WALT@MAINE.BITNET (Walter G. Horbert) (09/12/87)
The following equipment is available 10/10/87:
(1) IBM 3033-U16 Processor Complex
Features: 16 MB main storage
12 I/O channels (2 byte mux, 10 block)
57 nanosecond cycle time
5 million instructions/sec
(1) IBM 3037 Power & Cooling Distribution Unit
(1) IBM 3036 Console
Price for all items is $5,000 plus freight.
Not available separately. Contact:
Walter G. Horbert (Walt@Maine.Bitnet)
Operations Manager
University of Maine System
Computing And Data Processing Services
Orono, Maine 04469kai@uicsrd.csrd.uiuc.edu (09/19/87)
> Richard Morin ({hoptoad,ptsfa}!cfcl!rdm) writes: > > I made a firm decision a few years ago which has served me well ever > since: Never buy equipment that won't run in an unconditioned room > on standard wall current. Sounds like you don't use anything larger than a workstation, maybe a small Microvax. Nowhere near the power of a 3033. This offer (if it is valid) sounds a lot like the Commodore 128 story. Buy the cpu for next to nothing, followed by lots of little extras, like software, peripherals, networking equipment, not to mention the staff of at least ten it takes to run a large IBM data center (systems and operations) effectively. And a 3033 IS LARGE too. I wonder who pays shipping? I'll bet the US Government would be interested. Having worked for them in the past, I can vouch for the fact they they LIKE using old IBM systems. The place I worked at spent more than the cost of a new faster, cooler, smaller 4341 getting an old 370/165 to work with MVS and support more than the IBM recommended maximum 3 Mb memory. Patrick Wolfe Internet: pwolfe@kai.com UUCP: ...!{uunet,ihnp4}!uiucuxc!kailand!pwolfe The opinions expressed here are my own, NOT my employers.
davy@ea.ecn.purdue.edu (Dave Curry) (09/20/87)
In article <46300008@uicsrd> kai@uicsrd.csrd.uiuc.edu writes: > >> Richard Morin ({hoptoad,ptsfa}!cfcl!rdm) writes: >> >> I made a firm decision a few years ago which has served me well ever >> since: Never buy equipment that won't run in an unconditioned room >> on standard wall current. > >Sounds like you don't use anything larger than a workstation, maybe a >small Microvax. Nowhere near the power of a 3033. > Well, you could use some other slightly larger machines too... even an IBM. The IBM 9370 runs in an unconditioned environment, and will crank along at about 6 MIPS. It's actually a pretty slick box - now if only it ran UNIX! Sun-3's and Sun-4's and stuff don't need A/C either. The mainframe in question (IBM 3033) is probably not worth even the $5,000 UNLESS you already have one and want spares. The maintenance cost on one, according to our local IBM salesman, is about $14,000 per month. They recently pulled one out of the Admin. DP Center... they used a BOLT CUTTER to dismantle it, and trashed it. --Dave Curry
rjd@tiger.UUCP (09/21/87)
> > I made a firm decision a few years ago which has served me well ever > > since: Never buy equipment that won't run in an unconditioned room > > on standard wall current. > > Sounds like you don't use anything larger than a workstation, maybe a > small Microvax. Nowhere near the power of a 3033. Nooo, an AT&T 3B2 model 600 is VERY powerful and runs off house current in an unconditioned room. For that matter, the model 500 is almost as powerful (less disk storage and memory space) and will also. What do you determine as "powerful"? Supporting around or just under 100 users is powerful to me (especially for a desktop, or under-desk mini...) Randy Davis
djl@mips.UUCP (Dan Levin) (09/22/87)
In article <46300008@uicsrd>, kai@uicsrd.csrd.uiuc.edu writes: > > > Richard Morin ({hoptoad,ptsfa}!cfcl!rdm) writes: > > > > I made a firm decision a few years ago which has served me well ever > > since: Never buy equipment that won't run in an unconditioned room > > on standard wall current. > > Sounds like you don't use anything larger than a workstation, maybe a > small Microvax. Nowhere near the power of a 3033. Hummm, I am sitting in a room with three machines, each plugged into a wall socket (standard 110v 15 amp). The room is pleasantly cool, but is conditioned exactly the same as the rest of the office space. The floor is carpeted. The machines in this room have a total of 24 Mg. of memory (8 Mg. each, they are small ones), ~1 Gig of disk space, and combined CPU power of 15 VAX 11/780's. I call that larger than a "small Microvax". There is another office in this building with 4 such R2000 based machines in it, totaling 23 MIPS, over 70 Mg. of memory, and over 3 Gig of disk. It is a bit warm, but it also has 4 people and a big window facing South. Welcome to the late 1980's... -- ***dan {decwrl,pyramid,ames}!mips!djl djl@mips.com (No, Really! Trust Me.)
