Take a look at the talley plate on the transformer. It will tell you what the rating (kVA) is, voltages, etc. It will also tell you what type it is. Look at the diagram. Then tap the type of transformer into the internet and all kinds of stuff should pop up. Maybe the guy just didn't feel like giving you info on it. I would find it very hard to believe that an electrician wouldn't know BASICS of transformers. If I were you I would find out as much as you can.
