How to find a motor to couple with another BLDC motor for testing?

Thread Starter

suji_03

Joined Jan 3, 2024
5
I am working on a project which needs to control a motor (3phase induction or BLDC), RPM ranging from 240 to 1600. Which I should be able to adjust either with ESC or VFD.
I will be coupling this motor to another BLDC motor which is part of a small wind turbine. Here I need to test the circuit board with wind simulating, The motor on the wind turbine is custom motor with limited information: Internal resistance of 11.3 ohms and 24RPM per Volt.
I am bit confused with which motor would be adequate for this project as for the motor to run at such a slow RPM.
I tested with single phase motor which was a drill, but it stalls at lower RPM
 

MaxHeadRoom

Joined Jul 18, 2013
28,692
A 3ph motor with VFD could do it down to very low RPM.
Most VFD's up to around 5HP can be operated on 1ph supply with 3ph out..
 

MisterBill2

Joined Jan 23, 2018
18,538
Probably the device on the wind turbine is either a generator or an alternator, It just looks like a motor. If the device is 24 RPM per volt,, and you spin it at 500 RPM you should get about 20 volts out. 24 RPM would give you one volt out, not worth the effort.

Keep in mind that the "24 RPM per volt" is just the speed/voltage factor, not a specification to run it.
Mostly a wind turbine is used to generate electrical power, so it seems like there should be some indication of what voltage is intended to be produced.
 

MisterBill2

Joined Jan 23, 2018
18,538
What we have here is a lack of clarity. Is the wind turbine being driven by a motor, OR is that custom motor used as an alternator?? what circuit board is being tested to do what??With wind simulation?? Missing information as to the whole context.
 

MaxHeadRoom

Joined Jul 18, 2013
28,692
What we have here is a lack of clarity. Is the wind turbine being driven by a motor, OR is that custom motor used as an alternator?? what circuit board is being tested to do what??With wind simulation?? Missing information as to the whole context.
It appeared to me that the OP wants to drive a BLDC motor using it for a wind generator, and needs a variable speed source to back-drive it for testing output.
As he says, "Wind Simulation". and the title:-
How to find a motor to couple with another BLDC motor for testing?
 

Reloadron

Joined Jan 15, 2015
7,519
24RPM per Volt.
Most wind turbines have a gear multiplier and most output DC to an inverter. While I doubt you have a 2.5 MW wind turbine this will give you an idea of just how slow they actually turn.

How big are the blades? Features 3 blades:

  • Each blade is about 164 feet long from center of hub to tip of blade
  • Weighs over 24,000 lbs each
  • Blade Rotation: Clockwise
  • Blade swept area: 84,000 sq feet (almost 1.5 times larger then the area of a football field)
  • Blade Orientation: Upwind
How fast can the blades travel? Blade tip speed is 165 mph at a hub rotation of 14.1 rpm

Granted this example is a massive monster wind turbine but note blade length verse tip speed on any turbine like this. They turn slowly.

I am bit confused with which motor would be adequate for this project as for the motor to run at such a slow RPM.
I tested with single phase motor which was a drill, but it stalls at lower RPM
So all you want to do is spin a small generator or alternator with a motor? You need to be specific in your goals ao those reading this thread wi9ll understand your project and objectives. Keep in mind that whatever you spin with needs to be capable of the force and torque required so less knowing the power out of whatever you spen suggesting a motor is impossible.

Ron
 

Thread Starter

suji_03

Joined Jan 3, 2024
5
Is the 24RPM/volt after 3ph rectification of the BLDC?
Also I assume you are running the back fed BLDC generator off load?
Yes the 24RPM/volt is after 3ph rectification.
Yes it is off load
I think 3 phase induction motor would be a good idea for low RPM with a VFD.
I will look into it
Thanks
 

MisterBill2

Joined Jan 23, 2018
18,538
The TS mentions two "motors. but 24 RPM per volt seems a lot more like a generator spec than a motor specification. And spinning a prop to simulate a wind driving a generator would be a reasonable check. But now I am wondering if this is for a display and the motor is simulating in pace of the wind spinning the prop.
But like so many posts, we are only given information about what the TS thinks is the big problem, and we are asked to solve the wrong problem without adequate information.
 

Reloadron

Joined Jan 15, 2015
7,519
The TS mentions two "motors. but 24 RPM per volt seems a lot more like a generator spec than a motor specification. And spinning a prop to simulate a wind driving a generator would be a reasonable check. But now I am wondering if this is for a display and the motor is simulating in pace of the wind spinning the prop.
But like so many posts, we are only given information about what the TS thinks is the big problem, and we are asked to solve the wrong problem without adequate information.
I have no idea but I ask questions and if the thread starter doesn't answer them I just move along. Simple little nit picky things like what the generator actually outputs for voltage and current so we get a clue what type motor would be suitable to drive it.

I want to build a matter transfer device to beam an ex wife to the center of a brick wall. Do I need a motor and how many horsepower should it be?

I am done here since the TS can't provide any useable information.

Ron
 

Thread Starter

suji_03

Joined Jan 3, 2024
5
The TS mentions two "motors. but 24 RPM per volt seems a lot more like a generator spec than a motor specification. And spinning a prop to simulate a wind driving a generator would be a reasonable check. But now I am wondering if this is for a display and the motor is simulating in pace of the wind spinning the prop.
But like so many posts, we are only given information about what the TS thinks is the big problem, and we are asked to solve the wrong problem without adequate information.
What I am trying to achieve here is testing a wind turbine, which is very small, it charges an internal battery of 12000mAh.
I have some test points on the circuit board which need to be tested for appropriate voltages when the turbine spins.
Since I dont want to take it outside and test it in real world, I want to couple it with another motor and spin it at different RPMs
 

MaxHeadRoom

Joined Jul 18, 2013
28,692
What I am trying to achieve here is testing a wind turbine, which is very small, it charges an internal battery of 12000mAh.
Since I dont want to take it outside and test it in real world, I want to couple it with another motor and spin it at different RPMs
That was the impression I got from the post!
 

MisterBill2

Joined Jan 23, 2018
18,538
Not the impression that I got, but then I think differently than a lot of folks. Now it makes sense, sort of. Spinning a generator with a motor also makes sens. So the one device, I am guessing, is that device rated at 1 volt per 24 RPM. So evidently it is a low power generator system. It seems reasonable then that the other motor should be able to spin it, although we do not know the actual power that the generator will deliver. WE can guess that with a resistance of 11 ohms and a low voltage output that it is not a lot.
 
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