Rotating Anodes

Question 1

What is the function of a rotating anode ?

Answer 1

To rotate the x ray tube and expose more parts of the (tungsten) anode over time to improve heat dissipation and power output. This allows for longer exposure times and improved image quality and less damage to specific parts of the anode.
This is done is the exposure prep stage.

Question 2

What are the phases of rotating anode prep ?

Answer 2

Start which supplies the anode with 2 phase A.C. Then after 0.8 seconds, the anode reaches maximum speed and switches to run mode which is single phase A.C. When prep mode is done, D.C can be applied to break the circuit

Question 3

What rpm is the rotating anode at and what is the resonant rpm of glass ?

Answer 3

8500 rpm is the maximum speed. 6500 rpm is the resonant frequency of glass.

Question 4

How does the rotating anode control circuit determine the mode ?

Answer 4

The rotating anode contains a stator which has wirings for start and run modes.
When going into prep, the start winding experiences A.C current due to the capacitor and the open disconnection switch before it in the circuit.
When motor hits the correct speed, the start phase disconnects and instead goes to the run wiring.
When the open switch is closed, DC is put into the wiring causing the circuit to break.
Windings use electromagnets to rotate.