There are several types of electric motors, each with its own unique features and benefits. Some run at a constant speed, some have a relatively small (but not adjustable) drop in speed as the load increases, some have a large speed decline with load, and some have speed which can be adjusted over a wide range even at the same load. Some are designed to provide high starting torque such as in cranes and elevators and others can be stepped through accurate short motions (such as in computer tape drives).
This wide range of unique motor attributes can make the selection of motors difficult. Fortunately, most of us only have to contend with motor replacement since the driven equipment is usually purchased with a motor from the equipment manufacturer. And, in most cases, our only consideration is whether to repair or replace the failed motor. Replacement usually just means taking the information off the nameplate of the failed motor and calling a motor supplier. Additional guidance can often be obtained from the manufacturers of motors or consultants who specialize in the specific motor applications.
This training program only addresses the typical motors in widespread use today. These include three-phase induction and synchronous motors, single-phase motors and the two types of direct-current motors.
Two additional courses published by The Electrification Council: Motors & Motor Controls and Motors & Drives develop these topics more completely.
Insulation Systems
Torque & Horsepower
Efficiency & Power Factor
The Three-Phase Induction Motor
Major Categories Of Electric Motors
Characteristics Of Direct Current Motors
Characteristics Of A Synchronous Motor
Current Speed Characteristics Of An Induction Motor
Speed-Torque Characteristics Of An Induction Motor
