Linn Lingo vs. Dr. Fuß or Square-Wave vs. Sine Wave Oscillator for Motor Control - Page 4 - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 10th July 2012, 11:05 PM   #31
diyAudio Member
 
Join Date: Feb 2006
Location: Willy, VIC
Quote:
Originally Posted by fvale View Post
This is a very interesting part of a article on a link kindly posted above by Tiefbassuebertr.<snip>
The article you quote was written by me some years ago. I have since learnt more about these motors and a couple of the assertions in the article need to be modified.

To the topic being discussed: in theory exact quadrature and equal phase voltages are ideal.

In practice, the ideal angle and voltage ratio for quietest operation will vary from motor to motor. As stated previously in this thread, the quietest drive I have been able to build had adjustable angle, phase voltage and third harmonic distortion.
  Reply With Quote
Old 11th July 2012, 07:22 PM   #32
volken is offline volken  Netherlands
diyAudio Member
 
Join Date: Jul 2004
Location: Nederlands
With a B@k accellerometer and a HP FFT Signal Analyzer unfortunately the horizontal span where different so its difficult too see the difference.
Next two current spectrum measurements are from the same motor both tuned with capacitor and resistor to correct the voltage about the two coils.
First on the mains supply 230 Volt the other on a clean powersupply made for idler turntables .
The mains has a lot pollution over here a clean supply gives a large sound improvement for this kind off turntables.

Volken
  Reply With Quote
Old 11th July 2012, 07:25 PM   #33
volken is offline volken  Netherlands
diyAudio Member
 
Join Date: Jul 2004
Location: Nederlands
And the measurements!
  Reply With Quote
Old 12th July 2012, 07:30 AM   #34
diyAudio Member
 
tiefbassuebertr's Avatar
 
Join Date: Jul 2005
Location: D-55629 Schwarzerden
Quote:
Originally Posted by volken View Post
I have done some vibration measurements on the motor for the Thorens TD160 also a two phase motor with capacitor for the second coil.
First picture is the motor with the original cap.0.15UF and second the tuned cap from 0.22uF .
The voltage about the two coils is not the same a difference from about 20 Volt in a next measurement I tune this with a resistor .

Volken
Quote:
Originally Posted by volken View Post
And the measurements!
Thank you for this files.

Last edited by tiefbassuebertr; 12th July 2012 at 07:32 AM.
  Reply With Quote
Old 15th July 2012, 04:19 AM   #35
diyAudio Member
 
Join Date: Aug 2010
Location: NYC
Question to Mark Kelly- does the 3rd harmonic 'flatten' the top/peak of the main wave form? It looked like it should on paper, and an Audacity recording of an Audacity track(60+180HZ at .1 the 60HZ level)seemed to confirm this(the leading edge was higher than the trailing, no idea why, but the peak was flattened). If so, assume this would produce smoother operation.
  Reply With Quote
Old 15th July 2012, 10:06 AM   #36
diyAudio Member
 
Join Date: Feb 2006
Location: Willy, VIC
Third harmonic can be in phase - tending to accentuate the peak of the primary wave, or antiphase - tending to flatten the peak. IIRC most motors responded best to a moderate amount of antiphase 3HD at low applied load.

My take on this is that the antiphase 3HD reduced the drive torque when the rotor was pulling in to the higher reluctance spots in the stator field and increased it as the rotor passed beyond this, thus effectively reducing the largest source of cogging in a synchronous motor (the variable reluctance of the stator field).

I'm currently focsussing on the way this effect changes as the angle between the rotor and the stator field changes.
  Reply With Quote
Old 15th July 2012, 09:55 PM   #37
diyAudio Member
 
Join Date: Aug 2010
Location: NYC
Thanks-was referring to anti-phase, the 180 negative and 60 positive lining up, and visa versa, if they start from a common zero point. Since pm synch motors operate in what Edgar Villchur called "a series of jerks"( Audio magazine article, Sept&Oct 1962, on the new AR turntable), moderating the "jerks" makes intuitive sense.

Intend to find a program which allows intro of 3rd HD, like Audacity, combined with precise phase control, like Cognaxon(currently using)-or,one that allows a waveform to be 'drawn' to suit. I have two spare cheap Hurst motors I can torment.

I assume these tricks will also help with hysteresis motors(have some ampex motors, Ashlands, to try) though not as dramatically;as far as I can tell, Villchur went with the then new pm motors on account of cost, as an undersized hysteresis motor could actually slow under load (whereas the pm would break synch), so a large, expensive motor would be required. He relied on the belt to filter out the cogging.
  Reply With Quote
Old 15th July 2012, 11:08 PM   #38
diyAudio Member
 
Join Date: Feb 2006
Location: Willy, VIC
Quote:
Originally Posted by rcthweatt View Post
Thanks-was referring to anti-phase, the 180 negative and 60 positive lining up, and visa versa, if they start from a common zero point. Since pm synch motors operate in what Edgar Villchur called "a series of jerks"( Audio magazine article, Sept&Oct 1962, on the new AR turntable), moderating the "jerks" makes intuitive sense.

Intend to find a program which allows intro of 3rd HD, like Audacity, combined with precise phase control, like Cognaxon(currently using)-or,one that allows a waveform to be 'drawn' to suit. I have two spare cheap Hurst motors I can torment.

I assume these tricks will also help with hysteresis motors(have some ampex motors, Ashlands, to try) though not as dramatically;as far as I can tell, Villchur went with the then new pm motors on account of cost, as an undersized hysteresis motor could actually slow under load (whereas the pm would break synch), so a large, expensive motor would be required. He relied on the belt to filter out the cogging.
Firstly, the "series of jerks" idea is totally misleading. If the stator field was perfectly uniform and the motor operates at its design torque there would be no torque ripple at all - both fields are sinusoidal, the torque is their vector multiple and is thus proportional to sine squared. The other coil is the cosine, sin squared plus cos squared = 1.

No, hysteresis motors are a totally different kettle of fish. No stator reluctance, torque spring effect quite prominent.
  Reply With Quote
Old 20th July 2012, 09:58 PM   #39
diyAudio Member
 
Join Date: Mar 2007
Location: Canandaigua, NY USA
"not dead on"- sorry, I just meant that the optimum value for minimum vibration would not be exactly the factory value, but it should come out quite close.
__________________
I may be barking up the wrong tree, but at least I'm barking!
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wanted: HP 209A Sine/Square Wave Oscillator scott17 Swap Meet 0 15th March 2012 02:58 AM
Sine wave - Square & Triangle wave generator using Transistors / OP-Amps lineup Solid State 20 9th October 2006 12:15 AM
Sine and square wave function generator Bricolo Parts 14 7th March 2003 11:45 PM


New To Site? Need Help?

All times are GMT. The time now is 07:54 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2