res@ihlpe.ATT.COM (Rich Strebendt @ AT&T-C/IS (IW); formerly) (09/25/87)
In article <140200009@tiger.UUCP>, rjd@tiger.UUCP writes: > > > > I made a firm decision a few years ago which has served me well ever > > > since: Never buy equipment that won't run in an unconditioned room > > > on standard wall current. > > > > Sounds like you don't use anything larger than a workstation, maybe a > > small Microvax. Nowhere near the power of a 3033. > > Nooo, an AT&T 3B2 model 600 is VERY powerful and runs off house > current in an unconditioned room. Similarly, the AT&T 3B4000 Computer, growable to >40MIPs capacity (using the usual Marketing type MIPs :-) has the same sort of environmental requirements as the 3B2 does. It does not need a raised floor (we just had one on display on a quarry tile floor) and will keep running at temperatures human beings consider uncomfortable (I am not sure off the top of my head what the advertised specs are). It runs off 110vac, though it needs a bit more current than a table lamp (and can be had in 250vac 50Hz versions for customers outside the USA). Rich Strebendt ...!ihnp4![iwsl6|ihaxa|ihlpe]!res
crayops@uxc.cso.uiuc.edu (09/27/87)
Written 12:58 am Sep 16, 1987 by rdm@cfcl.UUCP (Richard Morin) >I made a firm decision a few years ago which has served me well ever >since: Never buy equipment that won't run in an unconditioned room >on standard wall current. Well then, you won't be getting a Cray soon, will you? Maybe the Cray-4 will fit your needs, but by then, it'll be a laptop anyway. Could I be biased? Naaaaaaah. >Richard Morin, proprietor {hoptoad,ptsfa}!cfcl!rdm >Canta Forda Computer Laboratory +1 415 994 6860 ^^^^^^^^^^^ Oh, I get it. Try to get a grant, maybe then you Canna Forda comp. lab. . Crayops This is the opinion of one of the crayops but not them all.
ccplumb@watmath.UUCP (09/29/87)
In article <177200006@uxc.cso.uiuc.edu> crayops@uxc.cso.uiuc.edu writes: >Written 12:58 am Sep 16, 1987 by rdm@cfcl.UUCP (Richard Morin) >>I made a firm decision a few years ago which has served me well ever >>since: Never buy equipment that won't run in an unconditioned room >>on standard wall current. > >Well then, you won't be getting a Cray soon, will you? Maybe the >Cray-4 will fit your needs, but by then, it'll be a laptop anyway. > >Could I be biased? Naaaaaaah. For those of us making do with VAXen and things, what does a cray require? I know it has its own heavy-duty cooling (that bench-thing around it), so it should be able to cope with a reasonable temperature range, and it would seem odd if it didn't take reasonably standard voltages - even if you need to run a new feeder cable in to supply the hundreds of amps a cray draws. So, except for the fact that "wall current" usually passes through a 15 or 20-amp fuse on its way to the computer, why doesn't a cray fit this description? Just curious. -- -Colin Plumb (watmath!ccplumb) .. I think I'll KILL myself by leaping out of this 14th STOREY WINDOW while reading ERICA JONG'S poetry!!
