An analytical and experimental calculation of the inertia moment of a squirrel-cage induction motor

This paper presents a comprehensive analysis for the analytic and experimental calculation of the inertia moment of a squirrel-cage induction motor. The analytic calculation and a simplified proposed analytical approach are presented as an alternative for the attainment of the moment of inertia. Such methodologies have advantages, as they do not require the dismantlement of the motor neither the use of complex measurement instruments when compared with experimental approaches. The experimental setup is based on unifilar and bifilar torsion pendulums that allow the indirect calculation of the moment of inertia through the period measurement of the angular oscillations. To measure the angle, a measurement system was developed and it uses a quadrature encoder and a digital signal controller. The acquired angle waveforms are then used to estimate the oscillation frequency and the moment of inertia. Simple geometry flywheels are also used in the paper as an aid to verify the analytical results. A comparison of four different methods is carried out and it is concluded that both unifilar and bifilar pendulums give good experimental results. Finally, a simplified approach for attaining the inertial moment is presented and it offers a straightforward way of calculating it with acceptable accuracy.