An electric motor is an apparatus used to convert electrical energy to mechanical energy. Michael Faraday in 1821 first demonstrated this device. It works through the interaction between magnetic fields and current carrying conductors. The reverse process is carried out using a generator or a dynamo. Electric motors have a diverse applicability which includes its usage in industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives. The motors can be powered by either direct or alternating current. While the use of medium sized motors are confined to industries, the large ones are put to use for propulsion of large ships and as pipeline compressors, with rating in the millions of watts.
Electric motors are classified according to the current flowing in the conductors, i.e. direct current (DC) and alternating current (AC). A DC motor is further classified into four types :
- DC series wound motor
- DC shunt wound motor
- DC compound motor - there are also two types:
- cumulative compound
- differentially compounded
- Permanent Magnet DC Motor.
A conventional AC motor consists of the following two parts:
- An outside stationary stator having coils supplied with AC current to produce a rotating magnetic field, and;
- An inside rotor attached to the output shaft that is given a torque by the rotating field.
Nowadays there is a constant deprivation of raw materials used. Rare earth minerals used in the fabrication of direct current electric motors are mainly concentrated in and around China. AC motors typically use conventional copper wire for their stator coils and copper or aluminum rods or bars for their rotor.
The initial DC motors ran upto 600 revolutions per minute and were used to power machine tools and printing press. However, the highly expensive zinc electrodes made the motors commercially unsuccessful. Nonetheless, 20th century saw a revolution in electric motors, since every machine was equipped with its own motor instead of conforming to the archaic industrial processes. It also started being used in agricultural spheres for handling grain and pumping water, and also in common households.
Used in most modern machines electric motors are most popular in robotics. From food processors and grinders to locomotives and conveyor belts, the use of electric motors is crucial for the survival of mankind in today’s world. Without electric motors, which are used so extensively today, mankind would not have been able to achieve the technological prowess that it owns today.
