From owner-freebsd-questions@FreeBSD.ORG Mon Dec 1 17:39:31 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 E97EEE55 for ; Mon, 1 Dec 2014 17:39:30 +0000 (UTC) Received: from mail-qa0-f49.google.com (mail-qa0-f49.google.com [209.85.216.49]) (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 AEAEED8E for ; Mon, 1 Dec 2014 17:39:30 +0000 (UTC) Received: by mail-qa0-f49.google.com with SMTP id s7so7374459qap.8 for ; Mon, 01 Dec 2014 09:39:24 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=Ej2UUZsCt0d6e8e1p8MG0K1bkhLuVIZi5oJJxtpFvE4=; b=Y/1NHr1Ag1Kp8Lz6BrLJZHL4xAQVMj3yjYbRFMTGjHVUPvRm2MiXXbR+Dvcr+3ccRQ FnYiC/BIlosFDlQ5asZDUx3xsgWLLeNreWYX5mhVUIuuZZ1TdfoPrBH8nD2ArGraFLic /RIfHzEOGLbqw+kZqWlyFjR3FBinEJCzteRC5lgVZaxSlj8Ht/cEY3b9Hc5w6KjxC8fy vUAf47phkvL7SH6xXh8wbxGhs4QN2Ga1PuZZw2pekTlCjswpnurUr7QEctb8kLKKW2ST 6LBfzT0o4wxkRbfcQVIErj1PDTP/ZeimhSn/gq4DVHdPTg8ORYuvEA7JQSTHT42+vbPj ALlw== X-Gm-Message-State: ALoCoQkHKD/9EmTW5bfrLPOuYrg6qNb/fHZNO2h00gAGGs0rfmfN9OmpZ5ih2PHs6ED3te8CTEzu MIME-Version: 1.0 X-Received: by 10.224.38.5 with SMTP id z5mr88211992qad.89.1417455564234; Mon, 01 Dec 2014 09:39:24 -0800 (PST) Received: by 10.140.85.179 with HTTP; Mon, 1 Dec 2014 09:39:24 -0800 (PST) In-Reply-To: <547AAC20.1050006@tridentusa.com> References: <54777AB1.9010800@bluerosetech.com> <54779629.302@bluerosetech.com> <54789AF3.7090100@yahoo.com> <547AAC20.1050006@tridentusa.com> Date: Mon, 1 Dec 2014 12:39:24 -0500 Message-ID: Subject: Re: UPS for FreeBSD From: Alejandro Imass To: John Johnstone Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.18-1 Cc: 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: Mon, 01 Dec 2014 17:39:31 -0000 On Sun, Nov 30, 2014 at 12:33 AM, John Johnstone wrote: > I agree this thread is extremely long so I'll consolidate. > > > [...] > As far as "simulated" being a bad thing, by definition all UPS's have to > simulate a sine wave once the AC power goes away. It is just a question of > how close an approximation is it. There's no question that a 60 Hz square > wave would be a poor approximation. > > 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. 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? 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. Anyway just MHO. Best, Alejandro Imass