How to find best motor for wind turbine generator ?

Thread Starter

pripyat.tech

Joined Apr 21, 2021
7
How to find best motor for wind turbine generator ?
Is 3500 RPM 3HP DC motor is good for this ?
How to find motor with good efficiency ?
 

BobTPH

Joined Jun 5, 2013
3,794
Sorry, but needed information is definitely lacking. You might be talking about a 20KW system or 10W for all we know. Need to know, at least, how much power you expecting to generate and what RPM and torque the windmill provides. Probably much more.

Bob
 

Thread Starter

pripyat.tech

Joined Apr 21, 2021
7
Sorry, but needed information is definitely lacking. You might be talking about a 20KW system or 10W for all we know. Need to know, at least, how much power you expecting to generate and what RPM and torque the windmill provides. Probably much more.

Bob
It's only about 2KW range
 

Papabravo

Joined Feb 24, 2006
16,961
For any particular set of requirements, the short answer is that you design and build the motor that you need. Any off the shelf motor that you can buy was designed for somebody else's needs and requirements. Are they close enough to your needs and requirements? Only you can tell.
 

Thread Starter

pripyat.tech

Joined Apr 21, 2021
7
For any particular set of requirements, the short answer is that you design and build the motor that you need. Any off the shelf motor that you can buy was designed for somebody else's needs and requirements. Are they close enough to your needs and requirements? Only you can tell.
Can you help ? I am new in generator making.... is higher voltage-rpm ratio is better ?
I am expected to have DC output
If DC motor is 3HP 220v DC with 1500rpm, if motor speed is about 150 rpm is that mean that motor generate 22v DC output ?, it's my understanding true ?
 

Papabravo

Joined Feb 24, 2006
16,961
Better for what?

Do you know if the motor has a linear relationship between RPM and voltage output?
Do you know if the power output is the same at 1500 RPM and 150 RPM?

You make a number of assumptions, but you seem confused about whether they are true or not. To be fair, I'm a bit rusty on my motor technology so I'm probably not going to be much help. What I do remember is:
  1. More current implies more torque
  2. More speed implies less torque
  3. Low speed implies low back EMF
  4. High speed implies higher back EMF
I would add to that, never assume a linear relationship unless you can verify it over the range of interest.
 

Alec_t

Joined Sep 17, 2013
12,249
is higher voltage-rpm ratio is better ?
Are you aiming simply to generate as high a voltage as possible? Or do you want a regulated voltage output (e.g 24/100/250V) with as high as possible output current capability? If the latter, what voltage? It may be that a standard alternator would meet your needs.
 

wayneh

Joined Sep 9, 2010
17,153
Can you help ? I am new in generator making.... is higher voltage-rpm ratio is better ?
In general, no. Most motors repurposed as generators will be not be ideal. They usually have too many turns of finer wire than desired. They'll make plenty of voltage if spun fast enough but not as much power as they would be capable of with less turns of heavier gauge winding.

Optimizing the power production by a windmill is extraordinarily difficult. All systems interact and you cannot optimize them separately.

The biggest challenge is the physical fact that the available power from wind varies with the cube of the windspeed. You might design a mill to optimally capture energy on the 3 days of the year you have 50mph winds. This would capture a large fraction of what is available throughout the year. But it would also be suboptimal most of the year. Conversely you could optimize your mill for 10mph and this would do a better job on most days. But you'd have to shut it down on the high wind days because a design that's optimal at 10mph can't possibly be expected to function when the input power is 3 orders of magnitude higher.

What to do? Rely on the experience of others and accept that "good enough" is the best you can expect on a DIY project. Find and follow a proven design.
 

Papabravo

Joined Feb 24, 2006
16,961
In general, no. Most motors repurposed as generators will be not be ideal. They usually have too many turns of finer wire than desired. They'll make plenty of voltage if spun fast enough but not as much power as they would be capable of with less turns of heavier gauge winding.

Optimizing the power production by a windmill is extraordinarily difficult. All systems interact and you cannot optimize them separately.

The biggest challenge is the physical fact that the available power from wind varies with the cube of the windspeed. You might design a mill to optimally capture energy on the 3 days of the year you have 50mph winds. This would capture a large fraction of what is available throughout the year. But it would also be suboptimal most of the year. Conversely you could optimize your mill for 10mph and this would do a better job on most days. But you'd have to shut it down on the high wind days because a design that's optimal at 10mph can't possibly be expected to function when the input power is 3 orders of magnitude higher.

What to do? Rely on the experience of others and accept that "good enough" is the best you can expect on a DIY project. Find and follow a proven design.
Thank you for that. I knew intuitively from what I know about motors that an optimal solution was not readily available, but I could not articulate it clearly. You have done the TS a considerable service.
 
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