The extinction angle is the angle at which the current in a coil or winding reverses its direction. By controlling the extinction angle, it is possible to regulate the amount of time the current flows in each coil, which in turn affects the overall performance and efficiency of the machine.
In DC machines, extinction angle control is achieved by shifting the brushes or commutators relative to the armature windings. In AC machines, it is accomplished by adjusting the timing of the firing pulses to the stator windings.
Proper extinction angle control helps to minimize sparking and arcing at the brushes or commutators, reduce power losses, improve commutation, and ensure smooth operation of the machine. It also helps to optimize the torque and speed characteristics of the machine.
In summary, extinction angle control is a crucial technique used to regulate the flow of current and optimize the performance of rotating electrical machines.