1 hvac214 - oil electrical motors part 1 motors part 1
TRANSCRIPT
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HVAC214 - Oil ElectricalHVAC214 - Oil Electrical
Motors Part 1
Motors Part 1
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MotorsMotors
• Motors consist of a stationary part called the stator that surrounds a rotating part called the rotor.
• One or more windings are mounted on the stator.
• There are no windings usually on the rotor.
• Motors consist of a stationary part called the stator that surrounds a rotating part called the rotor.
• One or more windings are mounted on the stator.
• There are no windings usually on the rotor.
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Parts of a motorParts of a motor
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MotorsMotors
• The rotor, or the center part of the motor is not connected to any external source of voltage.
• When the winding on the stator is powered it generates a magnetic field.
• As the A/C changes from a positive to a negative this magnetic field will rotate.
• The rotor, or the center part of the motor is not connected to any external source of voltage.
• When the winding on the stator is powered it generates a magnetic field.
• As the A/C changes from a positive to a negative this magnetic field will rotate.
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MagnetsMagnets
Like poles of a magnet will repel each other. Unlike poles will attract each other.
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MotorsMotors
• As you remember like poles of a magnet repel each other.
• As the magnetic fields of the stator windings change from positive to negative it “chases” the rotor as the poles on the rotor are positive and negative.
• As you remember like poles of a magnet repel each other.
• As the magnetic fields of the stator windings change from positive to negative it “chases” the rotor as the poles on the rotor are positive and negative.
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MotorMotor
• This constant changing of the magnetic field will keep a motor running.
• The problem comes when you are trying to start a motor. If the magnets are lined up evenly between poles the motor would not start.
• This is the purpose of the start winding.
• This constant changing of the magnetic field will keep a motor running.
• The problem comes when you are trying to start a motor. If the magnets are lined up evenly between poles the motor would not start.
• This is the purpose of the start winding.
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Start and Run WindingsStart and Run Windings
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Start WindingStart Winding
• This is an additional winding in a single phase motor that allows the motor to start when the poles of the stator and rotor are not in the correct position.
• The current applied to the start winding is slightly out of phase with that applied to the run winding.
• This is an additional winding in a single phase motor that allows the motor to start when the poles of the stator and rotor are not in the correct position.
• The current applied to the start winding is slightly out of phase with that applied to the run winding.
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Run windingRun winding
• This is the winding on the stator that allows the motor to continue to operate.
• The run winding gets constant voltage until the motor shuts off.
• This is the winding on the stator that allows the motor to continue to operate.
• The run winding gets constant voltage until the motor shuts off.
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Shaded Pole MotorShaded Pole Motor
• The shaded pole motor is the simplest motor.
• It has one winding surrounding a laminated core.
• It uses a shaded pole to determine its rotation.
• The shaded pole motor is the simplest motor.
• It has one winding surrounding a laminated core.
• It uses a shaded pole to determine its rotation.
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Shaded Pole MotorShaded Pole Motor
• The shaded pole motor consists of a squirrel care rotor, an iron core and two or more rings (poles) with a coil and small copper inserts.
• The insert slows the buildup of the magnetic field just enough to cause rotation towards the magnetic field.
• The shaded pole motor consists of a squirrel care rotor, an iron core and two or more rings (poles) with a coil and small copper inserts.
• The insert slows the buildup of the magnetic field just enough to cause rotation towards the magnetic field.
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Shaded Pole MotorShaded Pole Motor
• The action provides for induced magnetism into the rotor.
• The rotor will then turn as if it is attracted by the magnetism.
• Movement of the rotor will continue as long as there is change of the polarity of the poles and the rotor.
• The action provides for induced magnetism into the rotor.
• The rotor will then turn as if it is attracted by the magnetism.
• Movement of the rotor will continue as long as there is change of the polarity of the poles and the rotor.
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Shaded Pole MotorsShaded Pole Motors
• If the motor stalls or if the bearings freeze the motor windings will usually not burn out.
• When the motor is in a locked condition the windings draw very little current.
• The direction of a shaded pole motor is towards the shaded pole.
• If the motor stalls or if the bearings freeze the motor windings will usually not burn out.
• When the motor is in a locked condition the windings draw very little current.
• The direction of a shaded pole motor is towards the shaded pole.
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Shaded Pole MotorShaded Pole Motor
• Shaded pole motors can be made multiple speed by inserting voltage taps into the motor winding.
• Shaded pole motors are low in cost but have a very low starting torque and a very low power factor.
• Shaded pole motors can be made multiple speed by inserting voltage taps into the motor winding.
• Shaded pole motors are low in cost but have a very low starting torque and a very low power factor.
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Shaded Pole Motor ExampleShaded Pole Motor Example
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Shaded Pole MotorShaded Pole Motor
• Shaded pole motors are built for very small sizes and are used for light duty in small appliances.
• In refrigeration shaded pole motors are frequently used for Evaporator fan motors.
• Shaded pole motors are built for very small sizes and are used for light duty in small appliances.
• In refrigeration shaded pole motors are frequently used for Evaporator fan motors.
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Split Phase MotorsSplit Phase Motors
• Split phase motors are also called induction start - induction run motors.
• These motors use a current relay or a centrifugal switch to remove the start winding from the circuit.
• The start windings work on a phase shift principle.
• Split phase motors are also called induction start - induction run motors.
• These motors use a current relay or a centrifugal switch to remove the start winding from the circuit.
• The start windings work on a phase shift principle.
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Split Phase MotorSplit Phase Motor
• The voltage from the start winding to the run winding is 10 degrees out of phase.
• Starting torque and running torque are relatively low in split phase motors because the phase shift is so low.
• The voltage from the start winding to the run winding is 10 degrees out of phase.
• Starting torque and running torque are relatively low in split phase motors because the phase shift is so low.
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Split phase motorsSplit phase motors
• These motors are used for belt drive blower applications such as small appliances like:– Washers– Dryers– Dish washers– Some older furnace blowers
• These motors are used for belt drive blower applications such as small appliances like:– Washers– Dryers– Dish washers– Some older furnace blowers
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Split Phase MotorsSplit Phase Motors
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Split Phase MotorSplit Phase Motor
• The centrifugal switch removes the start winding from the motor circuit once the motor reaches around 75% of its rated speed.
• This is the part that most often fails when a motor is started and stopped many times.
• The centrifugal switch removes the start winding from the motor circuit once the motor reaches around 75% of its rated speed.
• This is the part that most often fails when a motor is started and stopped many times.
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Centrifugal SwitchCentrifugal Switch
• The switch is normally closed when the motor is not operating.
• The switch is normally closed when the motor is not operating.
Centrifugal Switch