Purpose built teaching equipment for a laboratory based course in three phase machines and drives

Abstract

The hazards associated with high voltage three phase inverters ond the rotating sha@s of large electrical machines have resulted in most of the engineering courses covering these topics to be predominantly theoretical. This paper describes a set of purpose built, low voltage and low cost teaching equipment which allows the "hands on I' instruction of three phase inverters and rotating machines. By using low voltages, the student can experiment freely with the motors and inverter and can access all of the current and voltage waveforms, which until now could only be studied in text books or observed as part of laboratory demonstrations. Both the motor and the inverter designs are optimized for teaching purposes, cost around $25 and can be made with minimal effort.

A project-oriented approach for power electronics and motor drive courses

“…The servo drive used in the PE and VSD courses is composed of four main modules as shown in Figure 1; these modules and other parts are numbered from (1) to (6) and a listing of the parts used are shown in Table 1.…”

“…This signal is then amplified and positive-shifted in the conditioning module (5). The circuit for the analog signal conditioning module shown in Figure 2 uses operational amplifiers to add an offset voltage to the AC signal from the current sensor, thus making it always positive for the analog to digital converter (ADC) located in the DTC module (6). The offset voltage is adjusted with R1 trimmer while the amplifier gain is adjusted with R5 trimmer.…”

“…A problem commonly encountered in these courses is that students are overwhelmed by the mathematical analysis and the complex equations it entails, but mostly by the difficulty of putting theory into practice. There are surveys 6,7 which have verified that a more practical approach in class enhances student motivation and understanding of the application of theoretical content.…”