How is the required torque calculated?
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The torque characteristics of the stepper motor show the dynamic torque against the speed or step frequency. Among other things, the dynamic characteristics of the stepper motors also depend on factors such as the type of power drive and the level of the supply voltage.
In addition, the moments of friction and moments of inertia as well as the section modulus and, above all, also the acceleration torque must be taken into account when designing and dimensioning the stepper motors.
a) Friction (adhesion and rolling friction) This is a torque that counters the rotation of the motor. This torque can be schematized best with the balancing weight system or the adhesion and rolling friction system.
b) Load inertia moment (also rotor inertia) This occurs at positive or negative acceleration. In the case of short accelerations and delays, it is imperative that the corresponding acceleration torques or delay torques are taken into account and must lie below the torque curve.
c) Section modulus is created when the a) and b) torques are countered by a 3rd force or torque. It occurs as dry friction during normal machining (metal machining such as milling, drilling, lever etc.) or as liquid or air friction and then also acts proportional to the speed.
d) Simple torque determination In addition to mathematical determination, primarily the force and torque determination is advantageous with spring balance and torque gage because the difficult-to-determine friction factor is taken into account.
e) Power determination If you already have a motor and only have its rating table (e.g. 50 W), the following formula can be used for the calculation: Md = P/(n * ˜0.1); (n= speed in rpm, Md= torque in Nm). Alternatively, the following applies: Md= P * z / 6.28 * f; (P = power in W, z = steps/revolution, f = frequency in Hz)
