Construction of 3 Phase Induction Motors Flashcards
Stator
Function: Creates the rotating magnetic field.
Components:
Core: Made of laminated silicon steel to minimize eddy current losses.
Windings: Insulated copper wire arranged in slots to produce a three-phase field.
Housing: Cast iron or aluminum for structural support and heat dissipation.
Squirrel cage rotor
Construction: Copper or aluminum bars embedded in a laminated steel core, short-circuited by end rings.
Advantages: Simple, robust, and low maintenance.
Wound rotor
Construction: Copper windings connected to external resistors or controllers via slip rings.
Advantages: Allows speed and torque control.
Air gap
Function: Small gap between stator and rotor to facilitate magnetic coupling.
Bearings
Function: Support the rotating rotor.
Materials: Steel or ceramic.
Frame & end covers
Function: Provide mechanical support and protect the internal components.
Materials: Cast iron or aluminum.
Cooling system
Function: Dissipates heat generated during operation.
Components: Fans or fins on the rotor or stator housing.
Slip Rings (wound motors only)
Function: Transfer current to external circuits for control.
Materials: Copper or brass.
Materials used
Stator Core and Rotor Core:
Laminated silicon steel to minimize hysteresis and eddy current losses.
Rotor Bars:
Squirrel cage: Cast aluminum or copper for electrical conductivity.
Wound rotor: Copper windings insulated with varnish or enamel.
Windings: High-purity copper for low resistance and high efficiency.
Advantages of squirrel cage
Simple design with no maintenance-intensive parts like brushes or slip rings.
Used in most applications due to reliability.
Advantages of wound rotor
External resistance allows control of starting torque and speed.
Preferred in applications requiring variable speed or high starting torque.
