INDUCTION MOTORS

—This name designates that type of alternating current motors in which currents are induced in the windings on the rotor of the motor. These in turn generate the magnetic fields nece ary to produce rotation, These motors consist of, 1st., a rotor | made up of disks of laminated iron; in} Mie slots dno on their sat a periphery aso conbocea are placed often is iti tints a tects inner - surface in which are placed the stator or "BERRA: Jintines., Mas The wringing on the Sole iney Ca) be striae 20 that alternating ot tho| current generator. The winding on the stator, with the ends connected to anN|/fish external resistance through slip rings; the motor is then called a Wound Rotor Machine; (B) consist of copper bars in| the slots referred to above, their ends con- | nected by two rings of copper; in this case the motor is of the Squirrel Cage type. In polyphase motors, when the field is energized, the pulsating fields, generated by each phase combine to form a rotating field. This cuts the rotor windings, generating current in them, the reaction of which causes the rotor to follow the rotating field. The rotor must always | & lag a certain amount (called the slip), in order that the current may be generated inits windings. Single phase motors will not start themselves, but when started, the rotor windings generate a pulsating in field which combines with that of the stator, resulting in a rotating field which produces the action noted above. There are two common methods of starting single phase motors: (1) ‘shading coils’ on of high impedence, so wound on the OT aie an ie case A field to produce a rotating one; (2) the after motor is attaining started as a a repulsion cortain speed motor and the | | *° brushes are lifted and the windings short-| circuited by an automatic device.