Turntable Synchronous Motor AC Speed Control Driver (PSU) in Current Drive Mode ?

tiefbassuebertr · 2020-08-16 12:59 am

tiefbassuebertr · 2021-01-04 3:31 pm

no information concerning current drive mode for turntable synchronous motor control units ?

Pyramid · 2021-01-04 4:17 pm

What is it you are trying to accomplish? Lower distortion of the drive signal? What benefit do you perceive by doing so? According to Mark Kelly, a slight amount of anti-phase 3rd harmonic distortion is actually beneficial.

Ugly · 2021-01-04 5:55 pm

Pyramid said:
According to Mark Kelly, a slight amount of anti-phase 3rd harmonic distortion is actually beneficial.

Is this 3rd harmonic "tuning" intended to compensate for to nonlinearity in the source, the load, or both?

tiefbassuebertr · 2021-01-04 6:02 pm

Pyramid said:
What is it you are trying to accomplish? Lower distortion of the drive signal? What benefit do you perceive by doing so? According to Mark Kelly, a slight amount of anti-phase 3rd harmonic distortion is actually beneficial.

Getting best possible sound quality at a power supply/motor control for Linn LP12 record player and similar models with same drive motor (as an alternative for Valhalla/Lingo).
If I knew what benefit I am perceive, I would not ask here (this is the intention to start this thread).
Check out
Linn Lingo vs. Dr. Fuß or Square-Wave vs. Sine Wave Oscillator for Motor Control
Maybe the isolation transformer between control circuit output and motor input from the Dr. Fuß power supply provide additional H3.
Maybe this transformer also create more current control character.

If I were able to make exact measurements of voltage, motor current flow and 1KHz spectrum with a test record like to find under
Linn LP Playing System Measurements | Stereophile.com
I could find out everything on my own.

Pyramid · 2021-01-04 11:14 pm

Ugly said:
Is this 3rd harmonic "tuning" intended to compensate for to nonlinearity in the source, the load, or both?

A small amount of H3 was thought to reduce cogging in AC synch motors.

Ugly · 2021-01-05 5:18 pm

Pyramid said:
A small amount of H3 was thought to reduce cogging in AC synch motors.

Interesting. Apparently everyone does this but I'm just now finding out. Fancy! Example:(PDF) Torque Ripple Reduction of Interior Permanent Magnet Synchronous Motor Using Harmonic Injected Current

tiefbassuebertr · 2021-01-07 4:49 pm

Thank you. Is this PDF under
https://www.koreascience.or.kr/article/JAKO200934939515685.pdf
also available in Englisch ?

diyrayk · 2021-01-08 12:22 am

This PDF is available here, and should be in English:

Torque Ripple Reduction of Interior Permanent Magnet Synchronous Motor Using Harmonic Injected Current
Torque Ripple Reduction of Interior Permanent Magnet Synchronous Motor Using Harmonic Injected Current - IEEE Journals & Magazine

It's not free, it is $15 for IEEE members and $33 for non-members. Click on the red "PDF" button then click on the "Purchase" tab.

Ray K

diyrayk · 2021-01-08 3:22 am

Pyramid said:
..... According to Mark Kelly, a slight amount of anti-phase 3rd harmonic distortion is actually beneficial.

I think Mark is on the right track. I’m an electrical engineer and before I retired I worked on projects with multi-thousand horsepower 3-phase synchronous motors. In this size range the rotors are built with wound coil poles and energized with DC current instead of using rotating permanent magnets. The rotor pole pieces are contoured and the stationary coils which are connected to 3-phase AC are overlapped so that the rotating magnetic field and the “pull” from each phase is as purely sinusoidal as possible. Because the 3 phases are 120 electrical degrees apart, the mechanical torque developed by each of the three phases ideally sums to a uniform cog-free torque on the shaft. If it’s not done right then you get vibration, and it puts harmonic distortion on the incoming AC power line.

It appears to me that “shaping” the magnetic field in small synchronous motors is physically difficult but pre-distorting the AC input voltage with engineered “anti-harmonics’’ to compensate for the inherent cogging would be effective, and that is what the research paper demonstrates. I have a feel for what they’re doing by looking at the figures and graphs (I can’t read Chinese), but the math is above my pay grade. It seems counter-intuitive, but the research suggests a power supply that generates a pure sine wave might not be the best approach.

Ray K

diyrayk · 2021-01-08 3:26 am

Ugly said:
Is this 3rd harmonic "tuning" intended to compensate for to nonlinearity in the source, the load, or both?

Nonlinearity in the load.

Ray K

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Turntable Synchronous Motor AC Speed Control Driver (PSU) in Current Drive Mode ?

tiefbassuebertr

tiefbassuebertr

Pyramid

Ugly

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Ugly

tiefbassuebertr

diyrayk

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