Hello. I am found a 3 wire dc motor that is in brand new condition. I tried hooking it up with a dc power source its a dc motor. It has three wires and green black and red. the number ldc on my 36 volt power supply flickers so i think the power cables are not hooked up properly. I know what 3 phase ac motors are and how they work but i do not know much about a 3 wire dc motor. I read around and heard you need a micro controller to control a 3 wire dc motor. Does anyone know how to make a or get a simple controller for one of these motors or anything about them. Thanks.

If it is a BLDC (3 wire) then straight DC is not much good, Unless it has an internal controller, you would need to verify just what you have first before trying to control it.
If you did actually feed it straight DC then I assume you did not use the green wire, which in this case would probably be the GND, again verify resistance to frame.
Also if feeding it straight DC and and it ran and has NO brushes, then it smacks of an internal ECM motor of some kind.
Max.

 

Still, quite a few hours later, and after reviewing all of the comments, we have no response about if it ran when he connected the power. We have no idea if the TS has a meter or knows how to check resistance.
A brushless motor should give a twitch when some DC is applied to two terminals, but it will not run. If it runs then it either has internal electronics or it is not brushless.. We have no mention as to the size of the motor, either, or why the TS believes that it is a DC motor.

 

Yes and we likely never know. So it goes and as you have seen it happens all the time. Something about taking a horse to water ...

Ron

 

Yes and we likely never know. So it goes and as you have seen it happens all the time. Something about taking a horse to water ...

Ron

There is a funny story about that, relating to the Mounted Police in New Orleans. They tried to train the horses to only relieve themselves in specific locations, and they used beer as the reward for the horses doing as the trainers wanted. They thought that it should work but instead they just got a bunch of alcoholic horses.
From this we learn: You can drive a horse to drink, but you can't make him water.
I told you it was a funny story!!

 

A brushless motor should give a twitch when some DC is applied to two terminals,

Why do you think that? It would only happen IF the rotor and stator HAPPENED to be in the correct position for the two wires chosen. Don't even know how to predict the chances of it happening.

 

If you posted a picture of it we might be able to immediately say it's an RC brushless DC motor.

If so you can probably power it with this ESC (electronic speed controller) ("Probably" because it has to be rated for the amount of power used). You can drive the speed controller with an Arduino, or something even simpler.

 

Why do you think that? It would only happen IF the rotor and stator HAPPENED to be in the correct position for the two wires chosen. Don't even know how to predict the chances of it happening.

I know exactly how to predict those odds:
If the motor is a 3-phase type BLDC motor then at any time it is not centered on a specific position, and hence it would move a bit when momentarily energized. So the odds are two to one that it would twitch a bit. And if the experimenter turned it a bit after a first try the odds would be even better.

 

Now we have to clearly define "twitch" and convert twitch to degrees of rotation. At one time I did have a small little BLDC motor I took out of a disk drive, if I could find it in this pile of junk on the desk I could try for a twitch.

Ron

 

I have several BLDC servo's on hand left over from the Retro-fit days.
Even simpler, if it is truly a BLDC Without internal controller, shorting two leads in turn should indicate resistance when the shaft is spun for each pair.
If an internal controller is present, then obviously no difference.
Max..

 

Now we have to clearly define "twitch" and convert twitch to degrees of rotation. At one time I did have a small little BLDC motor I took out of a disk drive, if I could find it in this pile of junk on the desk I could try for a twitch.

Ron

A "twitch" is clearly defined as a small amount of motion. It would probably approach one pole spacing,

 

A "twitch" is clearly defined as a small amount of motion. It would probably approach one pole spacing,

Bill, it was an attempt at adding some humor. I know what a twitch is in the context you used it. Think humor here.

Ron

 

I know exactly how to predict those odds

Thought you might. But it's perfectly clear you don't understand how they work.

 

Thought you might. But it's perfectly clear you don't understand how they work.

They work in a manner similar to a synchronous three-phase motor.when a particular phase is powered the rotor poles are attracted . And that is what putting a bit of DC onto one phase would do. Not run it, just twitch it a bit. OF COURSE, this is presuming that the connection is directly to the coil set of one phase, and not to the electronic driver, which the TS has not mentioned having.

 

What ever you say. But your wrong. But the best way of telling if it is a BLDC motor is the one Max said.

 

What ever you say. But your wrong. But the best way of telling if it is a BLDC motor is the one Max said.

OK, now I re-read it and see that he means that "Shorting two leads will CREATE resistance TO TURNING." I had though that he was talking about OHMS resistance. That method can also work, but it is not the only way. So the method that I suggested may not be the simplest one.
Further, shorting the leads of a PMDC brushed motor will increase the resistance to tuning as well. In fact, shorting the leads of an induction motor that has any residual magnetism left will also increase the torque to turn it some.

 

They work in a manner similar to a synchronous three-phase motor.when a particular phase is powered the rotor poles are attracted . And that is what putting a bit of DC onto one phase would do.

BLDC and AC synchronous PM field motors are constructed almost identically, in fact either can be adapted to run either method. But are quite different in manner of control.
I have converted Fanuc AC servo's in the past by converting to BLDC.
The difference of course is that the AC version is fed with a true 3phase type power,
With BLDC, only two windings are energized at any one time. Representing a normal DC motor turned inside-out. Hence BLDC.
Max.