On Mon, 29 Feb 2016 05:38:39 +0000 (UTC), you wrote:
>Stefan Trethan:
>
>I don't know how often the members of this group will encounter the type of industrial transformers that
>you describe. But I do know that isolation (not insulation) is a factor to be considered,,,,,,,,,often when
>connecting your test equipment up to equipment that you might be troubleshooting, designing, etc.
>
>Refer to the conventional three-phase configuration that most of us encounter.
In the US, Line, neutral, line is not three phase, it's more two phase
since the two lines are 180 degrees out of phase with each other, thus
adding (120-0-120) give 240.
True three phase power is three lines, each 120 degrees apart. You'll
find it in aircraft and industrial plants. It can be wired with a
common (wye) or with an implied center (delta). It does require
special transformers, and the voltages are not always what you expect.
You'll frequently find military surplus/aviation equipment with true 3
phase power, and it's annoying to convert ∗IF∗ it will even run on
60/50 Hz. Some test equipment is rated to run from 50/60 to 400 Hz,
but that was generally an option.
BTW: the whine you might hear when boarding a commercial aircraft
frequently comes from the 400 Hz power, not the engines (although that
can be there, too).
Harvey
>
>Regards,
>
>Roland F. Harriston, P.D.
>
>----- Original Message -----
>
>From: "Stefan Trethan stefan_trethan@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
>To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
>Sent: Sunday, February 28, 2016 10:14:10 PM
>Subject: Re: [Homebrew_PCBs] Re: drill pcb
>
>
>
>Strictly speaking there are differences between an industrial control
>transformer and an isolation transformer.
>The isolation is often stronger with a dedicated isolation
>transformer, sometimes the windings are even physically separated in
>different chambers or on different shanks, instead of on top of each
>other.
>As a result coupling capacitance is lower with an isolation
>transformer, but also magnetic coupling is worse.
>
>So in some situations you may require an actual isolation transformer.
>
>Many high quality control transformers fulfill the minimum
>requirements for a safety isolation transformer, but always check the
>datasheet.
>
>ST
>
>On Thu, Feb 25, 2016 at 5:15 PM, Brad Thompson
>brad.thompson@... [Homebrew_PCBs]
><Homebrew_PCBs@yahoogroups.com> wrote:
>> If you need to power a 120VAC item from a 240 VAC
>> line (or vice versa), you can use
>> a transformer ∗∗with isolated windings∗∗ designed exactly for this
>> purpose. These are sometimes referred to as
>> "industrial control transformers".
>>
>> 73--
>>
>> Brad AA1IP
>>
>>
>