[Boatanchors] Running European 230 VAC on our AC

[Sheldon Daitch]

Robert,

You are correct in what I found with the autotransformer
for the stove.

I obviously wasn't clear in what I wrote.

Sheldon

On 10/21/2012 6:32 PM, WA5CAB at cs.com wrote:
> Glen,
>
> What he said was that what should have been the neutral connection for the
> autotransformer (the I/O common) was connected to Line, not Neutral.  Which
> put what should have been the Neutral connection for the internals at Line
> (120 RMS) instead of near ground.
>
> Robert
>
> In a message dated 10/21/2012 10:08:25 AM Central Daylight Time,
> gzook at yahoo.com writes:
>> The neutral is NOT 120 VAC above ground!  That assumes that one side of
>> the 240 VAC is grounded which is not the case in this country.  The
>> secondary on the "pole pig" (distribution transformer) is center tapped with 120
>> VAC on either side of the center tap.  The connection to this center tap is
>> the neutral.
>>
>> At the entrance to the building, the connection to the neutral is grounded
>> by an external connection usually to a ground rod driven near the entrance
>> point.  This puts the neutral basically at "ground" potential.  In
>> 240-volt 3-wire systems (no longer approved for new installations) all 3-wires
>> coming from the pole pig continue to the load.  In 240-volt 4-wire systems
>> there is an additional "ground wire" which is connected to the point at which
>> the neutral connects to the external ground rod.
>>
>> For the 120 VAC distributed within the building, one side of the 240 VAC
>> and the neutral are involved which gives 120 VAC.  Then, a ground wire is
>> added for safety.
>>   
>> Glen, K9STH
>>
>>
>> Website:  http://k9sth.com
>>
>>
>> ________________________________
>> From: Sheldon Daitch <sdaitch at kuw.ibb.gov>
>> To:
>> Cc: "boatanchors at mailman.qth.net" <boatanchors at mailman.qth.net>
>> Sent: Sunday, October 21, 2012 5:06 AM
>> Subject: Re: [Boatanchors] Running European 230 VAC on our AC
>>
>> As noted, some 240VAC US appliances do need the neutral
>> to pick up the 120VAC for some 120VAC applications in the
>> unit.
>>
>> We have a US built stove which the manufacturer has to add a
>> stepdown transformer for the export model, since the 230VAC
>> systems outside the US typically do not have the neutral
>> centertap.
>>
>> In our stove, that stepdown transformer was an autotransfomer,
>> not an isolation transformer and it failed.  I discovered that the
>> way the transformer was wired and the stove was wired into
>> our 230VAC system that the common of the autotransformer
>> was wired to the high leg of the wiring and perhaps that was
>> the cause of the eventual failure of the transformer.
>>
>> I bring this up, as running  230VAC equipment which is designed
>> for a hot and neutral might have some problems if the neutral
>> leg is actually 120VAC above ground.  In theory, no, but with
>> polarized systems, the powered unit is normally going to see
>> near-ground voltage outside the US, but in the US, the neutral
>> leg would be 120VAC above ground.
>>
>> (One interesting aspect of many 230VAC systems outside the
>> US is that many residential systems are three phase, and
>> with 230VAC phase to neutral, phase to phase voltages are
>> in the 400VAC range.)
>>
> Robert & Susan Downs - Houston
> wa5cab dot com (Web Store)
> MVPA 9480
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