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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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DC permanent magnet motors: brushed vs. brushless
Just curious about treadmill motors.
Most treadmill motors I've seen are brushed. Is it likely that newer ones are brushless, and if so, are the electronics that make the motor brushless internal or external to the motor, and how would I tell? I'd hate to find out a motor is brushless, and that I threw away the goddamm electronics..... Couldn't treadmills use AC permenant magnet motors? Aren't they a little simpler than the DC? It seems that the older DC treadmill motors, altho rated lower in power than modern treadmill motors, pack a lot more punch to them. No surprise. -- EA |
#2
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DC permanent magnet motors: brushed vs. brushless
On Wed, 2 Mar 2011 22:26:21 -0500, "Existential Angst"
wrote: Just curious about treadmill motors. Most treadmill motors I've seen are brushed. Is it likely that newer ones are brushless, and if so, are the electronics that make the motor brushless internal or external to the motor, and how would I tell? I'd hate to find out a motor is brushless, and that I threw away the goddamm electronics..... Couldn't treadmills use AC permenant magnet motors? Aren't they a little simpler than the DC? It seems that the older DC treadmill motors, altho rated lower in power than modern treadmill motors, pack a lot more punch to them. No surprise. So far I've not seen a brushless DC treadmill motor, but I have not looked at any really new high end units. For a permanent magnet AC motor you are talking a synchronous or stepper motor I assume - the drive circuit is more complex . |
#3
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DC permanent magnet motors: brushed vs. brushless
On Wed, 02 Mar 2011 22:26:21 -0500, Existential Angst wrote:
Just curious about treadmill motors. Most treadmill motors I've seen are brushed. Is it likely that newer ones are brushless, and if so, are the electronics that make the motor brushless internal or external to the motor, and how would I tell? Normally they're external to the motor, but I've seen purpose-built brushless motors that have the electronics built in. I wouldn't expect that here. The vast majority of brushless motors are three phase, and will have three (or very slightly possibly four) big wires coming out. Brushless motors that have to be well controlled all the way down to a stop will also have additional sensors -- for a treadmill, I'd expect three Hall sensors, which would mean five to nine little wires coming out of the motor. So: two wires means it's brushed, or brushless with internal electronics. Three heavy wires and five light wires almost certainly means it's brushless and it has external control. Ditto three heavy wires alone. Other combinations of wires -- who knows? I'd hate to find out a motor is brushless, and that I threw away the goddamm electronics..... That would be a pain. Couldn't treadmills use AC permenant magnet motors? Aren't they a little simpler than the DC? There's not a whole lot of difference between an "AC permanent magnet motor" and a "DC brushless motor". The big difference is that an "AC PM" motor has a sinusoidal voltage characteristic as it spins, and really likes to be presented with a sinusoidal voltage on each wire to make it go. A "brushless DC" motor has a voltage characteristic on each coil that's more trapezoidal, and you can match the flat tops of the trapezoids with the DC voltage that's switched in and out. So while it may be more complicated to _make_ a brushless DC motor, it's certainly easier to _drive_ one. It seems that the older DC treadmill motors, altho rated lower in power than modern treadmill motors, pack a lot more punch to them. No surprise. Who'd a thunk? :-). -- http://www.wescottdesign.com |
#4
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DC permanent magnet motors: brushed vs. brushless
I believe you'll find that home-use treadmills will typically have DC PM