heisterb@uxe.cso.uiuc.edu.UUCP (10/01/87)
[ diet Coke - Just for the chemistry of it! ] A CRAY is like an iceberg, what you see is a small part of what there really is. First power supply. Something like a gizillion amps of 3 phase 220 (or is it 400V?). This runs a motor generator that produces 400Hz 3 phase (don't know the voltage, it's not in my book) that goes to the main power controller. You never see the motor generator, it's usually hidden in a basement. There's separate power controllers for the mainframe, the ios, and the ssd. The bench around the mainframe and other parts has additional power regulators for each section (12 for the mainframe). So it doesn't just plug into a wall. I'm guessing that the power consumption of an X-MP/48, IOS, and 128MW SSD is about 500-700kVA. As for cooling, the above system uses two 25 ton condensers. The main- frame et. al. is cooled by freon running through copper or aluminum tubing, with heat exchange from freon to water in the condensers. Then of course there's the chillers on the roof for the water. It costs an unbelievable amount to run a CRAY. It's an entirely different class of environmental support than most mainframes. But it's worth it! The above information from "down the street" and the "CRAY X-MP Four-Processor Mainframe Reference Manual" with the cute orange cover sheet! DJ Heisterberg National Center for Supercomputing Applications heisterb@uxe.cso.uiuc.edu 13004@ncsa[a|b].ncsa.uiuc.edu
woolsey@nsc.UUCP (10/02/87)
In article <14944@watmath.waterloo.edu> ccplumb@watmath.waterloo.edu (Colin Plumb) writes: >For those of us making do with VAXen and things, what does a cray >require? I know it has its own heavy-duty cooling (that bench-thing >around it), No, those are power supplies, one for each column. Each power supply puts out something on the order of 300 Amps. >so it should be able to cope with a reasonable temperature >range, and it would seem odd if it didn't take reasonably standard >voltages - even if you need to run a new feeder cable in to supply the >hundreds of amps a cray draws. > >So, except for the fact that "wall current" usually passes through a 15 >or 20-amp fuse on its way to the computer, why doesn't a cray fit this >description? Cray power is 400Hz, for one thing. This means a motor-generator, and you usually don't want those things where anyone can hear them, which means a separate room for them. Crays come with a large power/temperature monitoring and control box, about the size of two refrigerators. It's supposed to shut the machine down if the temperature in any column goes outside preset limits, something like 82? degrees. One of these temperature sensors failed on SN12 before we (my former employer) got the machine, and it almost melted the solder on the boards as the temperature rose. Cray cooling uses water or freon (I forget which) pumped through the aluminum columns. This fluid then goes through a fairly large heat exchanger. A better name for it is cooling towers. These things are fairly massive as well, and the one I dealt with went next to the MG building. Not to mention that Cray CPU's are heavy. They consist of eight or twelve aluminum columns containing 144 boards each. Each board pair shares a copper plate. The power supplies aren't massless, either. We had to reinforce the raised floor where the machine was going to be. When they wheeled it in they used fairly thick rigid metal plates to spread the weight over that portion of the floor between the door and the CPU location. There's rather a lot of plumbing running under the floor between the CPU and the cooling towers, too. All of the above site preparation took a couple of months, I think. SN12 has since been retired. Its gutted hull sits in the lobby of the Minnesota Supercomputer Center. The above applies only to Cray-1s and Cray X/MPs. Cray-2s are a different aquarium. -- LERMINATING PREVIOUS SESSION. PQEASE RETRY. Jeff Woolsey National Semiconductor Corporation ...!nsc!woolsey -or- woolsey@nsc.COM -or- woolsey@umn-cs.ARPA
bldrnr@apple.UUCP (10/02/87)
In article <4673@nsc.nsc.com> woolsey@nsc.UUCP (Jeff Woolsey) writes: >In article <14944@watmath.waterloo.edu> ccplumb@watmath.waterloo.edu (Colin Plumb) writes: >Cray power is 400Hz, for one thing. This means a motor-generator, and >you usually don't want those things where anyone can hear them, which >means a separate room for them. Cray power, if I remeber correctly is motor-generated for isolation reasons rather than any need for transmission. As it turns out a Cray needs on the order of 15KW source. This can only be supplied by a main feed of some kind from a power company main. Which is 400hz 3-phase(?). >Cray cooling uses water or freon (I forget which) pumped through the >aluminum columns. This fluid then goes through a fairly large heat >exchanger. Freon. One interesting note on the cooling system for Apple's XM-P: It is whisper quiet. The Cupertino neigborhood next to the building that houses the Cray is about 50 yards from the 'containment building' the most incredible aspect of this is that from outside you would never know that there was a 12 ton throughbred roaring away in side. 1 meter of high density acoustic insulator did the trick. All the way around the back room where the freon pumps and water heat exchanger were...including the MASSIVE doors to the outside world. When I got a tour of the machine I found out why the computer was so well isolated from tender ears... The only thing I have to compare the sound of 4(6?) motor-gen to is jet engines at *close* range. It might have been the acoustics of the room, but GEEZ that stuff is loud! --/--bldrnr--> @apple.UUCP
roy@phri.UUCP (10/02/87)
In article <4673@nsc.nsc.com> woolsey@nsc.UUCP (Jeff Woolsey) writes: > Cray power is 400Hz Ah, so that's why they run so fast! :-) But seriously, I'm curious; why? The only other place I know where 400 Hz power is used is on aircraft, because you can make the power transformer cores lighter. -- Roy Smith, {allegra,cmcl2,philabs}!phri!roy System Administrator, Public Health Research Institute 455 First Avenue, New York, NY 10016
jaym@nuchat.UUCP (Jay Maynard) (10/04/87)
In article <2944@phri.UUCP>, roy@phri.UUCP (Roy Smith) writes: > But seriously, I'm curious; why? The only other place I know where > 400 Hz power is used is on aircraft, because you can make the power > transformer cores lighter. Exactly. Have you considered just *how much* a Cray (or a big-series IBM [all of the water-cooled systems use 416 {not 400!...$^%$#} Hz power]) would weigh if they used 60 Hz power instead? Not to mention the hum from the massive transformer cores vibrating at 60 Hz, and the energy loss... -- Jay Maynard, K5ZC (@WB5BBW)...>splut!< | temporarily at uunet!nuchat!jaym Never ascribe to malice that which can | while splut is down (@#*(&$% ST4051!!) adequately be explained by stupidity. | GEnie: JAYMAYNARD CI$: 71036,1603 The opinions herein are shared by neither of my cats, much less anyone else.
