Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site sdcsvax.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!ihnp4!houxm!whuxl!whuxlm!akgua!sdcsvax!jc From: jc@sdcsvax.UUCP (John Cornelius) Newsgroups: net.micro Subject: Re: Voltage protection for micros Message-ID: <725@sdcsvax.UUCP> Date: Fri, 8-Mar-85 11:17:18 EST Article-I.D.: sdcsvax.725 Posted: Fri Mar 8 11:17:18 1985 Date-Received: Sun, 10-Mar-85 07:34:20 EST References: <8296@brl-tgr.UUCP> <6200044@hp-pcd.UUCP> Reply-To: jc@sdcsvax.UUCP (John Cornelius) Organization: EECS Dept. U.C. San Diego Lines: 36 Keywords: housepower voltage protection Summary: An inexpensive solution Well over 90% of the voltage abnormalities that will ruin your day (and your computer) are either over/under voltages of magnitude+- 50% or spikes/dropouts/noise lasting less than 20 milliseconds. IBM did a study about 7 years ago and concluded that the ability to ride through 2 cycles of peculiar power without the peculiarity reaching the machine would take care of about 90% of the power related maintenance calls. The general form of such protection is with isolation/regulation transformers. These fall into 3 types: Transformers that do one or the other Multitap isolation transformers that switch secondaries with SCRs Ferroresonant continuously regulating isolation transformers. My prejudices lie with the last of these because they are superior to switched designs in extreme cases of voltage abnormalities and those are the ones that make maintenance companies rich. The maintenance company that we use buys Isoreg transformers from us and installs them on micros that they are maintaining under contract. When the contract goes away, so does the Isoreg transformer. When the customer objects he sells it to the customer at 130% of his cost. He claims that these things get rid of virtually all of the undiagnosed intermittent problems. The Isoreg product goes for about $.50 per watt for 750VA and above and a little more for smaller units. They tend to run warm and the larger ones have fans for cooling. They are heavy and not particularly pretty but if you have irreplaceable data on your disk they are worth their weight in gold. Isoreg is in Littleton Massachusetts. Their phone number is (617)486-9483. John Cornelius Western Scientific