Re: [time-nuts] The home time-lab
Or the current version:
Large AC motor driving a LARGE flywheel with an AC (and/or -48VDC) generator on the other side feeding a very large battery plant. If mains drops more than 1/2 cycle it connects the turbine and starts it up.
We had a 5MW one at $OLD_GIG for feeding our supercomputer factory.
It was rumored that at least one customer location kept one of their turbines (redundant) idling at all times because they could not afford to loose a data set.
On Jul 25, 2016, at 09:55, Bob Camp kb8tq@n1k.org wrote:
Hi
If you go back far enough in time …. there is another alternative:
Big rectifier bank, turning AC into DC, often off of multiple phases or sources.
Big DC motor running into a fairly large flywheel.
AC generator (or in some cases DC generators) running off of the shaft
A tuning fork (yes state of the art timing) based control on the AC output frequency
A saturated reactor control loop on the generator side, same thing on the motor side.
Wonderfull stuff. State of the art UPS for your shipboard computer in 1962. Ear muffs anyone?
Bob
On Jul 25, 2016, at 8:39 AM, Charles Steinmetz csteinmetz@yandex.com wrote:
Chris wrote:
I've never thought UPS were a good idea for anything but a computer
that needs to shut down gracefully. For your use you need something
that cleans up the AC mains power.
A proper "online" (or "double conversion") UPS does just that. It always provides cleanly-generated sine-wave power from a DC-AC converter. Most will even deliver crystal-controlled power (i.e., non-synchronous with the AC line) in several frequency increments, if you desire, as well as a choice of regulated output voltages. (For obvious reasons, they are usually operated synchronously.)
They are much more effective than ferroresonant supplies at removing glitches from the mains supply.
You must be referring to "offline" backup supplies.
Best regards,
Charles
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The reason they call it a modified sine wave is that it is a square
wave with the same peak and RMS voltages as a sine wave. Since the
RMS value of a (bipolar) square wave is equal to its peak value, it
has to include parts at zero or a lower voltage. Some inverters use
additional voltage steps to more closely approximate a sine wave but I
think they are less common now that true sine outputs have become more
economical.
I do not know why Don Lancaster's Magic Sinewave idea is not used more
widely. Does it have patent issues? Maybe it is not economical
compared to a true sine output.
In the past I have used the predicable sine average responding and RMS
values of a square wave to calibrate its peak-to-peak value for use as
a calibration source. This is useful for calibrating analog
oscilloscopes if you have an uncalibrated source but a good sine
average responding or RMS (or both for a sanity check) AC voltmeter.
On Mon, 25 Jul 2016 10:29:02 -0700, you wrote:
Hi Chris:
The APC RS1500 uses what they call modified sine wave, but I call modified square wave, i.e. it's a square wave with a
couple of parts that are at zero volts.
Don Lancaster promoted "Magic Sinewaves" where a pulse modulated waveform drives an H-bridge. The leading and trailing
edges are determined using the idea of FFT so that all the harmonics up to some number (typically 9 to thirty something)
are zero. There were also 3-phase versions. But he no longer sells any hardware.
PS I'm looking for a source of 3-phase 400 Hz 115 VAC to power a North Finding Gryo.
http://www.prc68.com/I/WildARK2.html
On Mon, 25 Jul 2016 12:28:52 -0500
David davidwhess@gmail.com wrote:
I have never seen one which did not use a class-D output with L-C
filtering. Total efficiency is in the 84 to 92 percent range.
Actually, the better ones have 3 level or 5 level inverters (or even more).
Ie their output stages can not only produce +340V and -340V, but
also 0V (for the 3 level) and +/-170V (for the 5 level). For obvious
reasons, this gives a nicer output waveform that needs less filtering.
While the 3 level is easy to build, the 5 levels and more require
a flying capacitor (or multiple for more than 5 levels). The handling of
this capacitor is kind of tricky as you need to ensure that the flying
capacitor has the right voltage under all conditions. For those interested,
quite a few papers on that topic are publicly available. Please excuse me
not linking to any of these, but I know very little of inverters, so I do
not know which one of the papers would be the right ones to read.
Attila Kinali
--
Malek's Law:
Any simple idea will be worded in the most complicated way.
On 7/25/16 6:55 AM, Bob Camp wrote:
Hi
If you go back far enough in time …. there is another alternative:
Big rectifier bank, turning AC into DC, often off of multiple phases or sources.
Big DC motor running into a fairly large flywheel.
AC generator (or in some cases DC generators) running off of the shaft
A tuning fork (yes state of the art timing) based control on the AC output frequency
A saturated reactor control loop on the generator side, same thing on the motor side.
Wonderfull stuff. State of the art UPS for your shipboard computer in 1962. Ear muffs anyone?
Bob
we had a system like this to turn 60 Hz into 50 Hz with a toothed belt
drive between synchronous motor and synchronous generator. It whined..
"Satan's Siren" is what we called it.
IBM mainframes used a similar scheme but I can't remember the details.
On Jul 26, 2016, at 12:04 AM, jimlux jimlux@earthlink.net wrote:
IBM mainframes used a similar scheme but I can't remember the details.
Yes. We had 3 3090 https://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP3090.html’s and they all incorporated multiple motor/generator units ( 3089 ) to generate 400Hz power ( in addition to chilled water distribution modules, etc. )
IBM 3089 Power Unit
The IBM 3089 is connected to your mainline supply. It is designed to provide a stabilized 400 Hertz AC power source to units of the Processor Complex