Electric Motor Presentation
Transcript of Electric Motor Presentation
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Electric Motors
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Electric Motor
Converts electricity into mechanical motion
Works by electromagnetism
Lorentz Force Law
Current flowing through a
wire produces a magneticfield (labeled M here) around
the wire.
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Simple DC Motor
Armature or rotor
Commutator
Brushes Axle
Field magnet
DC power supply
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Simple DC Motor
A magnetic field is generatedaround the armature.
The left side of the armature ispushed away from the leftmagnet and drawn toward the
right, causing rotation. When the armature becomeshorizontally aligned, thecommutator reverses thedirection of current through thecoil, reversing the magneticfield.
Momentum keeps the motormoving the right direction.
The process then repeats.
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3 Pole Motor
A motor can have any
number of poles
Most common form
Doesnt get stuck inhorizontal position
In 2 pole, always
shorts out the batterywhen the commutator
flips the field
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Examples of everyday motors
EVERYTHING!!!!!
At home:
The fan over the stove and in the microwave oven The dispose-all under the sink The blender The can opener The refrigerator- Two or three in fact:
one for the compressor, one for the fan inside the refrigerator, as well as one in the icemaker
The mixer The tape playerin the answering machine Probably even the clock on the oven The washer The dryer The electric screwdriver The vacuum cleanerand the Dustbuster mini-vac
The electric saw The electric drill The furnace blower Even in the bathroom, there's a motor in:
The fan The electric toothbrush The hair dryer The electric razor
Your car is loaded with electric motors:
Power windows (a motor in each window) Power seats (up to seven motors per seat) Fans for the heater and the radiator Windshield wipers The starter motor Electric radio antennas
Motors in all sorts of places:
YouriPod Several in the VCR Several in a CD playeror tape deck Many in a computer Most toys that move
Electric clocks The garage door opener Aquarium pumps
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Motor efficiency matters
In Industry, electric motors consume:
~680 billion kWh/year
~63% of all industrial electricity consumption
~23% of all consumption
These percentages are typically higher in
developing countries, while the motors are
typically less efficient
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How is powerlostin a motor?
Mechanical (friction and windage) losses friction in bearings and seals and power consumed by
the motor cooling fan
Magnetic (core) losses hysteresis and eddy current losses in steel
laminations of the stator and rotor
Electrical (I2R) losses Stator winding losses
Rotor conductor bar losses
Stray losses miscellaneous losses associated mainly with
electromagnetic radiation
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U.S. standard for determination
of motor efficiency: IEEE 112-B
Based on Energy Policy Act legislation
(The value of efficiency is then normally converted from a decimal fraction to a percent for convenience.)
Need for a standard:
Efficiency changes as grease breaks in
Output and input power can vary
Readings of speed, torque, volts, amperes, watts are
not steady of constant values
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Overview of motor efficiencies
The following table of results from three different
testing standards:
Test Method 15 HP 75 HP 800 HP 1500 HP
IEEE 112 B (U.S.) 87.4 90.0 95.9 95.9
IEC 34-2 (International) 89.2 92.7 95.6 96.0
JEC 37 (Japanese) 90.1 93.1 95.9 96.8
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Improving motor efficiencies
According to U.S. DOE, use of only PremiumEfficiency motors could save ~20 billion
kWh/year in the U.S.
Covers wide-range of motor specifications
680 billion kWh/year consumption by electric motors
Joint specification by:
National Electrical Manufacturers Association(NEMA )
Consortium for Energy Efficiency (CEE)
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NEMA Premium motors
Example One50 hp, 1800 rpm,460 V
Example Two25 hp, 1800 rpm,460 V
EPAct Standard NEMA Premium EPAct StandardNEMAPremium
Full Load Efficiency 93.1* 94.5 92.4 93.6
Efficiency (at 75%
load) 93.6 95.1 93.1 94.1
Demand Reduction(at 75% load)
- 0.47 kW - 0.16 kW
Meets EPAct? yes yes yes yes
Incremental MotorCost - $176 - $96
Energy Savings at75% Load (6000hrs/year)
- 2,829 kWh/y - 958 kWh/y
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Expanding the definition of motor
Solar powered nano motor
The Future
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Thank you.The end.
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Background: AC Induction Motor
This is the most commonplace motor. It has arotating stator field. The rotor has imbedded
electroconductive bars resembling a pet rodent
exercise wheel, which inspired the name, squirrel
cage. The rotating stator field induces current in the
cage creating a magnetic field which causes the rotor
to follow the stator field.
First Induction
Motor, 1888
Inventor NikolaTesla
1894 InductionMotor. Worlds
largest when
new. 65 HP
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How is efficiency determined?
IEEE 112-B (United States)
IEC IEC60034.2 (International ElectrotechnicalCommission)
JEC-37 (Japanese Electrotechnical Committee)
C-390 (Canadian Standards Association)
There are different standards in usearound the world for the
determination of motor efficiency.
They yield slightly different results.
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Whats in an efficient motor?
Same components; just more and bettermaterials and closer tolerances.
Larger wire gage Lower stator winding
loss
Longer rotor and stator Lower core
lossLower rotor bar resistance Lower rotor
loss
Smaller fan Lower windage loss
Optimized air gap size Lower stray
load loss
Better steel with thinner laminations --
Lower core loss
Optimum bearing seal/shield Lower
friction loss
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