roy@phri.UUCP (Roy Smith) (10/05/87)
In article <365@nuchat.UUCP> jaym@nuchat.UUCP (Jay Maynard) writes: > Have you considered just *how much* a Cray [...] would weigh if they > used 60 Hz power instead? Not to mention the hum from the massive > transformer cores vibrating at 60 Hz, and the energy loss... Still doesn't make sense. Surely the weight you get to save in the cores is more than offset by the M-G set you need to turn 60 Hz into 400 (or, as Jay says, 416) Hz. Ditto for the noise and energy loss. There is nothing inherently wrong with big 60 Hz transformers; just walk out to your nearest power substation and take a look. Aircraft use 400 Hz because saving weight is one of the most important aspects of aircraft design. They generate their own power, so it's also no big deal to use a non-standard line frequency; they don't have to interface to the power grid. There must be something more than just weight savings involved in the decision to use 400 Hz in a Cray. For Earth-bound machines, weight is just not that important; you can always make the floor stronger. -- Roy Smith, {allegra,cmcl2,philabs}!phri!roy System Administrator, Public Health Research Institute 455 First Avenue, New York, NY 10016
vanhove@XN.LL.MIT.EDU (Patrick Van Hove) (10/06/87)
My 0.02 cents: Maybe the deal with 416 hz is energy storage. In any power supply, you need <BIG> capacitors to start removing the ripple after AC-DC conversion. The capacitors may be a lot smaller at higher frequency. Basically, you are trading electrostatic or chemical storage of energy in the capacitors for mechanical storage in the flywheel of your 60hz/416hz converter. Patrick ... just kidding, I know less about power supplies than about greek mythology, to say the least, and my employer certainly didn't hire me for either.
larry@kitty.UUCP (Larry Lippman) (10/06/87)
In article <2952@phri.UUCP>, roy@phri.UUCP (Roy Smith) writes: > > Have you considered just *how much* a Cray [...] would weigh if they > > used 60 Hz power instead? Not to mention the hum from the massive > > transformer cores vibrating at 60 Hz, and the energy loss... > > Still doesn't make sense. Surely the weight you get to save in the > cores is more than offset by the M-G set you need to turn 60 Hz into 400 > (or, as Jay says, 416) Hz. Ditto for the noise and energy loss. There is > nothing inherently wrong with big 60 Hz transformers; just walk out to your > nearest power substation and take a look. > Aircraft use 400 Hz because saving weight is one of the most > important aspects of aircraft design. They generate their own power, so > it's also no big deal to use a non-standard line frequency; they don't have > to interface to the power grid. There must be something more than just > weight savings involved in the decision to use 400 Hz in a Cray. For > Earth-bound machines, weight is just not that important; you can always > make the floor stronger. I too, am puzzled as to why Cray would use an M-G set and 400 Hz power supplies. With the advent of quality switching power supplies in the past several years, and the use of other hybrid power supply designs which use DC-DC converters, large AC transformers as used in purely linear power supplies are becoming a thing of the past. There is a ready supply :-) of off-the-shelf OEM transformers and power supplies intended for military applications that operate at 400 Hz. These devices are, in some cases, an order of magnitude smaller than a 60 Hz counterpart (especially when they use toroidal transformers). Perhaps Cray uses an extensive "distributed" power supply concept, and thereby desires many small power supplies which are located close to their loads. Since solid-state 60->400 Hz inverters are readily available and more efficient than M-G sets (such inverters have great application in aircraft ground support), I am puzzled why an M-G set would be used. However, I can think of one good reason: the M-G set may have an associated flywheel which provides some immunity from AC power-line disturbances. There could also be a tandem motor that is supplied from batteries to achieve a true UPS capability. This is, of course, pure speculation on my part. I have never even seen a Cray "in the flesh". I do wish, however, that someone in the know solves the mystery! <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {hplabs|ihnp4|mtune|seismo|utzoo}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today
