"Don Kelly" wrote in message news:LGess.24063$Sm5.email@example.com...
On 23/11/2012 11:58 PM, Lord Androcles, Zeroth Earl of Medway wrote: > "Don Kelly" wrote in message news:ExZrs.12238$nO.firstname.lastname@example.org... > > On 22/11/2012 7:49 PM, Timothy Sutter wrote: >> Don Kelly wrote: >> >>> Timothy Sutter wrote: >> >>>> Archimedes Plutonium wrote: >> >>>>> Timothy Sutter wrote: >> >>>>>>>> and, it really does seem as if >>>>>>>> the little whizzers =DO= -have- "flight paths" >>>>>>>> and that they are -not- simply in >>>>>>>> 10000000000000000000000000000000000000000 >>>>>>>> places at the same time.... >> >>>>>>> just look at these images... >>>>>>> http://en.wikipedia.org/wiki/File:Various_Spirograph_Designs.jpg >>>>>>> see, you don't just see the cloud of uncertainty >>>>>>> you see distinctly flight paths... >> >>>>>> the thing about the spirograph images is that they are =flat= >> >>>>>> and the atom travails in -volume- and so, 3D images >>>>>> and you really would wonder if the shapes of snowflakes -are- >>>>>> sort of like the shapes of certain electronic flight paths... >>>>>> "but isn't i true that no two snowflakes are alike?" >>>>>> have you really looked at all of them? >> >>>>>> STOP >> >>>>> Hi Tim, I will stop for 3d volume. >> >>>>> It has been a long time since I took apart an electric motor of its >>>>> windings of copper wire. >> >>>>> Tell me, are the windings close to being spherical in all? And are the >>>>> windings of 1 long copper wire or are they of 2 long copper wires or >>>>> more? >> >>>> i just happen to have the motor of >>>> an olde box window fan in the basement. >> >>>> it's a lot of copper wire and these things called >>>> "bushings" that seem to be copper as well. >> >>>> it doesn't look too much like this one >>>> but it resembles it a little bit. >> >>> The box fan motor is likely a single phase shaded pole induction motor. >>> Such a motor will have no commutator as shown in your permanent magnet >>> DC motor (it also will not have permanent magnets and the rotor will be >>> quite different in general). >> >> i'm pretty sure i said they didn't look too much alike >> but had a little bit of similarity, and, i still say that now. >> >> my new fan has a fairly small motor with a diameter >> of about 5 inches and no exposed copper, but my >> old fan motor was larger and you could see blobs >> of copper wiring -somewhat- like that scooter motor. > Your new fan, considering its size may be a "brushless DC" motor - it > too will have coils. >> >> just seeing the copper coils is a similarity. > Yes- there is a similarity- the same as the similarity to a solenoid and > a transformer. seeing copper coils in a transformer >> >> >>> The "bushings" are "oilite (sic?)" bearings which are >>> typically copper or a copper alloy which is sintered and holds oil. >> >> my old fan may have had this little felt tipped >> front end where you had to oil every so often. > That figures. >> >>> They are cheaper than ball bearings but don't generally last as >>> well.. However, these bushings have nothing to do with the >>> electrical/magnetic operation of the motor. >> >> it's possible that these old bushings were carbon >> and would crud up after a while and you'd have >> to clean up the crud. > Doubtful. However graphite has been used as a lubricant. Sintered bronze > is common. >> >> maybe i'll dig it out and take it apart unless >> i already disposed of it in an enVIromentally safe manner. >> >>> As for Archie's question- No- the windings are not spherical at all. >> >> no, many coils are sort of round or cylindrical and not spheres. >> i have an olde starter motor that may be a -little- bit more >> like the scooter motor, but i'm, not in the mood to take >> it apart right now, as, it is greasy and secure where >> it is on its little shelf. > Cylindrical is common and practical."sort of round" is meaningless. > >> >> >>> As usual he is off in his own little world -where facts are not >>> important. >> >> >> well, yon Pluto does -ask- if the windings are spherical >> Pluto doesn't exactly tell me what sort of motor >> i have and then tell me how it's constructed. > If I am wrong- let me know. > Fan- typically 120V (240V in UK) -assumed not to be a new fan (you said > old(e)) so what is typical? A form of small induction motor-with coils > on the stator. If it is a DC motor, then the construction will be > essentially the same as the scooter motor with coils on the rotor and a > commutator. The presence of a commutator is a give-away. >> > -----rant snipped------ > > ====================================================== > If DC then even 30 years old it'll be brushless, floppy drives have come > and gone long ago, Don. > http://en.wikipedia.org/wiki/File:Floppy_drive_spindle_motor_open.jpg > The fan on my computer is variable speed, it speeds up if the processor > gets hot and slows to reduce noise. > It's difficult to imagine any young engineer designing a commutator in > 2012 or any entrepreneur investing in one when it can be made on a chip. > I have a TV on a dongle and if you want power just look at the microwave > oven, it's a low to high frequency converter at over one horsepower. > > -- This message is brought to you from the keyboard of > Lord Androcles, Zeroth Earl of Medway > > I think that we may be involved in a case of terminology. To me, a box fan is a fan, run from a 60Hz 120/240V system or a 50Hz 240V system, which is in a square enclosure and is used for room cooling. Many are portable and will have shaded pole induction motors and have some speed control (3 settings typically) which may simply be switching steps on an autotransformer or by control of a triac. These are cheap and reliable- although bearings can be a problem. This is what I assumed that he was looking at and trying to compare to a commutator motor.
I would use "case fan" for the ones used in a computer and, yes, these are 'brushless DC' with electronic commutation of what is essentially an AC synchronous machine or a stepper. My comments did not refer to these but the resemblance that was mentioned is only that all have windings.
As to the conventional commutator machine- these are still in use and are dying out as better power electronic switching makes it possible to eliminate the mechanical commutator which limits the practical upper size of DC machines and is a major maintenance problem. I do note that they are still in use in many applications -e.g. the series DC motor used as a car starter- where the inherent behaviour is preferable. I also note that large inverter drives supply AC machines- mostly induction machines.
I am also quite prepared to say that I don't actually know what kind of fan and wha was its use -so that I just referred to what I call a "box fan" as above. ==================================================== Ok, we are almost completely in agreement. I've never come across a triac or autotransformer controlled induction motor though. That would be like trying to control a fluorescent lamp. Multi-speed ceiling fans with induction motors have two windings, one of which can be switch configured as a 4-pole or 8-pole (2-pole is much too fast for a ceiling fan) and the other a 12-pole in a 24-slot stator. What has really made today's speed control possible is permanent magnet technology with modern alloys. No need for the old Ward Leonard system, some still used on old elevators. What I've not been able to discover is the speed control of trains on 750V DC third rail, they sound like they have gear boxes. Maybe its to reduce starting current.
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