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

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 .

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

DC permanent magnet motors: brushed vs. brushless
 

"Ned Simmons" wrote in message
...
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

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

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.

DC permanent magnet motors: brushed vs. brushless
 

On Thu, 3 Mar 2011 16:50:46 -0800, "Artemus"
wrote:


"Ned Simmons" wrote in message
.. .
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)