 Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me. |
Forum Index : Windmills : How F&P decogged their new motor.
| Author | Message | ||||
Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Discovered something interresting tonight. I had a new 48 magnet hub, the one we use for the 7 phase conversion, that had collected some iron dust. The dust had settled along the edge of the magnets. Look at the shape..... 
These arrow shaped magnets have the same effect as skewed or angled magnets. This would explain how F&P have reduced cogging on their new motors. The new motor is still a 3 phase motor, but as well as using less magnets, also has less poles, only 36. These new 36 pole stators wont appear on the junk piles for a couple of years, so the 7 phase will be the best option till then. Here's a snippet of info from this interresting article some posted a couple of weeks ago http://www.appliancemagazine.com/zones/supplier/18_motor_mfg /editorial.php?article=1561&zone=18&first=1 "Finally, the company changed the number of magnetic poles on the rotor in relation to the wound poles on the stator, which changed the ratio from 42:56 to 36:48 poles to reduce the cogging torque." Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
||||
| clarence Regular Member  Joined: 27/10/2006 Location: Posts: 63 |
Wow! that is interesting. I wonder how much a new 36 pole stator is worth. |
||||
Megawatt Man Senior Member  Joined: 03/05/2006 Location: AustraliaPosts: 119 |
Great work, Glenn. They had to use 36 poles on the new stator to maintain a three phase drive system. But how innovative to make curly poles! Kiwis can think too! I must sit and calculate the spatial coincidence of the new rotor poles with the new stator poles. More fun! Megawatt Man |
||||
| Megawatt Man Senior Member Joined: 03/05/2006 Location: AustraliaPosts: 119 |
Hello Gentlemen and Ladies I hope! The table below shows the number of rotary and stationary poles that are exactly coincident in F&Ps with different combinations of rotors and stators. It highlights reasons for more and less cogging. First, the Gizmo 3 (the original combination, a 3 phase machine) had plenty of cogging and even more if neos were used. At any time there are 14 magnets exactly opposite stator poles. Next, the Gizmo 7 (the 7 phase arrangement Gizmo came up with) only had 8 coincident poles, so it could be expected to have less cogging. But the other factor he just discovered, that the magnets are skewed, means even less cogging is produced. Now, the latest F&P arrangement has 12 coincident poles but the magnets are skewed and reports are that there is no cogging. (The article Gizmo highlighted in the US mags also talked about F&P achieving less input power – maybe that means that the new machines will have greater limitations on alternator output power – remains to be seen) Number of rotary and stationary poles exactly coincident, combinations of F&Ps ROTOR 56 poles, OLD 48 poles, NEW STATOR 42 poles, OLD 14, Gizmo 3 8, Gizmo 7 36 poles, NEW N/A 12, skewed Now brucedownunder2 made a 48 pole rotor with lots of neos, but it cogged, even though there were only 8 coincident poles. The reason was that the neos provided a much stronger field. I reckon it would be just as strong if he had arranged the two rows of neos so they produced a V shaped field, equivalent to skewing, like the new rotors do. Cogging would be reduced, but I cannot tell by how much but of course would love to know. You will have noted that Highlander is doing an adventurous experiment in skewing of a stator and that will prove something about cogging, I reckon close to the same result achieved lately by F&P. For more comparisons, I would love to see the Volts x Amps output for a Gizmo3 and a Gizmo 7 with identical wind speeds. That would be another very helpful piece of info. Have a great weekend, especially in Mackay. Megawatt Man |
||||
| Megawatt Man Senior Member Joined: 03/05/2006 Location: AustraliaPosts: 119 |
Sorry Folks can't format to produce tqble gridlines. Imagine the last line on entries is tabbed across so the 36 is under the 42. Megawatt Man |
||||
 Print this page |
