From owner-freebsd-questions@FreeBSD.ORG Tue Dec 2 02:39:09 2014 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id E2AFEB56 for ; Tue, 2 Dec 2014 02:39:08 +0000 (UTC) Received: from alogt.com (alogt.com [69.36.191.58]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id B72CAE60 for ; Tue, 2 Dec 2014 02:39:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=alogt.com; s=default; h=Content-Transfer-Encoding:Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Subject:Cc:To:From:Date; bh=Dto0e3qqpMJ4v3oxKYIDX1RhTr/E9MlPmce5GDo/wiQ=; b=WaDCuinbFKkWbRwRHKhaXrnueb52YBLfaq9SNXoEjtkPo1t/Ywm7d83sadyjUhH9zxRevuTnwGncvJANCR9UjthYq8VLGiiwzspmd9tOaqu1EL5a9b+sFFvC8PoXgVScKumKD7R1rLcEA++U25D6Sy4s2K5KP2hHG9XDxX0s2+0=; Received: from [114.121.160.169] (port=3138 helo=X220.alogt.com) by sl-508-2.slc.westdc.net with esmtpsa (TLSv1.2:AES128-GCM-SHA256:128) (Exim 4.84) (envelope-from ) id 1XvdMd-004533-6L; Mon, 01 Dec 2014 19:38:56 -0700 Date: Tue, 2 Dec 2014 10:38:47 +0800 From: Erich Dollansky To: Alejandro Imass Subject: Re: UPS for FreeBSD Message-ID: <20141202103847.564806a2@X220.alogt.com> In-Reply-To: References: <54777AB1.9010800@bluerosetech.com> <54779629.302@bluerosetech.com> <54789AF3.7090100@yahoo.com> <547AAC20.1050006@tridentusa.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - sl-508-2.slc.westdc.net X-AntiAbuse: Original Domain - freebsd.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - alogt.com X-Get-Message-Sender-Via: sl-508-2.slc.westdc.net: authenticated_id: erichsfreebsdlist@alogt.com X-Source: X-Source-Args: X-Source-Dir: Cc: John Johnstone , FreeBSD Questions 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: Tue, 02 Dec 2014 02:39:09 -0000 Hi, On Mon, 1 Dec 2014 12:39:24 -0500 Alejandro Imass wrote: > On Sun, Nov 30, 2014 at 12:33 AM, John Johnstone > wrote: > > Why do switching power supplies really care about the input wave > form? Most switching power supplies rectify with a full bridge and > capacitors and then switch from that rectified DC so why would it > care about the incoming waveform? So long as it's oscillating, > square, sine or triangular should work just the same. > the average volage over a square is much higher than over a sine. If the components are not designed for this, they will fail. You can see this effect by connecting a light bulb to an UPS and switch mains off an on again. The smaller the difference in brightness gets, the better the UPS emulates a sine. Of course, the life time of the light bulb gets reduced. > I think HF components would get filtered by design in the first few > stages of the switching PS so I don't understand why pure, or close > to pure sine wave is really important. What components are really at > risk from poor sine-wave inverter? Besides, UPS are designed to power > the equipment for a short period (either to shut-down or activate a > backup generator), so in reality there is that much more risk by > using a cheaper UPS? IS the price difference really worth it? > This is the question. Most power supplies will be able to handle the square waveform. Escpecially modern power supplies being able to handle any voltage from 100 to 250V. > Or is it all technical mumbo-jumbo to charge a lot more for "pure sine > wave", which honestly does NOT need sophisticated components like > someone said. It can be accomplished with a simple saw-tooth (with 2 > OP-Amps one as integrator and another one as comparator) and a > low-pass filter (a coil of wire). Inverter circuitry is really not > that complex and good sine-wave approximations are not that hard to > do. I am pretty sure a typical switching PS will do just fine if you > feed the square wave or an unfiltered saw-tooth sine wave into it. > It is the volume. When the cheaper UPSes appeared, their price advantage was pretty minor. I wonder meanwhile if it is not cheaper to use an inverter used in solar panel installations. At least for larger inverters, they have a clear price advantage but require batteries which are not available at the next corner shop. Erich