Motor Choice

Thread Starter

Accelerate F=ma

Joined Aug 6, 2018
11
Could I get your advice about my choice of motor.
I would like to use a motor to generate electricity when being turned passively and charge batteries like a wind generator. When the wind speed drops below a set point I want to activate the motor to maintain minimum RPM on the fan to function like a cruise control for the wind. I'll use an Arduino with a rotary encoder to measure RPM, control the motor and charging.

Design goals are to generate up to 2A @ 5000RPM for charging batteries, Then be able to run at up to 5000RPM by the motor. The motor should be small, lightweight and inexpensive.
Ideal shape would be flat like a pancake and have low drag when being turned passively. Possibly frame-less.
What motor do you think would work best in this situation?

Thank you, I appreciate your advice

-Chris
 

MaxHeadRoom

Joined Jul 18, 2013
19,671
You didn't mention voltage?
Just about all P.M. motor will generate, from small DC, BLDC, RC motors, rotation resistance will increase with generated current.
Max.
 

kubeek

Joined Sep 20, 2005
5,656
...to maintain minimum RPM on the fan to function like a cruise control for the wind.
could you explain this a bit more?
Anyway, I think some small BLDC motor for RC stuff could solve the low drag and small size. But it is harder to drive than a normal dc motor, but I really doubt what that would achieve.
 

Bernard

Joined Aug 7, 2008
5,351
I'm still confused, two motors, one used as a wind generator & one used to run generator when wind is low.
What is power source for the second motor ? I hope it isn't the generator = a no no here.
 

Yaakov

Joined Jan 27, 2019
1,612
Your requirements are probably unreasonable.

For example, this one, which seems pretty shady, doesn't even claim such capacity.
(If you look at the last photo, it seems quite fake.)

You'll probably have to compromise on some part of small, cheap, fast because you probably aren't get all three.
 

Thread Starter

Accelerate F=ma

Joined Aug 6, 2018
11
I would like to create a constant flow of air.
When air speed is below minimum the motor will push it faster.
When the air speed is above the minimum it will charge batteries.
Will be using one motor.
Possibly a frameless BLDC if I can figure out how to make a regenerative driver for low cost.
Brushed DC could be an easier style to integrate while creating both the drive and charge functions with minimal expense.
 

Yaakov

Joined Jan 27, 2019
1,612
I'm still confused, two motors, one used as a wind generator & one used to run generator when wind is low.
What is power source for the second motor ? I hope it isn't the generator = a no no here.
What I understand is the motor will spin with the wind and generate power until the wind calms and it will proportionally be powered to maintain the 5000RPM spin. So, one motor.
 

kubeek

Joined Sep 20, 2005
5,656
AFAIK if you set the PWM of a motor to be constant with a bldc driver, then when the motor is overpowered by wind, the voltage automatically gets fed back into the supply of the driver, it works as a two quadrant step down - stepping down in one direction, stepping with the same ratio up in the other direction of current.
You will however need to be able to use that energy coming from the fan somehow in all cases, otherwise the rail voltage will go up and you will likely fry something in the process, so a backup brake resistor is a good thing to have in the system.
 

kubeek

Joined Sep 20, 2005
5,656
I personally would go with one of those that have available firmware and sourcecode/mod, just to be sure you can use it as you wish.
I don´t know any brands, just have some idea what exists on the market through some friends.

I have a feeling that anything that does the pwm based on your input will work ok. On monday I could ask someone who was doing a testbench with two motors connected together and playing with regenerative braking.
 

mvas

Joined Jun 19, 2017
538
Could I get your advice about my choice of motor.
I would like to use a motor to generate electricity when being turned passively and charge batteries like a wind generator. When the wind speed drops below a set point I want to activate the motor to maintain minimum RPM on the fan to function like a cruise control for the wind. I'll use an Arduino with a rotary encoder to measure RPM, control the motor and charging.

Design goals are to generate up to 2A @ 5000RPM for charging batteries, Then be able to run at up to 5000RPM by the motor. The motor should be small, lightweight and inexpensive.
Ideal shape would be flat like a pancake and have low drag when being turned passively. Possibly frame-less.
What motor do you think would work best in this situation?
Thank you, I appreciate your advice
-Chris
You must specify the details of the Blades of the Wind Turbine:
a) Type / Style
b) # of Blades
c) Diameter of the Rotor
d) Pitch of the Blades
e) TSR
f) Shaft RPM vs Wind MPH
etc, etc, etc

Also, what is the minimum, average and maximum Wind Speed?
So that you can select the appropriately sized Motor / Generator.

2 Amps at 5 Volts will charge WHAT battery bank?

Using gears to spin a motor at 5,000 RPM from a slow turning "Small Wind Turbine" shaft, is not typical, and may not be reasonable.

So, you want to maintain a constant wind speed ?
But you did not specify the MPH or volume per minute of this constant wind speed.

We need way more details ...
 
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Thread Starter

Accelerate F=ma

Joined Aug 6, 2018
11
I used an analogy of wind flow as a simple hypothetical situation that would describe a need that is functionally the same but I'm not actually working with air or wind. I'm using a Gyroscope rotor to create angular momentum to be the catalyst of a reaction in a physics engine.
 

Alec_t

Joined Sep 17, 2013
10,690
I don't get the analogy.
According to Wikipedia :-
"A physics engine is computer software that provides an approximate simulation of certain physical systems".
Can't you just simulate a motor?
 

Yaakov

Joined Jan 27, 2019
1,612
I used an analogy of wind flow as a simple hypothetical situation that would describe a need that is functionally the same but I'm not actually working with air or wind. I'm using a Gyroscope rotor to create angular momentum to be the catalyst of a reaction in a physics engine.
I'm sorry but why would you do such a thing?

Please, in the future, present the real problem—not something you imagine is "simpler" and equivalent. If you need help, why would you imagine your "simplified" case would be relevant or appropriate? Tell the truth, that is, explain what you are actually trying to do. It's the least you can do if you are asking for free help.
 
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