# How to make BLDC motor of 125 torque?

If I want to make a BLDC motor such that it operates at 48V, 60 rpm and can achieve 125 Nm of torque, for such an engine, which is need relationship slots/magnetic poles required, the length L and the coil parameters required (formulas)?

Thanks.

Are you joking?

To start with more information is needed such as the gear ration. How are you going to control it, that has a big effect on torque. I would suggest you you get a few books on motor design. When you have finished that you will understand why we do not want to write a book to answer your question.

How are you going to control it, that has a big effect on torque.

I would control using a controller board with RTOS and sensors.

Aleksandari:
If I want to make a BLDC motor such that it operates at 48V, 60 rpm and can achieve 125 Nm of torque, for such an engine, which is need relationship slots/magnetic poles required, the length L and the coil parameters required (formulas)?

Thanks.

60 rpm is about 6 rad/s, so the mechanical power required is 6 x 125 = 750 watts.

power = angular velocity x torque

So you need a motor capable of this power, and suitable gearing to reduce its speed down to 60 rpm.

slots and poles count is irrelevant, so long as you get the gear ratio to match the actual motor, and the motor windings to match the supply voltage.

... and the motor windings to match the supply voltage.

??
It can a little more details?

slots and poles count is irrelevant, so long as you get the gear ratio to match the actual motor

Yes, but there must be a rule for how best to arrange slots and magnets?

If it not matter much, then how is best to collocate?
What is the advantage of one schedule over another?

Aleksandari:
Yes, but there must be a rule for how best to arrange slots and magnets?

To a first approximation all DC motors perform similarly, you are worrying about optimizations that
would take detailed mathematical modelling or multiple prototypes to compare. In general for a low
speed output shaft you'd favour a lower rpm motor (so the gearing is simpler), but there are tradeoffs
with power density, as slower = less power density (all else being equal).

If it not matter much, then how is best to collocate?
What is the advantage of one schedule over another?

You'll find some good online guides out there from people who've build and experimented with many
motor designs.