Calculation of Machine Motor Power with High Inertia Masses and the Small Moments of Static Resistance

Abstract

To determine the motor power required for providing the specified machine acceleration there is a need to know the relative start time. The known formulas are obtained by numerical integration of the starting characteristics of motors provided that the acceleration process ends when the motor accelerates to nominal speed. In real terms the acceleration process ends when the rotor speed corresponds to the static moment of friction forces.

This paper provides numerical integration of the starting characteristics of asynchronous motors with the cage and wound rotor and presents curves of calculated relative start time, taking into account the static load.

When calculating the required power of the motor, which runs in the mode of frequent starts and stops in the mechanisms that have high inertia loads and small moments of static resistance it is possible to use the motors of lower power and lower the dynamic loads at start-up a by virtue of a small increase in start-up time calculated by the above formulas. It is shown that the three-stage rheostat start-up of slip-ring motors is more preferable than the two-stage startup.