Calculating the strength needed for each electromagnet in a stepper motor

[SMD1990]

I am designing a stepper motor, and I need someone to check my calculations. The results seem impossibly low...

Suppose the vehicle driven by the motor is already up to speed. The force needed to maintain that speed are, say, 100 Newtons.

At the speed, the stepper motor performs 15,000 steps per second. Each step is a millimeter.

If a Newton = Kilograms * Meters / Seconds², then plugging in my values, I get:

100 Newtons = ? * 0.001 / 0.00006666²
100 Newtons = ? * 225000​

So, according to my calculations, each electromagnet would only need to be able to pull 0.444 grams from a millimeter away.

That cannot be right, can it? If so, the power needed to drive such a motor seems to be unbelievably low. I mean, even the smallest, weakest electromagnets I have ever made can provide that little of a pull.

Certainly, I must be in err? No?

 

[Vailanor]

No, your calculations seem to be correct. However, the force required to maintain a certain speed will vary depending on the inertia of the motor and the load it is driving. If the motor has a high inertia, or if the load it is driving is heavy, then the force required to maintain the same speed will be higher than the 100 Newtons you calculated.