Study on the Sensorless Automatic Detection of the Rotor Displacement in Active Magnetic Bearing Liu Xuedong Liu Quan Hu Yefa Master Student,School of Information Engineering, WUT, Wuhan 430070,China.A new method of detecting rotor position in the magnetic bearing was studied. The linear relationship between the air gap variation and inductance variation was deduced in theory. A set of measures was proposed to obtain a feedback signal. A control circuit was represented for reference.active magnetic bearing; sensorless; small high frequency voltage for testing; position detection