From owner-freebsd-questions@FreeBSD.ORG Tue Dec 2 11:23:04 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 C29E6496 for ; Tue, 2 Dec 2014 11:23:04 +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 981FFAC7 for ; Tue, 2 Dec 2014 11:23:04 +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=PajihTidhkeIe/+soczK7SC57xui2kZMcHTi8iKEUv4=; b=H/XVPWFkRJgY5NzeOL6PmODWnVwWv3Zn6bOvWQuXIsHKvi6gcsgZlo5ukH4CrVuSkq0YF4kUUOAem13/rtKg10SMm6PJSJp1A0wzAE6ozdpE1F4kcBHrIoFKTTMgTjpJnMiuUQJtyhtFbnCjwsirlx0rCVLViTp0BNw60bJfTtc=; Received: from [114.124.4.186] (port=50989 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 1XvlXo-002XV3-FC; Tue, 02 Dec 2014 04:23:02 -0700 Date: Tue, 2 Dec 2014 19:22:52 +0800 From: Erich Dollansky To: Alejandro Imass Subject: Re: UPS for FreeBSD Message-ID: <20141202192252.7cab41b5@X220.alogt.com> In-Reply-To: References: <54777AB1.9010800@bluerosetech.com> <54779629.302@bluerosetech.com> <54789AF3.7090100@yahoo.com> <547AAC20.1050006@tridentusa.com> <20141202103847.564806a2@X220.alogt.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 11:23:04 -0000 Hi, On Mon, 1 Dec 2014 22:46:58 -0500 Alejandro Imass wrote: > On Mon, Dec 1, 2014 at 9:38 PM, Erich Dollansky > > wrote: > > > On Mon, 1 Dec 2014 12:39:24 -0500 > > Alejandro Imass wrote: > > > > > On Sun, Nov 30, 2014 at 12:33 AM, John Johnstone > > > wrote: > > > > > 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. > > > > > Should not be a problem for any modern switching power supply. In > fact the higher the RMS the more efficient it will operate. The RMS > of the sine x/SQRT(2) of a square wave is just x, where x is the peak > to peak voltage. The peak to peak of 120V is around 170V which is > just fine for most switching power supplies which are rated for about > 250V RMS. It _could_ be a bit of a problem is the UPS is for 240V but > I have never personally seen one in a North American store. Besides > any 240V UPS manufacturer would have to know this and honestly I > don't really think that any UPS uses a square wave. > the world is a bit bigger than the USA. > I will be sure to test this with an oscilloscope when I finally buy > the UPS that started this thread - I promise I will buy the cheapest > one I find and post pictures of the output waveform ;-) > There are sites which do this already. I just do not have URLs at hand. They normally do not do a simple squere but use i.e. 3 squares. The higher the price gets, the smaller the squares will get. > [...] > > > > 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. > > > > > Actually I was referring to another comment that suggested that HF > harmonics from saw-tooth emulation or square wave "ring" could somehow > affect the switching PS of a typical computer. I think this is > unlikely because it will get filtered by the first rectification > circuitry of the switching power supply (I am no expert and could be > wrong and maybe some switching PS would be sensitive to this, but I > really doubt it). HF does affect some transformers and linear > equipment and still is very unlikely. > Yes, it should be like this. > [..] > > > > 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. > > > > The problem I think is the switch-over speed. It would be really cool > to find UPS that use *any* external battery, and you could just use a > car battery for example which is very reliable, durable and readily > available. > Oh, I did this once for a client at a very remote location. He only has had a lousy generator but wanted to run a normal PC in a decent manner without spending too much money. We took the a cheap car battery charger, two car batteries and an off-shelve inverter to be used in a truck. Nothing can beat this as the UPS is always on. So no switch over. The clear disadvantage are the batteries. Car batteries are designed for a high load for a short period of time. The result with a low load over a longer period of time is bad. The best I have seen yet are batteries used for solar panels. The quality of the batteries is really outstanding. The price is even more outstanding. Erich