Patent ID: 7224768

Claim:
An X-ray tube device comprising: an anode rotation mechanism for rotating an anode in the X-ray tube device with a motor; and an anode rotation number detecting means for detecting the rotation number of the anode on the basis of information of voltage and current or of current only related to a stator coil for generating a rotating magnetic field to rotate the motor, wherein the anode rotation number detecting means includes; voltage detecting means for detecting voltage of the stator coil: at least one current detecting means for detecting current flowing through the stator coil; impedance calculating means for calculating impedance of the anode rotation mechanism using an output of the voltage detecting means and the current detecting means; initial impedance storing means for storing an impedance at the start of anode rotation calculated by the impedance calculating means; impedance ratio calculating means for calculating a ratio between the initial impedance and a present impedance calculated by the impedance calculating means; and means for detecting when the rotation number of the anode is a predetermined rotation number by judging when the impedance ratio calculated by the impedance ratio calculating means reaches a predetermined value.