The project seeks to investigate large and small electric motors used mainly in home appliances and perform energy and thermal analysis of those machines. The main specific objective, from a technology point of view, is to develop computational tools capable of investigating local thermal effects, as well as those from transient operation of an electric motor. These models will allow the creation of "virtual thermal prototypes" of motors reproducing adequately the interaction between thermal and electrical parameters.
These developed models are intended to be used as part of an integrated analysis. Specifically, they have been designed such that predicts the distribution of losses within the motor. These losses are introduced into a thermal model, which is then used to calculate the temperature at different locations within the machine. The temperature outputs from the thermal model are then used as input parameters for the electrical model (affecting the resistance of stator and rotor) and the new motor loss can then be recalculated.
The thermal model consists of a thermal equivalent circuit, which involves the combination of global and distributed thermal parameters in different parts of the machine. These parameters are obtained from geometric data, material and fluid flow information, such as capacitance and thermal conductivities, heat transfer coefficients; in addition, it’s very important to understand the distribution of internal losses (heat sources) involved in the machine.
The purpose of the electrical model is to predict the motor electromagnetic response, as for instance torque, currents, rotational speed and losses generation as a function of applied voltage and load conditions. In the electrical model, the machine dynamics is described by a set of nonlinear differential equations. In order to obtain the dynamic characteristics, it is necessary to couple the electromagnetic torque with motor rotational speed, so that the produced electromagnetic torque is sufficient to overcome the resistive torque imposed by the system inertia and losses (ex. Drag and friction)
Therefore, the thermal and electrical behavior of the motor is the result of a complex and interconnected phenomena. Modelica language has been used as a solution methodology to solve this transient multidisciplinary problem; it is an object-oriented physical model language that allows modeling of mechanical, electrical, thermal, controls and other systems. The use of Modelica language for modeling thermal systems is something new in the work carried out POLO. In addition, from an academic point of view, this form of modeling is a great learning tool and transmission of knowledge about the proposed problem.