Also i think their Magnet to Pole(teeth) ratio are different.
I will make my first E-car using 3Phase Induction electromotor(like tesla model s)(not soon)

Hey!! I’m a little bit late haha, but I’m also interested in the idea of converting a three-phase AC motor to BLDC. I just want to ask: did you finish your project? Does the motor work? Does it fulfill your expectations? How efficient is it, and was it worth doing?

Mod: link to old thread,
https://forum.allaboutcircuits.com/...otor-to-bldc-or-pmdc-pmsm.159685/post-1397251

 

I just want to ask: did you finish your project? Does the motor work? Does it fulfill your expectations? How efficient is it, and was it worth doing?

The person you are asking was last seen on this forum in 2021.

 

For one, the typical BLDC motor has between 1 pair and 4 pair of Permanent magnet poles on the rotor.

 

IT should be possible to use a circuit of a three pahse output variable speed drive to produce a similar function to a BLDC motor and driver circuit. Certainly they are not at all the same. BUT many VS drives first rectify the mains power to DC, soit should be possible. NOTEthat I did not say it would be simple or easy.

 

The problems I see, is in providing, what is usually rare-earth magnets for the rotor poles and then getting them balanced !

 

BLDC = Brushless DC motor. These motors have magnets spinning around a fixed stator, almost always inside a cylindrical rotor, otherwise , the centerfuge force will send magnets flaying.

 

There's no such thing as a brushless DC motor. All DC motors have brushes. What the world likes to call a "brushless" DC motor is in fact an AC permanent magnet synchronous motor, driven by an inverter.
So do you want to convert the induction motor that you have to permanent magnet? That might be tricky, but you can run a 3-phase induction motor off an inverter, and it isn't quite so tricky as running a synchronous motor as you don't need to time the signals to match the position of the rotor.

 

There's no such thing as a brushless DC motor. All DC motors have brushes. What the world likes to call a "brushless" DC motor is in fact an AC permanent magnet synchronous motor, driven by an inverter.
So do you want to convert the induction motor that you have to permanent magnet? That might be tricky, but you can run a 3-phase induction motor off an inverter, and it isn't quite so tricky as running a synchronous motor as you don't need to time the signals to match the position of the rotor.

IF you include the driver as a part of the motor, THEN you can certainly have a "brushless package."AND THAT is what gets called a BLDCmotor. Many of them, maybe even most of them, also include rotor position sensors so that they always start out the same. So if you include the "package" that it must have to run, then there is such a beast as a brushless DCmotor. That may confuse some folks, no doubt.

 

There's no such thing as a brushless DC motor. All DC motors have brushes. What the world likes to call a "brushless" DC motor is in fact an AC permanent magnet synchronous motor, driven by an inverter.

I don't neccesari;ly agree there, the BLDC typically uses DC switching to one pair of the three windings at a time, the applied signals do not alternat or reverse polarity.Hence DC.
The identical motor can also be driven with 3 phase sinusoidal. making this version basically AC.

 

There's no such thing as a brushless DC motor. All DC motors have brushes. What the world likes to call a "brushless" DC motor is in fact an AC permanent magnet synchronous motor, driven by an inverter.
So do you want to convert the induction motor that you have to permanent magnet? That might be tricky, but you can run a 3-phase induction motor off an inverter, and it isn't quite so tricky as running a synchronous motor as you don't need to time the signals to match the position of the rotor.

Just takes a simple googling
Brushless DC electric motor - Wikipedia

 

I don't neccesari;ly agree there, the BLDC typically uses DC switching to one pair of the three windings at a time, the applied signals do not alternat or reverse polarity.Hence DC.
The identical motor can also be driven with 3 phase sinusoidal. making this version basically AC.

That's an interesting thought, though I will add one a couple of things:
Driving the motor with unipolar signals isn't an efficient use of the windings so it will probably only be done for low power motors.
If you drive on terminal with a unipolar signal, then the effect of the motor being a generator will put a voltage of the opposite polarity on that terminal when it is not driven, so a measurement of the voltage between the terminals would still give AC.
Very much the case of "depends how you look at it".

 

What I see here is an argument about exact definitions. This argument will produce nothing of value at all.
Therefore I suggest abandoning it and thus saving a bit of bandwidth.

 

What I see here is an argument about exact definitions.

That would be room twelve. !

 

That would be room twelve. !

Is it the 5 minute argument or the full half hour?

What I'd like to know from the TS, is whether he simply wants to make his motor rotate using a DC supply bu adding some electronics, or whether he wants to convert it to be a permanent magnet motor.

 

I stepped (or rather stumbled) into room 12 without paying that one L

 

I’m also interested in the idea of converting a three-phase AC motor to BLDC.

If typical induction motor, I would say not worth the work, results may not be very stellar !

 

An AC supply alternates in sinusoidal pattern, which is not used in a single BLDC on this earth.
" The usual waveform of alternating current in most electric power circuits is a sine wave, whose positive half-period corresponds with positive direction of the current and vice versa (the full period is called a cycle). "Alternating current" most commonly refers to power distribution, but a wide range of other applications are technically alternating current although it is less common to describe them by that term. " Wikipedia

 

An AC supply alternates in sinusoidal pattern, which is not used in a single BLDC on this earth.

Not so. if they want particularly smooth movement, they are sinewave driven.

 

" The usual waveform of alternating current in most electric power circuits is a sine wave,

Note the word "usual".
Doesn't say that they all are.

 

All that it takes to convert a three phase inducion motor into a brushless DC motor is a variable speed drive system that runs from a DC source. BUT usually these packages are separate, so it does not work out quite right. AND, most VS drive systems use an AC feed.