14-12-2012, 06:17 PM
WRITTEN POLE ELECTRIC MOTOR
WRITTEN POLE ELECTRIC.pptx (Size: 1.16 MB / Downloads: 134)
INTRODUCTION
Electric motors are the back bone of electrified society.
90% of industrial applications induction machines are used.
Induction machines have certain drawbacks, to overcome this written pole electric motors are used.
It works on the principle of written pole technology.
WRITTEN POLE MOTOR
Developed by precise power corporation with the help of electric power research institute (EPRI).
Conventional motor have a fixed even no discrete field pole structure.
Written pole operates as variable no of poles.
Special magnetic layer on the rotor and special exciter winding in stator.
Magnetic layer is magnetised or written in to any desired magnetic pole pattern by exciter during operation.
High resistance rotor cage limit starting current and provide starting torque.
Written pole technology allow single phase motor designed up to 100 hp
Controlling the. magnetic field of the motor to reduce the starting current requirements of only about twice the normal running current Motors have efficiencies of 90-97%.
EXCITER WINDING
concentrated exciter located at one or two points of the stator winding.
The the portion of the rotor's magnetic layer that is immediately across the air gap from it, this winding is used to maintain the correct pole geometry in the rotor.
Energy required for operation of the excitation winding is magnetically coupled through the stator core
No need of external energy source.
ROTOR CONSTRUCTION
The rotor is a combination of induction, hysteresis and permanent magnet technology.
Steel shaft inserted into lamination stack containing a high resistance rotor cage.
The high resistance cage limits the starting current and provides induction torque during starting.
Laminations are constructed using low loss, electrical grade steel.
The total cross sectional area and resistivity of the rotor cage are selected so as to provide high slip, high power factor starting characteristics