From: Bob Blick <bobblick@outlook.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
Sender: "piclist-bounces@mit.edu" <piclist-bounces@mit.edu>
Date: Tue, 26 Jan 2021 10:34:00 -0800
Subject: Re: [EE] Connecting european device to US main.
Thread-Topic: [EE] Connecting european device to US main.
Thread-Index: AQHW8/RmXZqKiodJ90+0CG2FBE+dHqo6D9aAgAAiNYCAAAZVmg==
Message-ID:
 <BYAPR02MB4055BB93100B483AAAF36371DCBC9@BYAPR02MB4055.namprd02.prod.outlook.com>
References:
 <CADX+YscZLisg30CYMMNNU=TXGCEUpLj+H9uY-QSNW8MVR-sxYA@mail.gmail.com>
	<7cc8c501-9e58-1d50-de8d-0e6ca40243cd@p10link.net>,
	<e227495284a07c6472e2041116f86013.squirrel@mai.hallikainen.org>
In-Reply-To: <e227495284a07c6472e2041116f86013.squirrel@mai.hallikainen.org>
Reply-To: Microcontroller discussion list - Public. <piclist@mit.edu>
Accept-Language: en-US
Content-Language: en-US
X-MS-Exchange-Organization-SenderIdResult: Pass
X-MS-Exchange-Organization-PRD: mit.edu
X-MS-TNEF-Correlator:
acceptlanguage: en-US
received-spf: Pass (protection.outlook.com: domain of outlook.com designates
	40.92.18.64 as permitted sender) receiver=protection.outlook.com;
	client-ip=40.92.18.64;	helo=NAM11-CO1-obe.outbound.protection.outlook.com; 
dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=outlook.com;
	s=selector1;
	h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck;
	bh=V0NeR/WjWlB5vV4CagkdmDd/JR3VBZp8giAGwGPjOF8=;
	b=gE1GBSXTvzIu3KFfv9XbLh/8Q33F4yPsYxL68FDeAEptT0eHFsc/vbILc5vvOADPjfAOi6+Vq6N5bInBV+6k9fso6lWgMy4QiCoRc3dKaycrstspTHZkxWS2VJbXYKkfTuZl6KxMqCgZUrMqTrGGvdN1tDRiuihnDl4soUmN81WIRbspMygnlMvJePXlAzgVL5BMHLo/Jo+EPqBgf57Ye70I4rPSoomnHZ4+mY1rlfDluRN/nhHovwssRK4X6NmdO8Gkct52NAwb0RphG8WVpD6eSFi7zgeWB2PT85OwRkYieyvvV5XTEx59t+Iyuj4zlzAr/0X68IpHDu0OAcqvpg==
authentication-results: spf=pass (sender IP is 40.92.18.64)
	smtp.mailfrom=outlook.com; mit.edu; dkim=pass (signature was verified)
	header.d=outlook.com; mit.edu;	dmarc=pass action=none
 header.from=outlook.com; 
errors-to: piclist-bounces@mit.edu
list-id: "Microcontroller discussion list - Public." <piclist.mit.edu>
list-post: <mailto:piclist@mit.edu>
x-beenthere: piclist@mit.edu
x-mailman-version: 2.1.6
x-topics: [EE]
x-mime-autoconverted: from quoted-printable to 8bit by PCH.mit.edu id
	10QIYIUx032299
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0

Hi Harold,

If you look at a residential North American breaker panel, you'll see lots =
of single circuit breakers for 120V circuits, and some wide 240V breakers t=
hat grab both busbars. The 240V breakers disconnect both phases even if onl=
y one phase causes the trip. It's a code requirement.

Drawing a 240V load from two opposite-phased 120V breakers is not allowed b=
ecause of the safety concerns, even if it does work.

On the other hand, running two 120V branches from a 240V breaker seems safe=
.. I don't know if it's allowed by code, probably not, it could make diagnos=
ing trips more difficult.

Friendly regards, Bob

________________________________________
From: piclist-bounces@mit.edu <piclist-bounces@mit.edu> on behalf of Harold=
 Hallikainen=20
Sent: Tuesday, January 26, 2021 9:59 AM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Connecting european device to US main.

I agree that phase to phase will give 240 V (unless you're on a 3 phase
wye, in which case it will be 208 V). Most electronic devices now have
"universal" power supplies that work from something like 100 V to 260 V.

One thought on doing a phase to phase connection is the loss of
overcurrent protection. I think pretty much everything only fuses the hot
side of the power line. That guarantees no high voltage in a device that
blows a fuse (blowing a fuse in the neutral would remove an overcurrent
load but leave line voltage in the device). But, if operating phase to
phase, what about a "neutral" to ground short? There would be no
overcurrent protection at the device (just the branch circuit protection).

I have thought of powering audio equipment that has a universal power
supply from 240 V phase to phase to provide it with "balanced power" that
results in a cancellation of ground leakage current due to the EMI filter
Y capacitors. But, I am concerned about a lack of protection  on one side
of the line.

Harold

--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.