bldrnr@apple.UUCP (Brian Hurley) (10/06/87)
In article <2952@phri.UUCP> roy@phri.UUCP (Roy Smith) writes: >(or, as Jay says, 416) Hz. Ditto for the noise and energy loss. There is >nothing inherently wrong with big 60 Hz transformers; just walk out to your >nearest power substation and take a look. This is not quite true. The reason for a Cray using 400/416 Hz power has to do with the source more than weight considerations. The amout of power used is very large (I don't know the figures off hand, but it may fall into the hundreds of KW) the olny source for this kind of power is a Sub-station feed. Which is NOT 60Hz. If you transmitted even 100KW of power @ 440VAC that would result in a curennt flow of approx 318 AMPS! Copper ain't that cheap! If I remeber my basic transmission line math, the higher the AC frequency, the smaller the transmission line needs to be, but I don't remeber the math that would show a direct corralation. The end results of high frequency AC power include lighter equipment as well as lower cost and lower loss transmission. There are disadvantages to this type of power as well, the equipment for regulating 440VAC @ 400Hz is not as inexpensive as 60Hz, but imagine the transformer that could handle 100KW @110VAC, 60Hz... > Aircraft use 400 Hz because saving weight is one of the most >important aspects of aircraft design. They generate their own power, so >it's also no big deal to use a non-standard line frequency; they don't have >to interface to the power grid. There must be something more than just >weight savings involved in the decision to use 400 Hz in a Cray. For >Earth-bound machines, weight is just not that important; you can always >make the floor stronger. > - Roy Smith Again the weight is not the issue. The solution to the interface is simple. Design a motor that works on 400Hz and have it drive a 60Hz Generator. If the design is mechanicly sound, the losses are comparable to a transformer of comparable size. -Brian ----------------------------------------------------------------------------- / --/--bldrnr--> Apple Computer Inc. 10500 N. De Anza Blvd, Cupertino, CA. \ \ Disclaimer: No warranties are expressed or implied PERIOD! / / Whatever I say, >>I SAY<< keep my employer out of it! \ \ / / UUCP: bldrnr@apple.UUCP CSNET: bldrnr@apple.CSNET \ \ ARPA: bldrnr@apple.apple.COM voice @ 408/973-6679 / -----------------------------------------------------------------------------
msf@amelia (Michael S. Fischbein) (10/07/87)
In article <2952@phri.UUCP> roy@phri.UUCP (Roy Smith) writes: >In article <365@nuchat.UUCP> jaym@nuchat.UUCP (Jay Maynard) writes: >> Have you considered just *how much* a Cray [...] would weigh if they >> used 60 Hz power instead? Not to mention the hum from the massive >> transformer cores vibrating at 60 Hz, and the energy loss... > > Still doesn't make sense. Surely the weight you get to save in the >cores is more than offset by the M-G set you need to turn 60 Hz into 400 etc. Not only aircraft, but much shipboard equipment uses 400Hz. The goal is certainly not saving weight. In most case, the answer is fairly simple: Most electronic equipment, especially digital stuff does not run on AC at 60Hz, 400Hz or any other sine wave; it runs on DC. Now, how do you convert AC to DC? (Basically) A full wave rectifier and a capacitor to fill in the ripple. How big does the capacitor have to be? Depends on the frequency of the incoming AC. Higher freq, smaller cap. Look at your computer's power supply sometime; bet more space is taken up by capacitors than any other component (not counting heat sinks; that's not electronics but mechanics). Take a look at some of the big iron power supplies; they have some truly monster caps in some machines. So that's wye we delta the freqency (bad pun, sorry): make the conversion to DC more efficient. Check out switching power supplies in an electronics text. mike Michael Fischbein msf@prandtl.nas.nasa.gov ...!seismo!decuac!csmunix!icase!msf These are my opinions and not necessarily official views of any organization.
