BLDC motor - physical quantites

[nForce]

Why does B (magnetic density) change like a square function in BLDC motor? And why does magnetic flux change like a ramp function, it goes up and then down and again up...?
Why is B the derivative of magnetic flux, and where does magnetic field induce emf?

Thanks.

[nForce]

So no one knows what is the function of magnetic density (B) and magnetic flux in BLDC motor?

[T3sl4co1l]

Square function of what?

Flux a ramp function of what?

What is the definition of B, anyway?

I suspect, if you took a little more time to prepare your questions, you will find your answer in the process!

It is a very useful technique.  I've answered many of my own questions this way.  All too often, answering them myself after hitting "Post" and only then thinking about what was missing... but my rate seems to be improving over time.

Tim

[mac.6]

It's a whole field of physics: electromagnetism

[ace1903]

One experiment is worth whole book of theory.
Make an experiment with real BLDC motor. Connect scope on one of the coil and turn rotor by hand drill.
You will see induced emf in the coil and its form.

Most book authors do copy paste from other books and forget to explain that ramp function is like design goal when designing BLDC motor.
It is also simplification when doing mathematical model of BLDC motor.

In practice ramp function it is impossible to get with normal shape of the magnet and iron pole.
Many motors that I have used have sinusoidal form of induced EMF and technically they are same as pmsm motor.