Mechanical Engineering: 11/18/11

Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force. The reverse process, producing electrical energy from mechanical energy, is done by generators such as an alternator or a dynamo; some electric motors can also be used as generators, for example, a traction motor on a vehicle may perform both tasks. Electric motors and generators are commonly referred to as electric machines.

Electric motors are found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives. They may be powered bydirect current, e.g., a battery powered portable device or motor vehicle, or by alternating currentfrom a central electrical distribution grid or inverter. The smallest motors may be found in electric wristwatches. Medium-size motors of highly standardized dimensions and characteristics provide convenient mechanical power for industrial uses. The very largest electric motors are used for propulsion of ships, pipeline compressors, and water pumps with ratings in the millions of watts. Electric motors may be classified by the source of electric power, by their internal construction, by their application, or by the type of motion they give.

The physical principle of production of mechanical force by the interactions of an electric current and a magnetic field was known as early as 1821. Electric motors of increasing efficiency were constructed throughout the 19th century, but commercial exploitation of electric motors on a large scale required efficient electrical generators and electrical distribution networks.

Some devices convert electricity into motion but do not generate usable mechanical power as a primary objective and so are not generally referred to as electric motors. For example, magnetic solenoids and loudspeakers are usually described as actuators and transducers,^[1]respectively, instead of motors. Some electric motors are used to produce torque or force.^[2]

This document is meant to provide all of the basic information needed by graduate students in Mechanical Engineering. It consists of the rules and procedures of the Mechanical Engineering Department, along with those of the Graduate School as found in the Graduate Catalog. If the answer to a question cannot be obtained from the the Graduate Catalog or these notes, the answer should be sought by asking: your major professor, the Chair of the Mechanical Engineering Graduate Program, or the Graduate School, preferably in that order. Our intention is to provide you with information which will be helpful in your graduate studies. Note: The Graduate School has authority to change our policies and procedures.

Additional information on graduate study can be found on the websites of the University, the Graduate School, and the ME Department.