Copyright © Oti Stephen Ejiofor et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. International Journal of Engineering &Technology, 8 (4) (2019) 500-508 International Journal of Engineering & Technology Website: www.sciencepubco.com/index.php/IJET Research paper Development and thermal modeling of an induction machine Oti Stephen Ejiofor 1 , Ugwu Justin 1 , Nnadi Damian Benneth 1* , Ogbuefi Uche 1 1 Department of Electrical Engineering, University of Nigeria, Nsukka, Enugu State. Nigeria *Corresponding author E-mail: damian.nnadi@unn.edu.ng Abstract In induction machines, the major concern is the temperature rise since it determines the maximum loading, in an attempt to avoid insula- tion deterioration and eventual loss of motor life. The effect of excessive heat in the motor stator and rotor windings and the stator mag- netic circuit can degrade the developed performance of the machine and also affect the motor loading and life span if not dispensed properly. This research work examines the thermal model for estimating the stator and rotor temperatures in cage induction motor. A state-variable model of the induction is used. The twin-axis stator reference frame is used to model the motor’s electrical behavior, be- cause physical measurements are made in this reference frame. The thermal model is derived by considering the power dissipation, heat transfer and rate of temperature rise in the stator and rotor. The non-linear equations for electrical behavior of the motor and the thermal state equations for the stator and the rotor are solved using the MATLAB/Simulink blocks. This is to give room for the determination of the temperature of the stator and rotor windings inside the induction machine so as to evaluate the thermal stability of the induction mo- tor and to check whether the insulation of the copper windings is sufficient at different operating conditions. It was found out from the thermal model analysis that the temperature of the stator and rotor windings increases due to stator and rotor copper losses which depend on the stator current. As the stator current is increased by increasing the torque, the temperature of each element is consequentially made to increase. Keywords: Induction Motor; Thermal Analysis; Modeling; MATLAB Simulation; Temperature. 1. Introduction The advent and successful take off of the transformer gave rise to serious research in the area of alternating current generation, transmis- sion and distribution. The power system industry, witnessed a speedy growth with the presence of the AC machine; Synchronous and Induction Machines. Induction motors are the most common motors used in industrial motion control systems, as well as in main pow- ered home appliances. Simple and rugged design, low-cost, low maintenance and direct connection to an AC power sources are the main advantages of induction motors [1]. Various types of induction motors are available in the market. Different motors are suitable for dif- ferent applications. Although induction motors are easier to design than DC motors, the speed and the torque control in various types of induction motors require a greater understanding of the design and the characteristics of these motors. Three-phase induction motors are widely used in industrial and commercial applications. They are classified either as squirrel cage or wound-rotor motors [2]. These mo- tors are self-starting and use no capacitor, starting winding, centrifugal switch or other starting devices. They produce medium to high degrees of starting torque. The power capabilities and efficiency in these motors range from medium to high compared to their single- phase counterparts. Popular applications include grinders, lathes, drill presses, pumps, compressors, conveyors, also printing equipment, farm equipment, electronic cooling and other mechanical duty applications. Due to the growing need of induction motors in the industrial sector, there is a growing emphasis on an acceptable and adequate analysis and modelling methodology of this type of Electrical Machine for all modes of operation. Problems concerning stability of power systems, computer-aided simulation techniques are commonly used. In recent years, [3] shows that, significant improvements have been obtained in the area of power system simulation; in particular, atten- tion has been given to the statement of the mathematical problem suitable for computer implementation, as well as to the modeling and identification, of the single components of a system (generators and motors). Nevertheless, no common agreement has been reached on the fact that known procedure can achieve a degree of accuracy adequate for new requirements. The Induction Machine is constructively, composed of a stationary member called the stator where the armature winding is located and a rotating member called the rotor where the field winding is located. One basic and distinguishing feature of the induction machine is that it is a singly excited machine. Although such machines are equipped with both field and armature winding, in normal use an energy source is connected to one winding alone, the field winding. Currents are made to flow in the armature winding by induction, which cre- ates an ampere-conductor distribution that interacts with the field distribution to produce a net unidirectional torque. The frequency of the induced current in the conductor is affected by the speed of the rotor on which it is located; however, the relationship between the rotor speed and the frequency of the armature current is such as to yield a resulting ampere-conductor distribution that is stationary relative to the field distribution of the stator. As a result, the singly excited induction machine is capable of producing torque at any speed below synchronous speed. For this reason, induction machines are placed in the class of asynchronous machines.