Bee Presentation 1 PDF

Three phase Induction Motor Advantages ▪ Three-phase induction motors are the most common and frequently used machines in industry ▪ Simple design, rugged, low-price, easy maintenance ▪ Wide range of power ratings: f...

Three phase Induction Motor Advantages ▪ Three-phase induction motors are the most common and frequently used machines in industry ▪ Simple design, rugged, low-price, easy maintenance ▪ Wide range of power ratings: fractional H.P. to 10 MW ▪ Run essentially as constant speed from zero to full load ▪ Robust; No brushes. No contacts on rotor shaft (Squirrel Cage) ▪ High Power/Weight ratio compared to DC motor, Lower Cost/Power ▪ Speed is frequency dependent Stator and rotor Working Principle  Comparison Squirrel Cage and Slip ring induction motor Feature Squirrel Cage Slip RIng Construction Construction is simple Construction is complicated. Rotor Rotor bars made up of aluminum Three phase winding like stator End/Slip Rings Rotor bars (rotor conductors) are short- The three-phase windings are connected to the circuited with the end rings. slip rings External External resistance can not be added in rotor External resistance can be added in the rotor Resistance circuit because the rotor bars are circuit to limit starting current as well as permanently short-circuited. increase the torque. Starting Torque Lower starting torque compared to wound Higher starting torque rotor motors Speed Control Speed control using rotor resistance is not Easier speed control by varying the external possible as the rotor bars are shorted resistance connected to the rotor winding Efficiency Higher efficiency under normal operating Lower efficiency due to the additional losses in conditions the external resistors and brushes. Maintenance maintenance-free as there are no brushes or Requires periodic maintenance of slip rings slip rings. and brushes. Cost Generally lower cost due to simpler Higher cost due to the additional components construction. and maintenance requirements.  Applications Squirrel Cage Slip RIng Moderate starting torque, constant speed High starting torque, Variable speed Fans Lifts Blowers Cranes Pumps Hoists lathe machine Elevators drill machine conveyors Industrial Drives Printing Presses Floor Mills Hoists Large ventilating fans Mining Wind turbine