Three Phase Motors

Squirrel Cage Induction

Squirrel cage induction motors are the most common type of three phase motors used in the HVAC and refrigeration industry

Advantages

•  No starting relays required

•  High starting torque

•  High running torques

•  Easily reversed

•  No adjustable speed

Wound Rotor Induction

•  Characteristics

•  used primarily as a variable speed motor

•  Stator same construction as squirrel cage motor

•  Wound rotor

•  Slip rings, brushes , brush holders

•  Rotor

•  3 Single phase windings 120 degrees apart

•  Same # of Poles as the Stator

•  Leads connected to external speed control

(Varies the Resistance for speed control)

•  Speed controlled by

•  Timing Relays

•  Contactors

•  Push Button Speed Select

Types of Stator Windings for Both

•  Wye Wound

•  Delta Wound