Hello, I have been thinking about building a big bldc motor like 20kw or so. I have been looking around on internet for information about the topic, I have just found people that build smaller motors or some that builds the size that I am looking for but just dont explain anything. I have all necessarily tools like laser cutter, lathe and so on. Any one how knows where I can studdy this topic or If there is some good tutorials. I need to know like how thick coper wire to use, how to wind and so on. Thankful for answer

 

Welcome to AAC!
That project would be a challenge even for experienced people. Why not build a smaller prototype first to gain experience in the technology involved?
How will you power this motor?

 

IMO Your biggest challenge is going to create the large magnets for the rotor!
Have you decided how many poles it will be?
That is almost 30HP! A really BIG motor!

 

Hello, I have been thinking about building a big bldc motor like 20kw or so.

When pickles fly.

 

The very first thing to do is to look at similar rated motors in some manufacturers catalog. Possibly go to a manufacturer's site and see details. AVOID ANYTHING SHOWN ON THE CARTOON CHANNEL, also called you tube.
There are also some motor manufacturers that sell frameless motors, which could provide you with the hard parts while you could create the frame that supports them.

 

Thevery first thing to do is to look at similar rated motors in some manufacturers catalog. .

30HP BLDC?
The drive will be quite impressive!

 

Certainly the drive will be quite impressive indeed. Of course, even for a common induction motor, 20KW/30 HP/480V/3Phase, the starter is big enough to stand out on the electrical controls panel.
What would such a motor be used for? An electric car, possibly??
Knowing the proposed applicationn will be interesting.

 

Locomotives now use large AC traction motors on each wheel set, but these are 3ph AC, Not BLDC.
The VFD drives use large IGBT.s , It may be more practical to use the same principle as it would be very much cheaper than a PM AC (BLDC) version.
Where the cost of rotor rare earth magnets would be prohibitive!

 

----> https://www.directindustry.com/industrial-manufacturer/electric-vehicle-wheel-motor-248293.html

----> https://ozo-electric.com/en/254-wheel-motors-3000w-to-15000w

Several flavors at ----> https://search.brave.com/images?q=wheelmotor for car

with intrusion of some toys...

 

According to that first link in post #9 .......


Methinks there's a typo in the power rating .

 

Certainly the stated power does not seem to match with the claimed performance. So where is this wheel hub drive motor claimed to be available??
OR, is this an over-unity efficiency claim?? OR the copy writer could not believe 7700 watts.

 

A tad more than 7700Watts. 650Nm x 1280rpm = 100.69kW (134.92HP) !!

 

OK, not a simple goof. More like a blatant lie.

 

1st and main! To build a 20 kW motor by own hands will cost roughly 1000x expensiver as to buy a scratched motor at the second hand market.
2nd - the wire diameter is calculaded using the 3.5 A /mm2 except the sharp wind conditions when may risk to think about 5...7 A/mm2.
3-rd - the magnetic circuit cross section is assumed using the rough calculation each cm2 gives about 1 kg of force. And each 50 cm2 demands a 1 turn per Volt at standard 380 V 50 Hz mains
4-th - the rpm are depending on bobbins connection scheme, two-poles or less or more. Thus 3000 rpm, 1500, 100, 750 rpm etc.

 

What would the motor you build be used for after it is completed? Certainly it will be enough effort to make that there must be an intended application for the motor. Also, what about the driver portion of the system? A 20kW motor will require a 20 kW driver, which is not a small project. AND, what voltage will this motor driver be supplied with?? 20kW output means more than a 20 kW supply input, not typical household wiring.