Manali: Himachal Pardesh

Motor Types and Parts

Motor Types and Parts Rotor: 2 Types Squirrel cage rotor Iron core Embedded conductor Wound rotor Stator parts Coil winding Shading band Stator pole Inside coil Outside coil Bearings…ball or sleeve Frame…totally enclosed/vented/hermetic Parts of the Motor Fan End bell Electrical connection box Winding Stator Rotor External shaft End bell Motor Enclosures Totally open motor Vents on sides + end Modified totally open motor Vents on ends only Open drip-proof motor Drips of liquid will not enter Totally enclosed (non-vent motor) Generally used when subjected to moisture Sleeve Bearings Lubricated by coil…..SAE 20, 30 0r refrigeration oil 200 or 300 Wicked system…consisting of a cotton or wool with in an oil reservoir Slip Ring….consisting of brass clip ring on the motor shaft as the shaft turns the  ring turns slowly picking up oil from an oil pocket. Ball Bearings Lubricated by grease. These may be sealed or serviceable Oil-less Bushing A shaft passes through a sintered (porous bronze) bushing.  The bushing has been impregnated with oil at the factory considered to be permanently lubricated.  Used on low Hp. Fan Motors Motor Starting Devices/ Characteristics Motor Starting Devices/ Characteristics Start Winding A winding that is placed in the stator closer to the rotor than the main (run) winding Connected in parallel with the run winding Placement in the stator is such that the start winding is physically 90 degree away from the run winding The start winding is constructed of smaller wire and may more turns than the run winding The start winding has a high resistance and a high inductance than the run winding Which results in a phase shift between the winding The resulting phase shift cause a rotating magnetic field to be setup in the stator and rotor, which starts the motor Start Capacitor: Is connected in series with a start winding to increase the phase shift created by the start winding Shading Coil A copper strap is used to separate a small portion of the run winding

Three Phase Motors

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