motors, with rectifiers (or other semiconductors) outputting DC from about 90V to slightly higher DC voltages. PM motors are generally significantly more compact than the equivalent HP rating AC induction motor, and the RPMs can be much higher than many common AC induction motors. AC PM motors don't exist, as far as I know. Even weed string trimmer motors will utilize one diode for DC, when a PM motor is utilized, which is all that's required without variable speed regulation. A rectifier/diode after a variac (for example) will provide variable speed, but not speed regulation. The speed control trigger switch from a corded (not cordless) variable speed drill motor will provide variable speed in smaller universal (and likely small, rectified DC PM) motors such as Dremel or die grinder motors.. some of the foot-pedal speed controls use exactly the same trigger switch, rated to about 6 amps, IIRC. HF and other vendors have variable speed controls for routers/etc that utilize a fairly simple triac/diac circuit (can be found at various electronic sites online). If choosing the router control from China, I'd recommend checking all of the internal connections before use, as 2 of 'em that I bought had very weak/pop-off soldered connections inside. Universal motors (routers, grinders, corded drill motors etc) can be operated with AC or DC, but have wound field/stator coils, not magnets, as far as I've seen. There were some treadmills with 3-phase AC induction motors, which use a VFD to convert 120VAC power to 3-phase (yes, 120VAC single-phase input 3-phase output does exist).. I have one I picked up at a hamfest, but can't remember the name. Some A.O. Smith motors are the same type, typically for special purpose applications - expensive. I don't have any experience with the newer brushless DC motors other than small fans like those used for PC case and CPU cooling fans. If you want a seriously reliable DC PM motor for a machine application, find a surplus new/good condition Leeson, Baldor, etc TEFC ball bearing motor (for which spare brushes are available), and use a KB or similar DC controller that will provide excellent speed regulation (won't slow down with varying loads.. *and motor protection* that cheaper DC motor circuits may not/likely not provide. -- WB .......... "Existential Angst" wrote in message ... Just curious about treadmill motors. Most treadmill motors I've seen are brushed. Is it likely that newer ones are brushless, and if so, are the electronics that make the motor brushless internal or external to the motor, and how would I tell? I'd hate to find out a motor is brushless, and that I threw away the goddamm electronics..... Couldn't treadmills use AC permenant magnet motors? Aren't they a little simpler than the DC? It seems that the older DC treadmill motors, altho rated lower in power than modern treadmill motors, pack a lot more punch to them. No surprise. -- EA |
#5
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DC permanent magnet motors: brushed vs. brushless
On 3/2/2011 7:26 PM, Existential Angst wrote:
Just curious about treadmill motors. Most treadmill motors I've seen are brushed. Is it likely that newer ones are brushless, and if so, are the electronics that make the motor brushless internal or external to the motor, and how would I tell? I'd hate to find out a motor is brushless, and that I threw away the goddamm electronics..... Couldn't treadmills use AC permenant magnet motors? Aren't they a little simpler than the DC? It seems that the older DC treadmill motors, altho rated lower in power than modern treadmill motors, pack a lot more punch to them. No surprise. please explain "AC PM MOTOR" - how could this possibly work? There are polyphase motors that use a PM, but they are usually called "brushless DC motors" - there is no inherent reason why they could not have a diode bridge at their input so they could run on AC as well, but that does not seem to be what you are talking about. You do understand the basics of how a motor works by magnetic attraction, right? -- www.wbnoble.com |
#6
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DC permanent magnet motors: brushed vs. brushless
"Existential Angst" fired this volley in
: It seems that the older DC treadmill motors, altho rated lower in power than modern treadmill motors, pack a lot more punch to them. No surprise. I dunno. I just snagged a PM motor from a six-year-old treadmill that's rated at 2HP, and it has mountains of torque at virtually zero speed. About the only thing "ugly" about it is the bearings aren't the best. That can be remedied. LLoyd |
#7
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DC permanent magnet motors: brushed vs. brushless
Bill Noble fired this volley in news:ikncl8$552$1
@news.eternal-september.org: You do understand the basics of how a motor works by magnetic attraction, right? Oh, Bill, you're going to raise a lot of questions about that one! G LLoyd |
#8
