Thank you for your links
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I know most do not know motor in electronics.? I have also run cross 2 phase motors on some hard drives.?
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What I am look at size a brushless motor on my mini lathe that has a brush type motor torque at lower speeds.
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* One thing I noticed was some the manufacturer lathe using a brushless motor has 4 steps from 300 to 2,500 RPM.?
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* The DC brush used only 2 steps 1,000 next step 2,200 or 2,500 RPM.?
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* When saw that different it made me wonder on the decision on type.?
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I like a wide range control without changing belts. ?
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The brush type motors have greater torque as more power need but motor slows down. The control board just adds more voltage to keep the speed the same but increased the torque.?
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Now the brushless uses frequent to change speed.?
So torque says the same at high speed and low speed.?
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Finding graphic showing is a big problem to figure out the correct size replacement?
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Dave?
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On Fri, Jul 19, 2024 at 08:40 AM, WAM wrote:
No - still the same.? A great example of a sensorless is the DVD/CD
player - you can here it spin up, then drop to the proper RPM.
BLDC motors are electrically "commutated" with speed control via either
a sensor or back EMF.
where:
"There? are? two? torque? parameters? used? to? define? a
BLDC? motor,? peak? torque? (TP)? and? rated? torque
(TR). During continuous operations, the motor can be
loaded up to the rated torque.
In a BLDC motor, the torque remains constant for a
speed range up to the rated speed. The motor can be
run? up? to? the? maximum? speed,? which? can? be? up? to
150%?? of?? the?? rated?? speed,?? but?? the?? torque?? starts
dropping. "
Sensorless
Commutation methods:
Trapezoidal commutation:
FOC:
Sinusoidal control
My retrofit of using a Consew BLDC on a MaxNC CNC:
On my Deckel Clone:
On 7/19/2024 10:57 AM, robfliesrc via groups.io wrote:
I prefer to think of a BLDC motor as any other DC motor. The difference between a brushed and a brushless motor is simply that in a brushed motor the commutation is done mechanically by the combination of brushes and commutator, and in a brushless motor it is done by solid state electronics. Physically they work the opposite way, the coils are fixed and the magnets spin, but they are still governed by the same equations that link voltage, current, RPM, torque and efficiency using the same set of coefficients, only the typical values of those coefficients are different to reflect the different construction involved.
The advantage of a brushless motor is that it eliminates the moving parts involved in the commutator. The point of contact of the brushes can skip (leading to arcing), requiring a spring pressure and consequent resistance to turning (which can be reduced by material choice but not eliminated) and introduces electrical resistance that lowers the motor's efficiency under load compared to a well designed solid state commutator that has resistances in the low milliohms or even lower. Obviously wear of the brushes and commutator is not a factor. Also in the case of an "in-runner" brushless motor, the windings are glued to the outer case of the motor making it easy to conduct heat away from the windings.
There are 2 flavors of brushless motor. Some use a sensor (hall effect or optical) to detect the orientation of the magnets, they behave almost identically to brushed DC motors (except with typically higher efficiency), while sensorless brushless motors try to determine the position of the magnets based on the behavior of the windings and the voltage induced by the spinning magnets. This doesn't work well at low RPMs so sensorless brushless controllers use a startup mode that works without feedback initially (very much like a synchronous AC motor) until there is enough information coming back from the windings to allow proper commutation. Because of this. motors with sensors have better low RPM behavior and can start reliably at high torque. They cost a little more because of the additional cost of the sensor. (But sensorless motors have improved over the past 2 to 3 decades. so I might be overselling the difference.)
- Rob.
?
?
?
On Fri, Jul 19, 2024 at 08:40 AM, WAM wrote:
No - still the same.? A great example of a sensorless is the DVD/CD
player - you can here it spin up, then drop to the proper RPM.
BLDC motors are electrically "commutated" with speed control via either
a sensor or back EMF.
where:
"There? are? two? torque? parameters? used? to? define? a
BLDC? motor,? peak? torque? (TP)? and? rated? torque
(TR). During continuous operations, the motor can be
loaded up to the rated torque.
