Modular laboratory equipment for undergraduate and technician courses in power electronics

Abstract

This paper describes the experience gained with the development and use of modular teaching equipment for the Power Electronics Laboratory in the Federal Center of Technology Education of the state of Minas Gerais, Brazil. Conception, construction as well as pedagogic issues are addressed. The equipment was developed to be cost-effective, safe, easy to use, flexible and robust. Experiments contents are also presented. It will be shown that the developed equipment allowed straightforward realization of several hands-on experiments on DC motor drive, monophase inverters, some non-isolated PWM choppers and DC-DC converters topologies, line commutated monophase and threephase controlled and uncontrolled rectifiers. The equipment can also be used in higher levels power electronics courses, since it is modular. I. INTRODUCTION Laboratory experiments in undergraduate courses are often used to assist and complement the classroom lectures. They are an important tool for improving student's hands-on skills like measuring, corroborating practical results, comparing theory and practice, modeling, etc. But the complexity of the power electronics systems makes the laboratory experiments implementation not so simple. The Power Electronics field is very multidisciplinary, and several authors have mentioned this fact (1,2,3,6). There are also class time restrictions in virtually all courses, and one of the lecturer's challenges is to adjust the deepness and the broadness of the used approach (3). When implementing practical power electronic converters, EMI and parasitic elements issues can ruin the results if not observed and correctly managed. In this context, a well planned teaching equipment can help a lot. It can save class time and spur student's motivation. The power electronics group at the Centro Federal de Educacao Tecnologica de Minas Gerais (Federal Center of Technology Education of the state of Minas Gerais) - CEFET-MG, has been developing equipment for the electronics technician course and for the electrical engineering course since the year 2000. The key idea is to provide the power electronics laboratory with cost-effective, robust, flexible, safe and easy to use teaching equipment, which could make the laboratory classes more profitable than they were in their earlier versions. It should be pointed out that the equipment have been planned and assembled entirely in the school, using simple resources. The power electronics curricula of the electronics technician course and the electrical engineering courses at CEFET-MG are covered in two semesters. Both curricula share most common subjects and the laboratory as well. The basic difference is the approach's deepness and the use of calculus in the undergraduate level. The focus is on the basic principles of the power electronics converters. Simulation resources are used as an aid, and excellent results have been achieved with the demo version of the Psim package from Powersim (7). The discussion about this topic will be presented in a further work. In a previous paper (1), we discussed some laboratory experiments approaches and presented assembly details of the developed modules. Also, some modules like the phase- controlled rectifiers have been presented. In this paper it will be presented the new developed modules (section II), as well as some experiments and its results (section III). II. SOME DEVELOPED MODULES Regarding modularity, the adopted concept was to divide the power electronics systems in up to three modules: the power converter module, which comprises the switching devices and the energy storage elements, the command / control module and finally the gate driver modules. It was found that this arrangement provides a better understanding by the students and the utilization of the modules in a broader diversity of experiments. Figure 1 shows the block diagram of the fragmented system.