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RE: This might be the one I want to turn into a project but is it 1/2 Amp? ping twystd

Posted by twystd (A) on July 21, 2017 at 00:30:56

In Reply to: This might be the one I want to turn into a project but is it 1/2 Amp? ping twystd posted by Ugly on July 20, 2017 at 18:40:16:

like others have stated, I believe it is almost certainly a 1/2 amp motor, my Papst motors draw ~ .25 amps at 120-123V (my usual line voltage range). All synchronous hysteresis motors are very inefficient, but lock onto frequency and have little to no cogging. I'm not familiar with that particular motor, but it is of interest to me. Even though it says it's a single phase motor, doesn't mean that it isn't a 3 phase wound motor, wired with a faking capacitor, to run on single phase.

If it is a three phase motor wired to run on single phase, running on true three phase makes them run even smoother, have much more torque (therefore more efficient), and they run cooler too. The 30 watt Papst motor has so much torque when run on 3 phase that it gets up to speed in no time at all.

There are many advantages of Pyramid's generator, they are: That the frequency is digitally generated and is much more accurate and steady compared to the frequency common to mains voltage. The power company measures the variation of frequency and averages over time to make your electric clocks run on time. You can tune the frequency to get an almost exact speed (accurate to about .0055 RPM on the platter). Once set the variation of frequency is so small as to be of little if any actual effect. IIRC it's .001% if my recall and math are correct that would be about .00003 (three one hundred thousandth) of an RPM on the platter. You can also change frequency to change speed, thereby not having to deal with mechanical linkages. Another really great advantage of Pyramids generator is that you can start it at high voltage, to get maximum torque at start up, and then automatically ramp down the voltage by as much as 1/2 (programmable), to maintain the speed. These motors when run at low voltage 3 phase, take any rumble from an already super smooth motor even lower, and have power to spare to run the platter.

The only reason to have a feedback loop and correction like the Phoenix Engineering Falcon and Road Runner would be for belt stretch, and motors like the Hurst motors. With an idler drive table, and a motor like the Papst, when run on three phase, I see little if any need for any feedback loop for speed variation, as you've pretty much eliminated those variables.

Looks to me like there are 4 leads, could be that it is a Y wound 3 phase motor, the Papst motors have 3 leads and are delta wound. The 1800 RPM is like the Papst motors. Looks like one of the very desirable Ashland motors ROK put on there transcription tables as well. I might be able to tell more by a schematic drawing of the external wiring. Very cool table, could benefit from a plinth upgrade. What does the platter weigh?

For those that may be interested, Pyramid's (Phoenix Engineer) SG4 generator, when used with his purpose built amplifier, and off the shelf DC motor, is a much more practical solution, especially for those that are running a TT with a Hurst motor. However, for those on the lunatic fringe like myself, a plinth upgrade, and a 3 phase VFD with that transcription motor, platter, and arm would be mighty inviting. After all this is the audio asylum. :-))

twystd

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