larry@kitty.UUCP (Larry Lippman) (10/07/87)
In article <6424@apple.UUCP>, bldrnr@apple.UUCP (Brian Hurley) writes: > >(or, as Jay says, 416) Hz. Ditto for the noise and energy loss. There is > >nothing inherently wrong with big 60 Hz transformers; just walk out to your > >nearest power substation and take a look. > > This is not quite true. The reason for a Cray using 400/416 Hz power > has to do with the source more than weight considerations. The amout > of power used is very large (I don't know the figures off hand, but it may > fall into the hundreds of KW) the olny source for this kind of power > is a Sub-station feed. Which is NOT 60Hz. I'm not certain what you mean by a "Sub-station feed", but utility companies can deliver some megawatts of power to a customer site without having to resort to voltages above 480 volts AC within the customer site. As an example, a 1200 ampere 480/277 volt wye service will deliver about one megawatt. 480 volt "busbar" service is available to 3,000 amperes or more (a couple of megawatts, minimum). If you are implying that incoming utility company service at high power is NOT 60 Hz, this is incorrect. > If you transmitted even 100KW of > power @ 440VAC that would result in a curennt flow of approx 318 AMPS! You really need to figure 480 volts, since 440 delta or grounded delta service is almost non-existant; on the other hand, I'll give you some reactive KVA allowance - we'll say a power factor of .95. So, the I = 100,000 / (1.732 * 480 * .95) = 127 amperes > Copper ain't that cheap! If I remeber my basic transmission line math, the > higher the AC frequency, the smaller the transmission line needs to be, > but I don't remeber the math that would show a direct corralation. The > end results of high frequency AC power include lighter equipment as well as > lower cost and lower loss transmission. What you have is skin effect, which means you can use hollow conductors, but not conductors of smaller diameter. From a practical standpoint, there is no advantage in power transmission based upon using 400 vs 60 Hz in the relatively short-distance environment of a computer system. > There are disadvantages to this type > of power as well, the equipment for regulating 440VAC @ 400Hz is not as > inexpensive as 60Hz, but imagine the transformer that could handle 100KW > @110VAC, 60Hz... I'm not certain how large you think this transformer would be, but I have seen 100 kva transformers used in electroplating power supplies that measure about 22 inches on a side, are about 42 inches high, and weigh about 600 pounds. In a computer application, however, I don't believe any designer in their right mind would NOT use distributed power supplies, with each supply being no greater than a couple of kva in capacity. > Again the weight is not the issue. The solution to the interface is simple. > Design a motor that works on 400Hz and have it drive a 60Hz Generator. If > the design is mechanicly sound, the losses are comparable to a transformer > of comparable size. Transformers, especially those of toroidal design, can achieve efficiencies of 98% or more. Ain't no way that any rotating component power converter can match that efficiency! As a point of information, even HUGE transformers, like those used in utility substations are more efficient than you may think. As an example, I have seen a 5 megawatt three-phase transformer at an industrial plant down the road converting 34.5 kV delta to 4.16 kV delta that has a maximum loss of 5% (i.e., 95% efficiency). I read the nameplate; WHY I got close enough the read the nameplate is another story... <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {hplabs|ihnp4|mtune|seismo|utzoo}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"
darrelj@sdcrdcf.UUCP (Darrel VanBuer) (10/07/87)
In article <6424@apple.UUCP> bldrnr@apple.UUCP (Brian Hurley) writes: >In article <2952@phri.UUCP> roy@phri.UUCP (Roy Smith) writes: >>(or, as Jay says, 416) Hz. Ditto for the noise and energy loss. There is >>nothing inherently wrong with big 60 Hz transformers; just walk out to your >>nearest power substation and take a look. > >fall into the hundreds of KW) the olny source for this kind of power >is a Sub-station feed. Which is NOT 60Hz. If you transmitted even 100KW of >power @ 440VAC that would result in a curennt flow of approx 318 AMPS! >Copper ain't that cheap! If I remeber my basic transmission line math, the >higher the AC frequency, the smaller the transmission line needs to be, > -Brian >/ UUCP: bldrnr@apple.UUCP CSNET: bldrnr@apple.CSNET \ >\ ARPA: bldrnr@apple.apple.COM voice @ 408/973-6679 / I'm going to stay away from the trade off between MG set to 400 Hz and smaller power supplies vs direct conversion to low voltage, but I suspect there are significant advantages either way which