Electric Motors

1
Electric Motors

• ESM 288
• Betty Seto
• Kat Wuelfing

2
Electric Motor

• Converts electricity into mechanical motion
• Works by electromagnetism
• Lorentz Force Law

Current flowing through a wire produces a
magnetic field (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 generated around the
  armature.
• The left side of the armature is pushed away from
  the left magnet and drawn toward the right,
  causing rotation.
• When the armature becomes horizontally aligned,
  the commutator reverses the direction of current
  through the coil, reversing the magnetic field.
• Momentum keeps the motor moving the right
  direction.
• The process then repeats.

5
3 Pole Motor

• A motor can have any number of poles
• Most common form
• Doesnt get stuck in horizontal position
• In 2 pole, always shorts out the battery when the
  commutator flips the field

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Examples of everyday motors

• 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 player in the answering machine
• Probably even the clock on the oven
• The washer
• The dryer
• The electric screwdriver
• The vacuum cleaner and the Dustbuster mini-vac
• The electric saw
• The electric drill

• 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
• Your iPod
• Several in the VCR
• Several in a CD player or tape deck
• Many in a computer
• Most toys that move
• Electric clocks
• The garage door opener
• Aquarium pumps

• EVERYTHING!!!!!

7
Motor efficiency matters

• In U.S. Industry, electric motors consume
• 680 billion kWh/year
• 63 of all industrial electricity consumption
• 23 of all U.S. consumption

• These percentages are typically higher in
  developing countries, while the motors are
  typically less efficient

Source U.S. DOE. Energy Efficiency and
Renewable Energy (EERE). www.pumps.org/public/memb
er_services/presentations/2005_spring/electric_mot
or_efficiency.pps
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How is power lost in 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

Source U.S. DOE. Energy Efficiency and
Renewable Energy (EERE). www.pumps.org/public/memb
er_services/presentations/2005_spring/electric_mot
or_efficiency.pps
9
U.S. standard for determination of motor
efficiency IEEE 112-B

• Based on Energy Policy Act legislation

• 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

                                                
                                                  
                       (The value of efficiency
is then normally converted from a decimal
fraction to a percent for convenience.)
Source http//www.iprocessmart.com/leeson/leeson_
epact_motor_testing.htm
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Overview of motor efficiencies

• The following table of results from three
  different testing standards

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Improving motor efficiencies

• According to U.S. DOE, use of only Premium
  Efficiency 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
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The Future

• Expanding the definition of motor
• Solar powered nano motor

http//www.spacemart.com/reports/Nano_World_First_
Solar_Powered_Nano_Motor.html
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Thank you.The end.
15
Background AC Induction Motor

• This is the most commonplace motor. It has a
  rotating 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 Nikola Tesla
1894 Induction Motor. Worlds largest when new.
65 HP
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How is efficiency determined?
There are different standards in use around the
world for the determination of motor efficiency.
They yield slightly different results.

• IEEE 112-B (United States)
• IEC IEC60034.2 (International Electrotechnical
  Commission)
• JEC-37 (Japanese Electrotechnical Committee)
• C-390 (Canadian Standards Association)

Source U.S. DOE. Energy Efficiency and
Renewable Energy (EERE). www.pumps.org/public/memb
er_services/presentations/2005_spring/electric_mot
or_efficiency.pps
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Whats in an efficient motor?

• Same components just more and better materials
  and closer tolerances.
• Larger wire gage Lower stator winding loss
• Longer rotor and stator Lower core loss
• Lower 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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A Useful Tool MotorMaster

• Compare
• Motors of varying eff.
• Repair vs. replace
• gt25,000 motors in database
• Calculate energy savings
• Calculate LCC

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A New Tool MotorMaster International

• Includes IEC motors
• English, Spanish, French modes
• Accomodates several currencies