Resistive Loss Modelling for Inverter-fed Induction Motors

Abstract

The aim of this research is to model resistive losses in induction motors. The resistive losses in the form-wound stator windings of induction motors were modelled by using time-discretized finite element analysis (FEA) and circuit models. Loss modelling with a high level of accuracy by means of FEA can be used in the demanding design of electrical machines, typically for high-power and high-speed induction motors in spite of its high computational cost. Alternatively, the equivalent circuits served as a cheap computational tool for the rapid estimation of the resistive losses of 37-kW and 1250-kW machines for motor drives without using the machine data, typically the machine structure and materials. Electromagnetic losses lead to a temperature rise in electrical machines. As a result, temperature rise analysis is required to check whether the induction motors that are designed fulfill the IEC standard or design constraints. Thermal analysis employs FEA or a thermal network depending on the specific problems being studied. In this study, Finite Element Method Magnetics - a public domain code - was used to analyse the temperature rise of the form-wound stator windings of a 1250-kW induction motor. The thermal network was used in the thermal analysis of a 300-kW high-speed motor using form-wound stator windings. After the loss and thermal information have been collected, the losses in the stator form-wound windings of the induction motors are minimized in collaboration with temperature rise checking in the design stage. In addition, the loss and temperature rise analysis may offer numerical data to evaluate the possibility of using the form-wound windings for high-speed induction motors.