come down to a judgement call by a Cray engineer. Almost all of the nationwide power grid does run on 60 Hz, only voltage is varied in most cases. Power is a function of voltage times current, and is nearly independent of frequency. Generally, higher voltages are used for carrying large amounts of power long distances (and as voltage goes up, so does tower height). Some highlines run at over a million volts). DC is actually superior for long distance transmission, but until relatively recently, there was no efficent and reliable way to convert between ultra high voltage DC and 60 Hz AC compatible with the majority of the power grid. The original choice of AC for the grid was because of the easy transformation of voltages. -- Darrel J. Van Buer, PhD; unisys; 2525 Colorado Ave; Santa Monica, CA 90406 (213)829-7511 x5449 KI6VY darrel@CAM.UNISYS.COM or ...{allegra,burdvax,cbosgd,hplabs,ihnp4,sdcsvax}!sdcrdcf!darrelj
roy@phri.UUCP (Roy Smith) (10/07/87)
In article <6424@apple.UUCP> bldrnr@apple.UUCP (Brian Hurley) writes: > The reason for a Cray using 400/416 Hz power has to do with the source > more than weight considerations. The amout of power used is very large > ([...] it may fall into the hundreds of KW) the only source for this kind > of power is a Sub-station feed. Which is NOT 60Hz. If you transmitted > even 100KW of power @ 440VAC that would result in a curennt flow of > approx 318 AMPS! Hogwash. Except for a very very few (experimental?) DC links, and some telemetry-over-power, *everything* on The Grid is 60Hz. Also, for an industrial site, a few hundred kW is just not that much. Our building, for example, (a moderate size light-industrial building in Manhattan) has two 6000 Amp, 120-Volt, 3-phase feeders. The feeders are not so much wires as copper bus bars running maybe 50 feet to a transformer under the street, which I believe steps down from the 13.8 kV sub-distribution. I suspect that 13.8 kV (if not higher) is available in just about any industrial park in the country. > Design a motor that works on 400Hz and have it drive a 60Hz Generator. > If the design is mechanicly sound, the losses are comparable to a > transformer of comparable size. This is true. Good power transformers and good M-G sets both have efficiencies on the order of 95%. Not particularly germaine, but true. I suspect there may be some confusion going on. It is common to find 3-phase, 240 Volt wiring in industrial plants. The 240 Volt reading is in Y configuration -- each phase to neutral. In a Delta configuration (i.e. looking at the phase-to-phase voltage) you get 417 or 416 Volts (depending on how you like to round off). Cables and panel boxes with 416 in them tend to be prominently marked with stickers reading "240/416" to distinguish them from the more common 120/208. Could it be that somebody saw one of these stickers and thought the "416" referred to the frequency instead of the Delta voltage? Somebody suggested the the M-G sets are there for electrical isolation, to provide mechanical inertia to ride over line transients, and to provide a simple hookup for an alternate power source (put a diesel on the same shaft as the M-G set, for example). All of these are reasonable explanations; saving weight in the transforer cores is not, at least not by itself. -- Roy Smith, {allegra,cmcl2,philabs}!phri!roy System Administrator, Public Health Research Institute 455 First Avenue, New York, NY 10016
larry@kitty.UUCP (Larry Lippman) (10/07/87)
[I am trying to move this discussion to sci.electronics, where at this point it really belongs.] In article <3011@ames.arpa>, msf@amelia (Michael S. Fischbein) writes: > Not only aircraft, but much shipboard equipment uses 400Hz. The goal is > certainly not saving weight. In most case, the answer is fairly simple: > > Most electronic equipment, especially digital stuff does not run on AC > at 60Hz, 400Hz or any other sine wave; it runs on DC. Now, how do you > convert AC to DC? (Basically) A full wave rectifier and a capacitor to > fill in the ripple. How big does the capacitor have to be? Depends on the > frequency of the incoming AC. Higher freq, smaller cap. Look at your > computer's power supply sometime; bet more space is taken up by capacitors > than any other component (not counting heat sinks; that's not electronics > but mechanics). Take a look at some of the big iron power supplies; > they have some truly monster caps in some machines. Space is generally not a problem on shipboard electronic equipment, nor is weight, so 400 Hz power is used on some shipboard apparatus for neither of these two reasons. The reason 400 Hz is used on some shipboard equipment is to accommodate the needs of navigation, fire control and antenna positioning systems which use gyros and servomechanisms. The majority of military gyro motors, servo motors, resolvers, synchros, control transformers (the synchro variety), other types of magnetic angle position encoders, etc. operates from 400 Hz power. The reason for this is that 400 Hz results in smaller packages, better resolution, and faster response than does a 60 Hz counterpart for a servomechanism or gyro application. While there are shipboard fire control and antenna positioning (as in radar) systems which use 60 Hz for servomechanisms, today it is more common to see 400 Hz being used. <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {hplabs|ihnp4|mtune|seismo|utzoo}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"
