Experiments to observe the impact of power quality and voltage-source inverters on the temperature of three-phase cage induction motors using an infra-red camera

Nowadays, voltage-source inverters (VSIs) are widely used to control speed, torque and/or position of three-phase, squirrel-cage, induction motors (IMs). However, the harmonic distortion inherent to the VSI output PWM voltages leads to the increase of the motor operating temperature and, consequently, to the reduction of the electric insulation system lifetime. Additionally, the most common long-duration voltage anomalies in the power network, such as voltage magnitude deviation, unbalance and harmonic distortion, have a well-known impact on IMs´ performance and lifetime. The operating temperature increase due to poor power quality is particularly critical in the totally-enclosed, fan-cooled IMs. In order to allow a direct observation of the temperature distribution in IMs subjected to different voltage supply conditions, a set of experiments are proposed, using a totally-enclosed, fan-cooled IM, an end-shield-less, fan-less IM, and an infra-red camera to acquire the temperature maps in the frame for the first mentioned motor and in the stator core, stator windings and rotor for the last mentioned motor. The motor steady-state temperature is directly related with the losses being produced in it under different operating conditions, including ambient temperature, load, speed and input power quality. The proposed laboratorial experiments can be used to easily observe and study that relation, including the impact of PWM voltage supply and of individual voltage harmonics in the IMs´ operation, being a contribution in the scope of electrical engineering education, particularly for electric machines and power electronics courses.