Car wiring diagrams: Auto Transformer Basics Wiring Diagram, wiring diagram, wire wiring harness, schematic circuit diagram, wiring diagran, wireing diagram, wirring diagram, wiring daigram, wiring diagrams. What is a wiring diagram? Learn about wiring diagram symbools. Read how to draw a circuit diagram. See wiring diagram examples..Electrical Tutorial about the Autotransformer and the Variable Auto transformer called the Variac used in Schools and College Labs.In the diagram the windings of the same phase are colored same for easy understanding. The Vector diagram shown below is also colored. The arrows denote the voltage .