Coreless Brushed dc motor Designing
- Thread starter big
- Start date
Lebowski
10 MW
This, spinning at 3000 rpm, would get you 6kW (its brushless though, so just to give you some ideas):
http://endless-sphere.com/forums/viewtopic.php?f=30&t=46476
http://endless-sphere.com/forums/viewtopic.php?f=30&t=46476
Before we can do much to help, we need to know where you are starting from.big said:
How many motors have you designed so far?
How much do you know about how they work, and what makes each type do what it does?
And then: is there a specific reason you want to make this specific type?
These are my answers to your questions,
-I am an Electrical and Electronics Engineer with an grad Degree.
-Have build ,Rather i would say Copied a motor design to build a new model.
-But never design a motor from scratch,
I know I don't have any fancy experience with motors but I am dedicated in building this one.
Main reason of building an Motor is to keep the building cost to minimal-My Main Moto is - SUPER CHEAP Coreless Motor.
With 90+ Efficiency.
-I am an Electrical and Electronics Engineer with an grad Degree.
-Have build ,Rather i would say Copied a motor design to build a new model.
-But never design a motor from scratch,
I know I don't have any fancy experience with motors but I am dedicated in building this one.
Main reason of building an Motor is to keep the building cost to minimal-My Main Moto is - SUPER CHEAP Coreless Motor.
With 90+ Efficiency.
major
10 kW
big said:
I don't understand your motivation for coreless brushed. It will not be inexpensive. I have seen a number of such designs over the years primarily for applications requiring low inertia rotors which commanded a premium cost to achieve that. A radial flux design is shown in US Patent #3,343,017 and an axial in #3,480,815 to give you an idea of what those machines looked like. Note the resemblance or the axial winding to that of the Agni motors (which have steel in the armature).
liveforphysics
100 TW
A poor topology to choose for someone looking for high efficiency in your power levels for low cost.
The Main Motive to build a Coreless motor is for its Efficiency, Precise control on Acceleration and Light Weight ;Since There is no rotor inertia(Very Less as compared to Generic BLDC.
If there is a BLDC motor that falls under the catagory of 90~95% Efficiency then I would surely go to build that,Since Stators from AC motors are easily available.
If there is a BLDC motor that falls under the catagory of 90~95% Efficiency then I would surely go to build that,Since Stators from AC motors are easily available.
Honk
100 W
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- Oct 10, 2011
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- 230
Well, I couldn't recommend a coreless motor if efficiency is one of your goals.big said:
The drawback of a coreless design is much lower fluxlevel through the windings.
Less flux requires more turns and this increases I2R losses to much unless you
are looking for a fast spinning design, e'g 10K rpm or higher.
But as usual....you have to calculate everything before building it.
Calculate average flux by numerous magnetic programs found on the web.
Then calc the motor layout and turns needed for the required rpm.
Now you can calculate the wire resistance and I2R losses.
Here's a formula you can start playing with.
(N * A * R * B * P) = Slot Volt * Slots per phase = Phase Volt * 1.732 = AC output x 1.41 = DC voltage
N = number of winding turns per teeth.
A = area of one magnet ( in square meters )
R = revolutions per second, aka RPS
B = average magnetic strength in Tesla
P = number of magnets used
speedmd
10 MW
Would PC board type fit your requirements. Light weight for certain.
Now we are going some were.
@ Honk
First of, I have read on the web that the most efficient type of Motor is a Coreless DC Motors and they have generally high torque if designed correctly.
And apart from that I am looking to build the rotor in a diametric value of 6 ~ 8" OD.
What is the easy software to get the model of motor flux density.
@speedmd
@ Honk
First of, I have read on the web that the most efficient type of Motor is a Coreless DC Motors and they have generally high torque if designed correctly.
And apart from that I am looking to build the rotor in a diametric value of 6 ~ 8" OD.
What is the easy software to get the model of motor flux density.
@speedmd
Possibly that to can work unless the efficiency and torque is great enough.
Honk
100 W
- Joined
- Oct 10, 2011
- Messages
- 230
The only coreless design I can think of (at your goals) is an axial flux motor.
This lets high flux pass through the windings as there is magnets on both sides of the coils.
It can easily be stacked as a pile of pancakes for the required power level.
Aka the name...pancake motor.
Please have a look at Lebowskis motor
Flux calculations depend entirely on the shape of your magnets. Pancake motors are easy due to their layout.
If they are standard rectangular or round magnets then you can use almost any of the calculator found at the web.
Just input Magnet size, Magnet grade and distance between magnets.
Just google "magnetic calculator"
PS, you should use Litz wire in all motors where the flux is passing directly though the windings.
