 Max Korndörfer claimed four methods of using an autotransformer for reduced voltage motor starting.Three of the methods are not used by the industry and it is the 4th method of starting that has been in use for more than a hundred years

The fourth method is with the star switch closed and as the motor accelerates a change over is made from the reduced voltage tap on the autotransformer to direct-on-line.The starting sequence is