasons that might include an open coil) result in an unsafe condition (such
as exposing operators to dangerous voltage, or create a fault condition), then
it could be (should be) considered unsafe by listing agencies. That can be
mitigated by making the design use "double throw" relays that just cannot be
in both states at once (though could be in an in between state).
One design idea was to have 2 inverter sections in series, with each of the
3 connections having a relay that could connect that section to ground. But
this exposes at least two risks. One is relay operation failure could leave
the system ungrounded. Or if latching relays are involved, two could be
closed at once (due to an open operation failure) and a fault is created.
One way to mitigate that problem is for the control logic to always complete
the switching, AND test the continuity state, before activating inverter
operations. If supply power is lost, it could come back with different
grounding (for example, with Schuko, the plug can be inverted). Now for the
grounding of the derived system to be corrected to match, power output has to
be briefly shut off (even if for maybe only a cycle or two).
I've thought through quite a number of different design arrangements. Each
one has some issue somewhere. Many are issues that safety listing agencies
might have big concerns about.