STEP-BY-STEP METHOD TO IMPROVE PROFICIENCY IN ELECTRICAL MACHINE LAB ACTIVITIES
University of Castilla-La Mancha (SPAIN)
This paper proposes a learning method aimed to improve student proficiency during electrical machine lab activities. The motivation for developing such method has is origin in the experience of the author in teaching electrical machine in the Industrial Engineering course at the University of Castilla-La Mancha for the last eight years. Laboratory activities of the fundamental course on electrical machines consist of five assignments, for which students are requested to manually mount the electrical circuits for testing and measuring transformers and induction machines.
In the first six years, students could check lecture notes and were provided with a detailed outline of the activity as well as complete schemes of the circuits that had to be mounted. Despite the available information, most of the students showed clear difficulties in mounting the circuits. This resulted in long execution times, blowing several fuses and, in some cases, damaging instruments. The main reason for the high rate of issues encountered by the students appeared to be the fact that most of the students tried to reproduce the circuital schemes that they found in the activity notes. Unfortunately, this way of mounting a circuit is highly error prone. Moreover, the student can test the circuit only once it is finished. If the circuit does not work properly, it is hard to understand which are the wrong connections. Finally, since the students simply try to copy a scheme, does not really focus on the meaning of each connection and tends to achieve only surface learning.
In the last two years, a different strategy has been experimented during lab activities. Students are not provided with the circuital schemes but are just explained what is the purpose of the activity that they have to carry out. Before starting the first lab activity, students are thaught a simple but systematic step-by-step method to mount the circuits.
The steps are the following:
1. To mount the main circuit, without any measurement. Since the basic circuit basically consists of connecting a feeder to a machine, this step is not generally error prone.
2. To connect instruments for series measures, first ammeters and then the series connection of wattmeters. This appears to be the most critical step. Generally it helps if the students understand that each series measure only requires one additional cable.
3. To mount the parallel connections of wattmeters and voltmeters. This step does not generally create any issue.
The strategy described above has at least three relevant advantages with respect to the naïve approach that students tend to apply, as follows:
1. At each step, the circuit, even though incomplete, is fully functioning. So the students can check if the inserted instrument works or can revise the circuit if it is not working.
2. The students are forced to focus on the purpose of each instrument, since they cannot follow a circuital scheme. Even in case they want to sketch a scheme before starting to mount the physical system, they have to think on the way of connecting each instrument. In any case, the students are forced to achieve deep learning.
3. While errors are always possible, the step-by-step method highly reduces the possibility of creating short circuits or other potentially dangerous connections. As a matter of fact, students that have been using the proposed step-by-step method seldom blow fuses and have never damaged any instruments.