Very clever motor design 8 pole armature/stator Basically infinite pole field/rotor Smooth AC motor approaching DC FREQ = 33.333 / 120 x 8 = 2.222 Hz
Yea, basic design goes back to the original Dual CS 701 with the EDS-1000 coreless 8-pole motor in 1973, many of the subsequent coreless direct drive motors were derived from that one, some a bit too closely and they ran into patent problems. The new Technics motors are actually 9-pole designs, as shown in the illustrations in post above.
Thanks Never said I could count The bad part? I counted 1/2 dozen times, kept losing the starting point Makes f = 2.50000 Hz
It's kind of blurred, lol You have 9 armature/stator coils But the field/rotor magnet is continuous But for it to rotate the AC must rotate around the coils. most motors are concentric, this is planar Not sure what to call them other than poles. I'd like to see how the coils are wired.
Doesn't change how a motor works. Between each coil is a slot. Poles are magnetic - we can count those via attraction, or if we knew the drive frequency and phases we can calculate them.
These are coreless, slotless motors we are talking about here. The poles are magnetic domains formed within the magnet structure, kind of like shown in illustration below, which would be like the SL-1200G motor with the twin rotors sandwiching the windings ... Technics says it is a 9-pole motor, and Dual said the EDS-1000 was a 8-pole motor, that's how you know, but you can also guess by the number of stator windings. The Dual EDS-1000 motor has two offset layers of 8 bifilar windings, as shown in picture below ...
After looking at the manual, more confused They describe it as a brushless DC motor Then give a waveform for the drive V? This has 3 coils, looks like 3 phase? https://www.deepsonic.ch/deep/docs_manuals/technics_sl-1200mk2_sl-1210mk2_service_manual_b.pdf this shows it better, a hybrid of sorts AC on a DC bias, A1, A2, A3, DC = 11 V, AC = 4 V At least for these http://www.revolution.pt/pdfs/sl1210mkii.pdf
FWIW: When it comes to motors, the nomenclature of AC and DC is sometimes a bit misleading. Many DC servos for example are actually AC but run on DC because of built in circuitry that converts it to AC.
Yes all fairly academic. However you said the 'illustrations shown in the post above' show that it's 9 pole, while the illustrations didn't show magnetic poles but 9 coils, which is why I asked how do you know it's 9 poles? Also note that Technic's state the 10R motor is 12 poles and 18 coils. I understand it's slotless but for the purposes of motor geometry whether coils or slots it's the same thing with this design.
Brushless DC motor is a loose term. They are actually synchronous AC motors. DC voltage is not applied directly to the motor, but rather to the controller which generates AC voltage applied to the coils of the synchronous motor. The resulting magnetic field interacts with the permanent magnet of the rotor. The rotor always rotates at the same speed as the applied magnetic field, which makes it 'synchronous'. They always have a rotor position feedback (usually an encoder) , and it also acts as a speed feedback. Typically they are capable of not only precise speed, but also precise positioning. Not needed in a TT obviously. That is generic knowledge. I don't know all nuances of Technics motor design, but it looks like that's what it is.
Here is the waveform DC biased AC at least for this model That likely makes it smoother, most power provided by DC, AC provides the rotating field. Some synchronous motors had a DC generator on the shaft that supplied the rotor/field I thru slip rings. motors? THE text http://prof.usb.ve/jaller/Fitzgerald.pdf
Yep But I don't see synchronous motors too often anymore. And I see x,000 HP all the time. Some had a DC power supply.
I see them every day at work . Servo motors for CNC machines and automation. Exclusively synchronous AC motors these days. Prime AC supply converted to DC. DC converted to AC again to feed those motors. Fantastic devices. Can maintain nominal torque even at standstill unlike DC garbage 2-3 decades ago.
So this elevated discussion b/w all you brainiacs is very impressive. ..And I truly mean that. ..I wish I could follow along. But the question that really needs to be answered is: which of these technologies is distinguishable from the other?? ..What is the outcome data? I don't doubt that the GA/E measures better than at GR. ..Or that a 1000R measure better than a GA/E. ..But can a person who is unable to see the turntable able to distinguish one from the other?
Assuming you have the same tonearms & cartridges* I don't think many can hear the difference from GAE/G to the 1000R in a blind A-B test. Phono stage, cartridge and arm/cartridge setup have a bigger sonic impact on what we hear from the turntable itself. *Two same cartridges is not easy to have, they are made by hand and have tolerances. To manage the same exact setup in two arms is also not an easy job. Everything a man makes is not perfect, the turntable is last centurys invention and by it's nature far from perfect. It's a needle on a non flat surface that's affected from everything around it.
Yes, basically everything man made has a tolerance. You could conclude that because of tolerances no comparison can ever be made between any object, if you want to change only one variable... but that would result a slippery slope fallacy: Because if tolerances always have that big of an impact, it means measurement equipment is too inaccurate as well and we should doubt anything mankind has ever measured and all the knowledge based on that empirical evidence. It’s all about significance, not just when it comes to tolerances, but also when it comes to differences in performance.
So, no one has an idea if this patent is used in the G/GR/MK7? US8729887B2 - Rotation angle sensor - Google Patents