X-ray CT apparatus and a method for detecting magnetic pole position thereof

A method for detecting a magnetic pole position of a direct drive (DD) motor type X-ray CT apparatus that includes a fixed gantry having a plurality of stator coils mounted thereon and arranged in a circle, and a ring-shaped rotation frame having a plurality of rotor magnets facing the plurality of stator coils, the method comprising:

• activating a magnetic pole position detection function at a start-up time;
• based on the activation of the magnetic pole position detection function, applying a current to the plurality of stator coils;
• applying a brake load to the rotation frame;
• and
• detecting a magnetic pole position of a said rotor magnet based on a number of encode pulses generated between a vibration start-up time and a vibration stop time, where the vibration starts in response to the application of the brake load.

An X-ray CT apparatus comprising:

• a fixed gantry having a plurality of stator coils mounted thereon and arranged in a circle;
• a ring-shaped rotation frame having a plurality of rotor magnets facing the plurality of stator coils;
• an X-ray tube and an X-ray detector situated on the rotation frame to face each other;
• a supporting means for providing non-contact support of the rotation frame on the fixed gantry;
• a magnetic pole detection means for detecting a magnetic pole position of one of said rotor magnets at a start-up time of the plurality of stator coils;
• and
• a braking means for applying a brake load to the rotation frame when detecting the magnetic pole position and for removing the brake load after detecting the magnetic pole position.