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DC permanent magnet motors: brushed vs. brushless
On Mar 3, 12:52*am, "Wild_Bill" wrote:
... AC PM motors don't exist, as far as I know. ... See Tim Wescott's reply. Segways use 3 phase AC motors with an -extremely- strong permanent magnet rotor. They stick to the sheet metal of lab benches so hard the bench slides before they pull loose. http://www.moonbasecafe.com/summativ...2/science.html jsw |
#9
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DC permanent magnet motors: brushed vs. brushless
Jim, I think that means I won't be seeing one any time soon, inside
something that I might take apart. I don't recall if 3-phase VRC drum motors have permanent magnets, although the capstan motors do, but I was thinking in terms of motors that do real work/machine power in my earlier reply. -- WB .......... "Jim Wilkins" wrote in message ... On Mar 3, 12:52 am, "Wild_Bill" wrote: ... AC PM motors don't exist, as far as I know. ... See Tim Wescott's reply. Segways use 3 phase AC motors with an -extremely- strong permanent magnet rotor. They stick to the sheet metal of lab benches so hard the bench slides before they pull loose. http://www.moonbasecafe.com/summativ...2/science.html jsw |
#10
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DC permanent magnet motors: brushed vs. brushless
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message I dunno. I just snagged a PM motor from a six-year-old treadmill that's rated at 2HP, and it has mountains of torque at virtually zero speed. About the only thing "ugly" about it is the bearings aren't the best. That can be remedied. LLoyd Where did you get a pulley to fit the 17mm shaft? Art |
#11
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DC permanent magnet motors: brushed vs. brushless
"Artemus" fired this volley in news:ikp5i6$bd6$1
@news.eternal-september.org: Where did you get a pulley to fit the 17mm shaft? Art In my particular case, any pulley with "enough" hub is the right size. I turn anything I need to fit. (This is a metalworking sig... right?) LLoyd |
#12
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DC permanent magnet motors: brushed vs. brushless
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message . 3.70... "Artemus" fired this volley in news:ikp5i6$bd6$1 @news.eternal-september.org: Where did you get a pulley to fit the 17mm shaft? Art In my particular case, any pulley with "enough" hub is the right size. I turn anything I need to fit. (This is a metalworking sig... right?) LLoyd Right. I have a few of those motors but unfortunately no lathe. Art |
#13
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DC permanent magnet motors: brushed vs. brushless
Wild_Bill wrote:
... use a KB or similar DC controller that will provide excellent speed regulation (won't slow down with varying loads.. .... I have a KB controller on a treadmill motor that drives my belt grinder. I get a lot of slow-down on heavy loads. For real speed regulation, use tach feedback and a servo amp. Bob |
#14
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DC permanent magnet motors: brushed vs. brushless
On Thu, 3 Mar 2011 15:31:46 -0800, "Artemus"
wrote: "Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message .3.70... "Artemus" fired this volley in news:ikp5i6$bd6$1 @news.eternal-september.org: Where did you get a pulley to fit the 17mm shaft? Art In my particular case, any pulley with "enough" hub is the right size. I turn anything I need to fit. (This is a metalworking sig... right?) LLoyd Right. I have a few of those motors but unfortunately no lathe. Art Misumi will bore and key many different pulleys to 17mm. For example: http://us.misumi-ec.com/us/ItemDetail/10300405670.html -- Ned Simmons |
#15
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DC permanent magnet motors: brushed vs. brushless
Wild_Bill wrote:
AC PM motors don't exist, as far as I know. Even weed string trimmer motors will utilize one diode for DC, when a PM motor is utilized, which is all that's required without variable speed regulation. A rectifier/diode after a variac (for example) will provide variable speed, but not speed regulation. FWIW, I once found one of those leaf blowers in the dumpster. I took it home and took it apart - the plastic brush holders were melted. It had a full-wave bridge rectifier (4 diodes). Got a couple of way kewl magnets out of it! ;-) Cheers! Rich |
#16
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DC permanent magnet motors: brushed vs. brushless
