Power, torque and speed

Choose a method

Find the torqueFor when the rated output and the speed of the motor are known. It finds the torque at the shaft.Find the powerFor when the required torque and speed are already fixed. It finds the power the motor has to deliver.Find the rotational speedFor when the power and the required torque are already fixed. It finds the speed that can be driven.

Formulas

Power P [W], torque T [N･m] and angular velocity ω [rad/s] are related by P = T ω. If the speed is given as N [min^-1] (rpm), convert it with ω = 2πN/60. That single equation ties all three together, so entering any two fixes the third.

Why 9550 is not used

The familiar T [N･m] = 9550 × P [kW] / N [min^-1] is the same equation rewritten for kW and min^-1. The exact coefficient is 60000/(2π) = 9549.2966…; 9550 is that figure rounded at the third digit.

Using the rounded 9550 gives an answer about 0.0074 % high. That is nothing in practice, but once the equation on screen disagrees with the implementation, you end up hunting for why the numbers disagree. So this tool holds no rounded constant: it converts ω to rad/s and evaluates P = T ω directly. A small difference from a hand calculation with 9550 is not an error.