how to calculation stepper moment force stepper motor , also power question

Projects General Guidance
1

hello,
i have nema23 and i have to calculation the moment force of the stepper motor
i set the rpm to 70rpm
Holding Torque is 20kgcm
i use 24v

  1. how can i calculation the moment force ?

  2. how can i calculation the power of the motor?

2

I reckon the simplest way is to look up the graphs of torque vs speed on the manufacturer's datasheet.

If by "power of the motor" you mean the mechanical power it can impart to something else then you need to know the torque and the speed.

...R

3

i need in theory to know for the first choosing of motor

i mean if i use some of ohm rule
to know the P
P=v^2 / R
that is right to go from here?

4

yoyobazoka:
i need in theory to know for the first choosing of motor

With respect, that does not make sense.

if you have not chosen a motor then you need to calculate or measure the torque that your project requires. When you know that you can then look at the manufacturer's datasheets to identify a suitable motor.

Calculating the output power for a stepper motor from its voltage and current is impractical because they draw much the same current all the time, even when stationary. The fall-off in net torque as speed increases is affected by complex factors including inductance and impedance - hence the need to refer to the datasheet.

...R
Stepper Motor Basics

5

I would assume in the "real world" where you are driving some sort of mechanism it's almost impossible to make an accurate calculation. In the real-world, you're rarely just turning a flywheel or lifting a constant weight or anything that's simple to calculate.

You might be able to calculate an approximate value, but I think you'd have to measure the required torque (which may not be easy either, especially if you don't have some kind of motor) or make a guess/estimate and then try just it.

You may be able to calculate the amount of work/energy for whatever you are ultimately moving, and then throw-in an allowance for inefficiency/loss in your mechanism/gearing/pulleys/whatever. Steppers are less forgiving than most motors because you can loose a step or slip a step without knowing it. So, you've probably got to over-design.

6

Overview of force and torque