I was looking for a really good book on understanding controls for the electrician. And also VFDs. alot of the books i've seen look as though they are written for an electrical eng. or for testing purposes. I'm interested in a troubleshooting book or any book that you , as a jw electrician might refer to while doing control work.I would like to take a call for this type of work, but dont want to be totally cold going in. I know there is classes, but I love to learn from books on my own time.