Written-Pole technology is a revolutionary, yet fundamentally simple approach for enhancing the performance of electric motors and generators.

The application of Written-Pole technology frees engineers from one of the most basic constraints faced by designers of conventional induction and synchronous machines.

The Written-Pole motor is a hybrid concept, which utilizes basic concepts from induction, hysteresis and permanent magnet motors, with several important distinctions.

Unlike conventional designs, where the magnetic poles are fixed by the geometry of the rotor cage and stator windings, Written-Pole machines incorporate a proprietary concept that optimizes the magnetic geometry of the rotor for peak performance as the operating speed of the machine varies.


Written pole motors combine the advantages of both induction motors and synchronous motors. Both motors and generators are constructed using written pole technology. Written pole is a patented technology which has been developed by precise power corporation in United States with assistance from the Electric Power Research Institute (EPRI).


A concept that appears to break many of the established traditions governing the design of rotating electric machines, Written-Pole technology offers
an interesting alternative to conventional electric motors and generators.

Motors using Written-Pole technology combine the efficiency and constant-speed characteristics of a synchronous motor with the high-starting torque of an induction motor. Written-pole motors offer an elegant solution, as they only require starting currents less than twice the running current and therefore can be applied directly in the 10- to 100-hp range with single-phase service.

They also have efficiencies of the order of 92%, compared with 85% for conventional motors. Although written-pole motors are more expensive, the savings on distribution technology and the increased scope for motor application on existing single phase or heavily loaded lines will often outweigh this cost disadvantage.

They are thus likely to find significant application potential...