In a BLDC motor, the torque remains constant for a
speed range up to the rated speed. The motor can be
run? up? to? the? maximum? speed,? which? can? be? up? to
150%?? of?? the?? rated?? speed,?? but?? the?? torque?? starts
dropping. "
Sensorless
Commutation methods:
Trapezoidal commutation:
FOC:
Sinusoidal control
My retrofit of using a Consew BLDC on a MaxNC CNC:
On my Deckel Clone:
On 7/19/2024 10:57 AM, robfliesrc via groups.io wrote:
I prefer to think of a BLDC motor as any other DC motor. The difference between a brushed and a brushless motor is simply that in a brushed motor the commutation is done mechanically by the combination of brushes and commutator, and in a brushless motor it is done by solid state electronics. Physically they work the opposite way, the coils are fixed and the magnets spin, but they are still governed by the same equations that link voltage, current, RPM, torque and efficiency using the same set of coefficients, only the typical values of those coefficients are different to reflect the different construction involved.
The advantage of a brushless motor is that it eliminates the moving parts involved in the commutator. The point of contact of the brushes can skip (leading to arcing), requiring a spring pressure and consequent resistance to turning (which can be reduced by material choice but not eliminated) and introduces electrical resistance that lowers the motor's efficiency under load compared to a well designed solid state commutator that has resistances in the low milliohms or even lower. Obviously wear of the brushes and commutator is not a factor. Also in the case of an "in-runner" brushless motor, the windings are glued to the outer case of the motor making it easy to conduct heat away from the windings.
There are 2 flavors of brushless motor. Some use a sensor (hall effect or optical) to detect the orientation of the magnets, they behave almost identically to brushed DC motors (except with typically higher efficiency), while sensorless brushless motors try to determine the position of the magnets based on the behavior of the windings and the voltage induced by the spinning magnets. This doesn't work well at low RPMs so sensorless brushless controllers use a startup mode that works without feedback initially (very much like a synchronous AC motor) until there is enough information coming back from the windings to allow proper commutation. Because of this. motors with sensors have better low RPM behavior and can start reliably at high torque. They cost a little more because of the additional cost of the sensor. (But sensorless motors have improved over the past 2 to 3 decades. so I might be overselling the difference.)
- Rob.
?
?
On Fri, Jul 19, 2024 at 08:40 AM, WAM wrote:
No - still the same.? A great example of a sensorless is the DVD/CD
player - you can here it spin up, then drop to the proper RPM.
BLDC motors are electrically "commutated" with speed control via either
a sensor or back EMF.
where:
"There? are? two? torque? parameters? used? to? define? a
BLDC? motor,? peak? torque? (TP)? and? rated? torque
(TR). During continuous operations, the motor can be
loaded up to the rated torque.
In a BLDC motor, the torque remains constant for a
speed range up to the rated speed. The motor can be
run? up? to? the? maximum? speed,? which? can? be? up? to
150%?? of?? the?? rated?? speed,?? but?? the?? torque?? starts
dropping. "
Sensorless
Commutation methods:
Trapezoidal commutation:
FOC:
Sinusoidal control
My retrofit of using a Consew BLDC on a MaxNC CNC:
On my Deckel Clone:
On 7/19/2024 10:57 AM, robfliesrc via groups.io wrote:
I prefer to think of a BLDC motor as any other DC motor. The difference between a brushed and a brushless motor is simply that in a brushed motor the commutation is done mechanically by the combination of brushes and commutator, and in a brushless motor it is done by solid state electronics. Physically they work the opposite way, the coils are fixed and the magnets spin, but they are still governed by the same equations that link voltage, current, RPM, torque and efficiency using the same set of coefficients, only the typical values of those coefficients are different to reflect the different construction involved.
The advantage of a brushless motor is that it eliminates the moving parts involved in the commutator. The point of contact of the brushes can skip (leading to arcing), requiring a spring pressure and consequent resistance to turning (which can be reduced by material choice but not eliminated) and introduces electrical resistance that lowers the motor's efficiency under load compared to a well designed solid state commutator that has resistances in the low milliohms or even lower. Obviously wear of the brushes and commutator is not a factor. Also in the case of an "in-runner" brushless motor, the windings are glued to the outer case of the motor making it easy to conduct heat away from the windings.
There are 2 flavors of brushless motor. Some use a sensor (hall effect or optical) to detect the orientation of the magnets, they behave almost identically to brushed DC motors (except with typically higher efficiency), while sensorless brushless motors try to determine the position of the magnets based on the behavior of the windings and the voltage induced by the spinning magnets. This doesn't work well at low RPMs so sensorless brushless controllers use a startup mode that works without feedback initially (very much like a synchronous AC motor) until there is enough information coming back from the windings to allow proper commutation. Because of this. motors with sensors have better low RPM behavior and can start reliably at high torque. They cost a little more because of the additional cost of the sensor. (But sensorless motors have improved over the past 2 to 3 decades. so I might be overselling the difference.)
- Rob.
davesmith1800