A little hands on experience with transformers will go a long way. In my experience transformers work wonderfully for the purposes they are specifically designed for but they have a greater tendency to NOT be very ideal when one tries to repurpose them for other applications. This lab is meant to help you experience some of those realities.

Purpose:

In this lab all we are going to do familiarize ourselves with transformers of different types. We will measure the winding number and whether real transformers behave in a manner consistent with ideal transformers. We will also explore whether these characteristics are frequency dependent. You will need to apply the lab skills you have been developing thoughtfully. You will not really need to use the breadboard since clip leads of various types will probably be more useful. You will probably notice that you are not asked to make a frequency plot for this lab.

1) Your first transformer will be some sort of step down transformer from a "wall wart" that we tend to use everywhere in our modern tech lives. Because we are using the function generators to drive the primary coil of our transformers please be extra careful to make sure there is roughly 1 kΩ between the function generator and the coil. In most cases the usual primary coil will be sort of obvious but see if you recognize the clues.

2) Start by using a modest 60 Hz AC signal of about 1 V peak to peak and see what the output at the secondary is. You can start by measuring the output voltage directly since the oscilloscope acts like a very large load impedance. Be aware that, because of the 1 kΩ resistor the primary voltage to the transformer is NOT the same as the function generator output. You will need to sort out how to measure both the input and output voltages (not at the same time probably). You are likely to notice a phase shift between the voltage drop across the primary relative to the input voltage. Determine the primary inductance from that phase shift. By looking at the secondary voltage relative to the primary voltage you can determine the winding number for your transformer. Now explore across the range of frequency possibilities and determine to what extent the performance characteristics of the tranformer vary with frequency (no plot needed). Describe and explain what you observe.

3) Place a load resistor of roughly 100 Ω and 10 kΩ on the secondary and see if there is an effect on the input impedance. Describe and explain that effect.

4) Next, reverse the primary and secondary coils and repeat the explorations of part 2).

5) Lastly you will repeat your explorations with a different transformer which will hopefully have less predictable behavior.

Deliverables:

I) The usual date, description of equipment, lab partners, etc etc for openers. This will be followed by your fascinating description of the results of your investigations into the performance of transformers and their idealness or lack of it. This is your last lab so your ultimate success at keeping an effective and appropriate lab notebook will be based on this lab.

 

Thanks in advance for the thoughtful discussion!!