From owner-freebsd-questions@FreeBSD.ORG Sun Nov 30 21:03:12 2014 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 93CC83B9 for ; Sun, 30 Nov 2014 21:03:12 +0000 (UTC) Received: from mail-wi0-x235.google.com (mail-wi0-x235.google.com [IPv6:2a00:1450:400c:c05::235]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 1E249335 for ; Sun, 30 Nov 2014 21:03:12 +0000 (UTC) Received: by mail-wi0-f181.google.com with SMTP id r20so15467020wiv.14 for ; Sun, 30 Nov 2014 13:03:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=20120113; h=date:from:to:subject:message-id:in-reply-to:references:mime-version :content-type:content-transfer-encoding; bh=bAmkA66lGoLH7b3vTzk1HTjBYhZUINAS46Rk8XaG0/M=; b=izcOrMVChUl8ww6joISSilkknJS7XcZTky2ayOMAGPZzTM/rucSyySnLUoAVSNEQdY rqAzBaWUfGeh/AQ76j1z9D9Yo6LMJeVCeeLkJzoC+oe+L2r+xq93EpyLhhbIbWhiTixu skFaxLo1CIk25B3uctZzFAfWIV/AVe4vehc+v+t7yJcUE4s6AJLSWVfqoF9CS0cZufNM FjbjAZbhP7l45F2htalRE3vMf9actf1zH9ZYOumFoNLlgjTXYpzNtYZy23yUkjV98GcP yd6HhXyGFHoW/IEpSNEb15LIlXAO569eQZ3P2ATBiFU+P9H28wswcKdFwAkWkmZBgpu1 0Ryw== X-Received: by 10.180.107.1 with SMTP id gy1mr77853432wib.8.1417381390519; Sun, 30 Nov 2014 13:03:10 -0800 (PST) Received: from gumby.homeunix.com (bcdc819a.skybroadband.com. [188.220.129.154]) by mx.google.com with ESMTPSA id dc8sm25639807wib.7.2014.11.30.13.03.08 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 30 Nov 2014 13:03:10 -0800 (PST) Date: Sun, 30 Nov 2014 21:03:05 +0000 From: RW To: freebsd-questions@freebsd.org Subject: Re: OT: UPS for FreeBSD Message-ID: <20141130210305.2d62bbb1@gumby.homeunix.com> In-Reply-To: <547B7093.1020305@bluerosetech.com> References: <54777AB1.9010800@bluerosetech.com> <54779629.302@bluerosetech.com> <5478BD4F.7020306@yahoo.com> <5478BEE6.30308@bluerosetech.com> <5478CC08.9090307@yahoo.com> <20141128204722.561f948e@archlinux> <5478F16A.80605@yahoo.com> <54791d3a.w/pI0kak03d+3nKC%perryh@pluto.rain.com> <20141129113405.3d1bd1d6@X220.alogt.com> <54798883.saa13h6lE6rPwZCf%perryh@pluto.rain.com> <20141129113018.17759e2a@archlinux> <547a52e9.tCBMi6xWobou5Fcd%perryh@pluto.rain.com> <547B7093.1020305@bluerosetech.com> X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.22; amd64-portbld-freebsd10.0) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 30 Nov 2014 21:03:12 -0000 On Sun, 30 Nov 2014 11:31:31 -0800 Darren Pilgrim wrote: > On 11/29/2014 3:12 PM, Perry Hutchison wrote: > > Presuming a reasonable amount of capacitance on the output, > > a half wave (single diode) rectifier should produce a DC > > output roughly equal to the peak value of the AC input, > > which is indeed ~1.4 * the RMS AC voltage. A two-diode > > full-wave rectifier using a center tap will also produce DC > > of ~1.4 * the RMS voltage of the entire winding (and with > > the advantage of less ripple). > > > > However, a full wave bridge (4 diodes) should produce a DC > > output roughly equal to the peak-to-peak value of the AC > > input, or ~2.8 * the RMS voltage. > > An unloaded, ideal, single-phase FWR produces Vdc = 0.900Vrms. The > factor is 2sqrt(2)/pi, to be precise. A half-wave rectifier produces > half that. That's the mean voltage, which is of limited relevance. > From where did you get your figures? He's referring to a rectifier charging a smoothing capacitor; the voltage will rise to sqrt(2)*Vrms. He's added on an unnecessary factor of two - possibly because he's mixing it up with a bridge-rectifier in a centre-tap configuration.