Introduction and overview of "Written-Pole" technology

A new type of AC machine has been developed which can provide performance beyond the capability of conventionally designed machines. This new “Written-Pole” machine technology consists of a rotor design that has a layer of magnetic material that can be changed magnetically to any desired pole pattern while the machine is operating. In conventional machines the rotor poles are mechanically located and the magnetic pattern (or poles) can not be altered after the machine is assembled. The ability to electrically place the magnetic poles is any position allows a synchronous motor to be built that has a very low per-unit direct line starting current, high operating efficiency, and very high inertial load starting capacity. It can also provide generators where the output frequency is independent of rotational speed. The author describes the construction of the Written Pole machine, its starting characteristics, high inertial load applications and large single phase Written Pole motors