lørdag den 2. oktober 2021 kl. 23.20.18 UTC+2 skrev snipped-for-privacy@gmail.com:
VFDs are great for motors but they don't work for everything, and you need some way to store energy for the valleys of the AC waveform, inertia of the Rotary Phase Converter helps with that
No, I have a Corgi.
I said he's a dumb bass. That's a fish.
By which John Doe means that Politifact is rude about his preferred sort of nonsense.
His childish enthusiasm for the idea that there is some kind of "Deep State" is exactly the kind of nonsense that sensible people jeer at, which doesn't make him happy either. What might make him happy could be a course on how to think straight, but it's not obvious that he's got enough intelligence to take advantage of such a course, and even if it worked he'd end up painfully embarrassed by the stuff he has been posting.
The John Doe troll stated the following in message-id <sdhn7c$pkp$ snipped-for-privacy@dont-email.me:
And the John Doe troll stated the following in message-id <sg3kr7$qt5$ snipped-for-privacy@dont-email.me:
And yet, the clueless John Doe troll has itself posted yet another incorrectly formatted USENET posting on Sat, 2 Oct 2021 20:50:19 -0000 (UTC) in message-id <sjagmb$eu2$ snipped-for-privacy@dont-email.me.
The John Doe troll stated the following in message-id <sdhn7c$pkp$ snipped-for-privacy@dont-email.me:
And the John Doe troll stated the following in message-id <sg3kr7$qt5$ snipped-for-privacy@dont-email.me:
And yet, the clueless John Doe troll has itself posted yet another incorrectly formatted USENET posting on Sat, 2 Oct 2021 21:01:32 -0000 (UTC) in message-id <sjahbb$eu2$ snipped-for-privacy@dont-email.me.
On a sunny day (Sat, 2 Oct 2021 14:20:14 -0700 (PDT)) it happened Michael Terrell snipped-for-privacy@gmail.com wrote in snipped-for-privacy@googlegroups.com:
In the sixties that was used to provide 3 phase power to perfotape (audio) recorders to synchonize those with the film projectors, used to do voice-over of movies etc. There waa a special room where motor and generator was located (sound proof sort of) From full stop to 25 fps.. or so.
Well, yeah, but a simple three-phase motor (with optional flywheel) does the energy storage and smooths the waveform well, so the RPC virtues are available in VFD systems, as long as your idler motor-flywheel doesn't misbehave (vibrate hard at resonances, for instance).
That's he beauty of a VFD, you can easily change the frequency, by just turning a pot.
Cool. Show us.
Good grief, Amazon sells electronic phase converters, starting below $100. That's a business I don't want to be in.
Some of the VFD do not even put out anything remotely resembling a stepped sine wave. Where I worked we had some that you could hear the motors sing with a high pitched sound. No where near the normal 10 to
200 Hz or so that one might think. The waveform was sort of like a pulse width modulation. I have no idea what it actually was but we used them on motors from around 1 HP or less to over 300 HP motors.One thing that you have to be careful about lowering the speed of the motors is if they are depenind on the air flow developed by the motor fan for cooling. If they are you have to use some other trickery than just reducing the frequency like some of the VFDs do.
Most of our FVDs were controled by a milliamp output of a PLC or other computer device. Feed the VFD a 4 to 20 ma signal to go from a low speed to the maximum speed. A few had either knobs or a digital display for the percentage of speed.
søndag den 3. oktober 2021 kl. 20.30.24 UTC+2 skrev Ralph Mowery:
They all use PWM to generate the sinewave-ish output matching what the motor needs. Some of the older ones make a high pitched noise, they ran the PMW at a rather low frequency because the was what the technology was up to
clearly not the ones that could run on single phase input
most VFDs need to be substially derated when run on single phase compared to three-phase because they don't have enough capacitance on the DC rail and the rectifier can't handle the current
snipped-for-privacy@fonz.dk wrote: =================
** Clearly not the giant 300HP jobs mentioned by Ralph either.BTW
Learn how to trim and do not post with ZERO breaks between the previous words.
And begin a sentence with a damn capital.
...... Phil
That's why I mentioned both. There is also a third, more expensive converter. A variable frequency oscillator, followed by a high power, low frequency amplifier with a step up transformer. These come in single or three phase. The choice depends on the load.
The John Doe troll stated the following in message-id <sdhn7c$pkp$ snipped-for-privacy@dont-email.me:
And the John Doe troll stated the following in message-id <sg3kr7$qt5$ snipped-for-privacy@dont-email.me:
And yet, the clueless John Doe troll has itself posted yet another incorrectly formatted USENET posting on Tue, 5 Oct 2021 14:43:58 -0000 (UTC) in message-id <sjhobe$d5f$ snipped-for-privacy@dont-email.me.
John Larkin wrote: ===============
** A partial explanation of WHY the fake set was created for Biden is here:...... Phil
That's a bit silly. All presentations are prepared - at least to some extent. The teleprompter makes it easier to read your notes, hides the fact that this is what you are doing and save you from the work of memorising formulations that fit the situation without up-setting anybody.
In this situation the president is his own ventriloquist - what he says is always going to owe quite a bit to his staff, but president's had speechwriters long before there were any teleprompters.
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