Contents
            • ABSTRACT
            •
             INTRODUCTION
            •
             BASIC OPERATION OF ELECTRIC MOTORS
            •
             WRITTEN POLE MOTOR DESIGN
            •
             OPERATIONAL BENEFITS OF WRITTEN POLE MOTORS
            •
             CONCLUSION
            •
             REFERENCES
            ABSTRACT
       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. 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
             In the 1990’s, a new concept was developed in 
         electric motors called the Written Pole® electric 
         motor. This new motor type dramatically 
     N   reduces starting currents of single phase 
     O   motors. The motor uses an innovative approach 
     I
     T   of controlling the magnetic field of the motor to 
     C   reduce the starting current requirements. The 
     U   result is a motor that has starting current 
     D   requirements of only about twice the normal 
     O   running current and, as an added benefit, the 
     R   motors have efficiencies of 90% or better 
     T
     N   compared to conventional motors, which have 
     I   efficiencies of around 85%. 
    Basic operation of electric motor
        To understand how an electric motor works, we must first 
    understand the principles of magnetism and 
    electromagnetism. An electromagnet is simply a piece of iron 
    or other ferrous material that has been wound with a 
    conductor through which an electric current can pass. When a 
    current is passed through the conductor the iron is 
    magnetized and acts just like a permanent magnetic. Consider 
    two electromagnets and one permanent magnet aligned as 
    shown in the figure below.
     TW0 POLE ELECTO-               The top electromagnet is oriented 
     MAGNETIC                     with the north-pole pointing up. The 
                                  middle permanent magnet is 
                                  oriented in the reverse fashion, with 
                                  its north-pole pointing down and the 
                                  bottom electromagnet has its north 
                                  pole pointing up. There will be a 
                                  force of repulsion between the 
                                  centre magnet and the other two 
                                  since the south pole of the top 
                                  magnet is aligned with the south 
                                  pole of the centre magnet and the 
                                  north pole of the bottom magnet is 
                                  aligned with the north pole of the 
                                  centre magnet.