On Thu, 03 Mar 2011 18:55:04 -0500, Bob Engelhardt
wrote: Wild_Bill wrote: ... use a KB or similar DC controller that will provide excellent speed regulation (won't slow down with varying loads.. ... I have a KB controller on a treadmill motor that drives my belt grinder. I get a lot of slow-down on heavy loads. For real speed regulation, use tach feedback and a servo amp. Aren't treadmill motors series wound? If so, I'm not surprised the KB controller doesn't work very well. Their speed regulation is quite good with PM and shunt wound motors, as long as the proper HP resistor is installed. -- Ned Simmons |
#17
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DC permanent magnet motors: brushed vs. brushless
"Ned Simmons" wrote in message ... On Thu, 3 Mar 2011 15:31:46 -0800, "Artemus" wrote: "Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message .3.70... "Artemus" fired this volley in news:ikp5i6$bd6$1 @news.eternal-september.org: Where did you get a pulley to fit the 17mm shaft? Art In my particular case, any pulley with "enough" hub is the right size. I turn anything I need to fit. (This is a metalworking sig... right?) LLoyd Right. I have a few of those motors but unfortunately no lathe. Art Misumi will bore and key many different pulleys to 17mm. For example: http://us.misumi-ec.com/us/ItemDetail/10300405670.html -- Ned Simmons Thanks for that link. I checked and unfortunately they don't have any V belt pulleys. Art |
#18
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DC permanent magnet motors: brushed vs. brushless
"Ned Simmons" wrote in message news On Thu, 03 Mar 2011 18:55:04 -0500, Bob Engelhardt wrote: Wild_Bill wrote: ... use a KB or similar DC controller that will provide excellent speed regulation (won't slow down with varying loads.. ... I have a KB controller on a treadmill motor that drives my belt grinder. I get a lot of slow-down on heavy loads. For real speed regulation, use tach feedback and a servo amp. Aren't treadmill motors series wound? If so, I'm not surprised the KB controller doesn't work very well. Their speed regulation is quite good with PM and shunt wound motors, as long as the proper HP resistor is installed. -- Ned Simmons All the TM motors I have, and have seen, are the PM type. Art |
#19
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DC permanent magnet motors: brushed vs. brushless
"Artemus" fired this volley in news:ikpcvj$se$1
@news.eternal-september.org: Thanks for that link. I checked and unfortunately they don't have any V belt pulleys. That's because most of those motors run poly-V or timing belts. LLoyd |
#20
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DC permanent magnet motors: brushed vs. brushless
On Thu, 03 Mar 2011 19:20:41 -0500, Ned Simmons
wrote: On Thu, 03 Mar 2011 18:55:04 -0500, Bob Engelhardt wrote: Wild_Bill wrote: ... use a KB or similar DC controller that will provide excellent speed regulation (won't slow down with varying loads.. ... I have a KB controller on a treadmill motor that drives my belt grinder. I get a lot of slow-down on heavy loads. For real speed regulation, use tach feedback and a servo amp. Aren't treadmill motors series wound? If so, I'm not surprised the KB controller doesn't work very well. Their speed regulation is quite good with PM and shunt wound motors, as long as the proper HP resistor is installed. Some are series, some are shunt, and the VAST majority are PM. |
#21
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DC permanent magnet motors: brushed vs. brushless
On Thu, 3 Mar 2011 16:50:46 -0800, "Artemus"
wrote: "Ned Simmons" wrote in message news On Thu, 03 Mar 2011 18:55:04 -0500, Bob Engelhardt wrote: Wild_Bill wrote: ... use a KB or similar DC controller that will provide excellent speed regulation (won't slow down with varying loads.. ... I have a KB controller on a treadmill motor that drives my belt grinder. I get a lot of slow-down on heavy loads. For real speed regulation, use tach feedback and a servo amp. Aren't treadmill motors series wound? If so, I'm not surprised the KB controller doesn't work very well. Their speed regulation is quite good with PM and shunt wound motors, as long as the proper HP resistor is installed. -- Ned Simmons All the TM motors I have, and have seen, are the PM type. Art I have a beautiful GE series wound motor from a treadmill - along with the controller for it. It has VERY good speed regulation (It has a tachometer feedback) |
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