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POWER SYSTEMS SALES TRAINING
Purpose of an AC Motor
Electrical
EnergyMechanical
Energy
The purp ose of an AC Motor is to
Convert Electr ical Energy into Mechanical Energy
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POWER SYSTEMS SALES TRAININGTypical Motor Components
Lubrication and Pipe
Plugs
Eyebolts
Computer
Designed
Inner Bearings Caps
Shaft Run Out
Open Bearing
ConstructionModern Non-
hygroscopic
Insulation System
Integrally
Cast Frame
PositiveLubrication
System
Non-Sparking, CorrosionResistant and
Bidirectional Cooling Fans
Rotatable
Diagonally Split
Conduit Boxes
Cast Iron
E
nd Shields
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POWER SYSTEMS SALES TRAINING
AC Motor ConstructionStator
Laminations
Stator WindingAssembly
Motor Shaft
Die-cast
RotorAssembly
3 Phase Winding Circuit w/Connections T1, T2 & T3
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POWER SYSTEMS SALES TRAINING
AC MOTOR CONSTRUCTION
Stator Winding
Assembly
Rotor
Assembly
Motor Frame
Assembly
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POWER SYSTEMS SALES TRAINING
Bar Magnet
N S
Lines of Flux
Flux Density =
# of Flux Lines / per unit area
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POWER SYSTEMS SALES TRAINING
Magnetic Poles
S NS N
Unlike Poles Attract
Like Poles Repel
N SS N
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POWER SYSTEMS SALES TRAINING
Current Carrying Conductor
Lines of Flux
Conductor
Current Flow
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POWER SYSTEMS SALES TRAINING
Electromagnetic Coil
Lines of Flux
Flux Density
Dependant on:
Current
# of CoilsCore Material
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POWER SYSTEMS SALES TRAINING
Electo-magnetic Coils
Direction of Current determines Magnetic Polarity
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POWER SYSTEMS SALES TRAINING
Stator Windings
Electromagnetic Coils(Motor Windings)
Core
Stator
B2
A1
C2
B1
A2
C1
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POWER SYSTEMS SALES TRAINING
3 Phase AC PowerPhase - defines the type of electrical power
being supplied to the motorFrequency - defines how many times a second AC
changes direction: from positive to negative
Note: US Standard = 60 cycles per second (60 Hz)
Voltage - defines the amplitude of electric power
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POWER SYSTEMS SALES TRAINING
3 Phase AC Power
Each phase is displace 120
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POWER SYSTEMS SALES TRAINING
AC Motor Rotor
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POWER SYSTEMS SALES TRAINING
Synchronous Speed
F is Applied Frequency
P is Number of Poles per Phase
RPM =
120 x F
P
Synchronous Speed - The speed of the stators magneticfield rotation
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POWER SYSTEMS SALES TRAINING
AC Motor Basics
Rotating Magnetic Field of a 2 Pole AC Induction Motor
Motor RPM is equal to:
120 * Frequency
# Motor Poles
2 Pole Motor
Note that Frequency
is the only variable toaffect motor speed
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POWER SYSTEMS SALES TRAINING
Synchronous Speed
Synchronous Speed (60 Hz) = 7200
# of Poles2 pole AC mo tor = 3600 rpm
4 pole AC mo tor = 1800 rpm
6 pole AC mo tor = 1200 rpm
8 po le AC moto r = 900 rpm
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POWER SYSTEMS SALES TRAINING
Parts of an AC Motor
Electro-Magnets
Stator
Rotor
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POWER SYSTEMS SALES TRAINING
Base Speed
The Speed Produced by Applying
Motor Nameplate Rated Voltage
at
Rated Frequency
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POWER SYSTEMS SALES TRAINING
Motor Slip
N
Slip Speed = Synchronous Speed Rotor Speed
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POWER SYSTEMS SALES TRAINING
AC Motor Review
In an AC motor, speed varies by:
RPM =
120F
P - Slip
Where:
F is frequency in hertz
P is the # of motor polesSlip is in RPM
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POWER SYSTEMS SALES TRAINING
AC Motor Review
Horsepower of an AC motor can
be determined by:
HP =Torque x Speed
5252
Where:
Torque is in lb-ft
Speed is in RPM5252 is a constant
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POWER SYSTEMS SALES TRAINING
Motor Classifications
NEMA A
NEMA B
NEMA C
NEMA D
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POWER SYSTEMS SALES TRAINING
Speed / Torque Curve
0
% Torque
% Speed
Maximum orBreak-Down Torque
100
200
25 50 75 100
Synchronous
Torque
150
225Pull-Up Torque
Breakaway orStarting Torque
150% Torque
Rated Torque
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