It instead compensates by automatically selecting different power taps on the autotransformer. An example of an autotransformer is an automobile ignition coil. The substation received a new 12/24 kV autotransformer in April 2015. An autotransformer starter was patented in 1908. The equivalent power rating of the autotransformer is lower than the actual load power rating. These are important safety considerations when deciding to use an autotransformer in a given application. An autotransformer is an electrical transformer with only one winding. The variable ratio of the autotransformer compensates for the voltage drop along the line. The autotransformer winding has at least three taps where electrical connections are made. The autotransformer is connected to the bus bars by an additional circuit breaker. An autotransformer consist only one winding that is tapped at some point along the winding. Six autotransformer stations, spaced an average of 3.8 miles apart along the line, converted power.