Abstract:

The paper shares experience in teaching the methods of starting wound rotor induction motors, in particular, the calculation of the starting resistances into the rotor circuit and the characteristics of the start-up process, with the help of a program developed for the purpose in a virtual environment.

The largest share (about 60%) of the electrical energy consumed in the world is occupied by electric motors. Asynchronous motors are the most widely used motors. Asynchronous motors are considered the universal machine of the manufacturing industry. It is estimated that they are applied in 70%-80% of all industrial propulsion applications. This is the reason why they are thoroughly studied by the students of the Electrical Supply and Electrical Equipment major.

One of the problems with asynchronous motors for high power is the large inrush current. It is unfavorable both for the engine itself and for other consumers included in the electrical circuit. Therefore, when starting asynchronous motors for large power, different ways are used to limit the inrush current. Wound rotor motors can be started with a low inrush current, by inserting high resistance into the rotor circuit. This leads to a reduction in the rotor and stator current and a change in the mechanical characteristics and critical slip of the motor while increasing the starting torque. Therefore, an important part of teaching induction motors is for students to be able to calculate these resistances as well as the characteristics of the starting process. They receive projects for independent work, which include the calculation of resistances and the characteristics of the start-up process.

A program has been developed to assist the resistance calculation process. At the same time, the active role of students is preserved, because they must take certain decisions in the process of its implementation.

The proposed program also helps the teachers to independently check the completed projects of the students.

The proposed methodology and the program developed based on it have been approved in the training course for students from the students majoring in "Electrical Engineering" and "Electrical supply and electrical equipment" at the Faculty of Physics and Technology at the University of Plovdiv “Paisii Hilendarski” (Bulgaria). The use of the proposed program during the e-learning of the students due to Covid-19 was particularly useful.

Keywords:

Wound rotor induction motor, Education, Electrical Engineering.