⁴⁵If you examine the induction disk from a 51 relay, you will note a that the disk’s radius is not constant, and that there is actually a “step” along the circumference of the disk where its radius transitions from minimum to maximum. The amount of disk material exposed to the stator coil’s magnetic field to generate operating torque therefore changes with rotation angle, providing a nonlinear function altering the shape of the relay’s timing curve.