Electrical Energy Equipment: Electric Motors
Energy Efficiency Guide for Industry in Asia – www.energyefficiencyasia.org
©UNEP
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ELECTRIC MOTORS
1. INTRODUCTION..........................................................................................................1
2. TYPES OF ELECTRIC MOTORS.........................................................................2
3. ASSESSMENT OF ELECTRIC MOTORS.......................................................10
4. ENERGY EFFICIENCY OPPORTUNITIES...................................................14
5. OPTION CHECKLIST..............................................................................................21
6. WORKSHEETS ...........................................................................................................22
7. REFERENCES .............................................................................................................24
1. INTRODUCTION
This section describes the main features of the electric motors.
1.1 Where motors are used
An electric motor is an electromechanical device that converts electrical energy to
mechanical energy. This mechanical energy is used for, for example, rotating a pump
impeller, fan or blower, driving a compressor, lifting materials etc. Electric motors are used at
home (mixer, drill, fan) and in industry. Electric motors are sometimes called the “work
horses” of industry because it is estimated that motors use about 70% of the total electrical
load in industry.
1.2 How a motor works
The general working mechanism is the same for all motors (Figure 1):
An electric current in a magnetic field will experience a force.
If the current carrying wire is bent into a loop, then the two sides of the loop, which are
at right angle to the magnetic field, will experience forces in opposite directions.
The pair of forces creates a turning torque to rotate the coil.
Practical motors have several loops on an armature to provide a more uniform torque
and the ma