If not you will face increased losses in form of eddy currents in the windings. DS
This lets high flux pass through the windings as there is magnets on both sides of the coils.
It can easily be stacked as a pile of pancakes for the required power level.
Aka the name...pancake motor.
Please have a look at Lebowskis motor
Flux calculations depend entirely on the shape of your magnets. Pancake motors are easy due to their layout.
If they are standard rectangular or round magnets then you can use almost any of the calculator found at the web.
Just input Magnet size, Magnet grade and distance between magnets.
Just google "magnetic calculator"
PS, you should use Litz wire in all motors where the flux is passing directly though the windings.
If not you will face increased losses in form of eddy currents in the windings. DS
@ Honk
Now that a good start Honk,I really Appreciate your help brother.I just need to go through PANKCAKE type motor as suggested.And I have gone through litz wire ,and I would hop to build it via using high gauge enameled copper winding wires to build the cable bunch for the rotor winding.I hope that would reduce Eddy Current and increase flux density.
And I have Gone through Lebowski's Motor and I found it to be Brush less and I am planing to build a brushed type,Since I would be able to go with low cost and simple Brushed controller than 3 phase complex controller for the motor.
Now that a good start Honk,I really Appreciate your help brother.I just need to go through PANKCAKE type motor as suggested.And I have gone through litz wire ,and I would hop to build it via using high gauge enameled copper winding wires to build the cable bunch for the rotor winding.I hope that would reduce Eddy Current and increase flux density.
And I have Gone through Lebowski's Motor and I found it to be Brush less and I am planing to build a brushed type,Since I would be able to go with low cost and simple Brushed controller than 3 phase complex controller for the motor.
Honk
100 W
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- Oct 10, 2011
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- 230
You can build a brushed pancake motor. No problems except more mechanical work.
Just reverse the design, stationary magnets and rotating windings connected to a brush commutator.
Please notice that a brushed motor has higher no-load currents due to the brush drag.
This slightly lowers efficiency. But you could improve this number by larger brush area at lower pressure.
Just reverse the design, stationary magnets and rotating windings connected to a brush commutator.
Please notice that a brushed motor has higher no-load currents due to the brush drag.
This slightly lowers efficiency. But you could improve this number by larger brush area at lower pressure.
major
10 kW
big said:
I think you will have difficulty with the physical commutator, both in the part (design/fabrication or purchase) and in the assembly (connection of your "cable bunch"). The commutator and brush gear design for 60 to 80 Amperes is not trivial.
major
10 kW
big said:
My point is: The commutator can be the determining factor in design criteria such as RPM, # of poles, # of coils, conductor size and shape, etc. These things will then influence the magnet and coil design. Also, examine the loss and cost associated with the commutator. I suspect for a one-off build or low volume production, the AC controller is the lower cost/higher efficiency choice.
major
10 kW
Honk said:
I agree that the OP appears to be mixing his fruit. But coreless BLDC would eliminate the steel in the stator which is the armature in that case. The magnets are placed on the rotor and can also have or not have steel which serves as backiron.
There are different reasons for going coreless. Cost is rarely a valid reason. In a moving coil motor, such as a commutator DC type, coreless can reduce rotor inertia and reduce core loss. In a BLDC, where the magnets are on the rotor, the core is the stator (stationary) and its elimination reduces (eliminates) core loss. In the BLDC, I don't think steel on the rotor would be considered "core" as the flux in it is basically unchanging.
At least that is my take on it. Furthermore, the OP looks for a 5 to 6kW motor, presumably for a vehicle propulsion. I wonder what value coreless really brings to the table. I believe some specific designs done for the solar racers were coreless to squeeze out a few tenths of a percent efficiency. But those came at a tremendous cost. The OP might search in that field to see what the design process entailed.
Honk
100 W
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In my bok a coreless design is eliminating the iron for the windings.
Perhaps I'm wrong but the idea of coreless is a lightweight rotor with low inertia.
When having a magnetic rotor it needs some backiron to enhance the flux strength
Magnets + backiron = high rotor inertia.
But using the windings as rotor doesn't require any backiron in a pancake motor = low rotor inertia.
Perhaps I'm wrong but the idea of coreless is a lightweight rotor with low inertia.
When having a magnetic rotor it needs some backiron to enhance the flux strength
Magnets + backiron = high rotor inertia.
But using the windings as rotor doesn't require any backiron in a pancake motor = low rotor inertia.
major
10 kW
Honk said:
Do you have, or know of, a BLDC with windings on the rotor?
parabellum
1 MW
Not totaly brushless, :lol: car generator.major said:
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