farren@gethen.UUCP (Michael J. Farren) (10/07/87)
In article <3011@ames.arpa> msf@amelia.UUCP (Michael S. Fischbein) writes: > >Not only aircraft, but much shipboard equipment uses 400Hz. The goal is >certainly not saving weight. In most case, the answer is fairly simple: Maybe that's why Cray uses 400 Hz - he could only afford surplus mil-spec power supplies in the prototype :-) Seriously, there are a number of good reasons to use 400 Hz. If, as I suspect, the Crays use a number of individual power supplies, those supplies can be made considerably smaller than when using 60 Hz, because of previously mentioned considerations of transformer design and capacitance requirements. There may well be other considerations beyond these; I would be very interested in hearing from someone who knows what some of those considerations are - maybe someone associated with Cray? Speak up, man! -- ---------------- Michael J. Farren "... if the church put in half the time on covetousness unisoft!gethen!farren that it does on lust, this would be a better world ..." gethen!farren@lll-winken.arpa Garrison Keillor, "Lake Wobegon Days"
sampson@killer.UUCP (Steve Sampson) (10/08/87)
I may have missed someone mentioning this, but 400 Hz may have been selected to allow it to work with aircraft and ship generators. I can think of many aircraft in the inventory that could use the computing power (military).
esf00@amdahl.amdahl.com (Elliott S. Frank) (10/08/87)
In article <2075@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: > > I too, am puzzled as to why Cray would use an M-G set and 400 Hz >power supplies. [...] Since solid-state 60->400 Hz inverters are readily >available and more efficient than M-G sets (such inverters have great >application in aircraft ground support), I am puzzled why an M-G set >would be used. It's up to the customer's Computer Center (or Facilities Department, or Purchasing Department). The Cray machine (like an Amdahl 5890) requires 415 Hz power (yes, three phase). How the customer elects to provide that power is up to him. Computer Decisions magazine is full of ads from vendors providing all sorts of systems that supply the right amount of 415Hz 3-phase power for Amdahls, Crays, CDC's, and IBM's. -- Elliott Frank ...!{hplabs,ames,sun}!amdahl!esf00 (408) 746-6384 or ....!{bnrmtv,drivax,hoptoad}!amdahl!esf00 [the above opinions are strictly mine, if anyone's.] [the above signature may or may not be repeated, depending upon some inscrutable property of the mailer-of-the-week.]
pf@diab.UUCP (Per Fogelstrom) (10/12/87)
In article <2075@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: >In article <2952@phri.UUCP>, roy@phri.UUCP (Roy Smith) writes: >> > Have you considered just *how much* a Cray [...] would weigh if they >> > used 60 Hz power instead? Not to mention the hum from the massive >> > transformer cores vibrating at 60 Hz, and the energy loss... >> > There is a ready supply :-) of off-the-shelf OEM transformers and >power supplies intended for military applications that operate at 400 Hz. ========================^^^^^^^^^^^^^^^^^^^^^^^^^^====================== Mabye You hit the head of the nail !!!..........
ems@apple.UUCP (Mike Smith) (10/19/87)
In article <2075@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: > > I too, am puzzled as to why Cray would use an M-G set and 400 Hz >power supplies. [...] Since solid-state 60->400 Hz inverters are readily >available and more efficient than M-G sets (such inverters have great >application in aircraft ground support), I am puzzled why an M-G set >would be used. MG sets have inertia. This is usually enough to coast through minor power dropouts (<1/2 cycle...) and provide *SIGNIFICANT* power filtering for spike protection ... The effeciency of MG sets can also be quite high, but that is usually not a factor in the decision. Reliability, power filtering, ruggedness (They can really take a punch!) are usually most important. -- E. Michael Smith ...!sun!apple!ems 'If you can dream it, you can do it' Walt Disney This is the obligatory disclaimer of everything. (Including but not limited to: typos, spelling, diction, logic, and nuclear war)