What is an Induction Motor?

An Induction Motor is an electric motor that transforms electrical energy into mechanical energy via electromagnetic induction. Induction motors account for the vast majority of electric motors and can be found in a large range of industrial, commercial and residential applications. The "induction" part of the name refers to the fact that the rotor of the motor runs with no physical connection with the stator and it is always slightly slower than the rotating magnetic field of the stator (referred to as "slip"). Induction motors are quite simple and relatively inexpensive to make and maintain.

Principle of Operation of the Induction Motor

The principle of operation of an induction motor is based on Faraday's Law of electromagnetic induction. When alternating current passes through the stator winding of the motor, a rotating magnetic field is established. This rotating magnetic field induces a current in the rotor, causing it to turn. The rotor of the motor attempts to "catch up" with the rotating magnetic field established by the stator; however, it is always going to run slightly slower than the stator (the term for this is "slip"). The ability of induction motors to operate with slip is one of the characteristics of the motor that enables it to operate efficiently.

Types of Induction Motors

Squirrel Cage Induction Motor

The squirrel cage induction motor is the most common type of induction motor. The rotor is made up of conductive bars in a cage structure which is simple, rugged, and reliable. These motors are commonly used for fans, pumps, compressors, conveyor belts, etc. Their simplicity is in part the reason they are maintained readily and replacement motors tend to be in stock for rapid delivery.

Wound Rotor Induction Motor

The wound rotor induction motor contains coils wound on the rotor and connected to external circuits using slip rings. Wound rotor motors are ideal for applications that require high starting torque or for speed control applications. Wound rotor motors offer the ability to control the current flowing in the rotor's coils from an external source to accomplish different starting characteristics.

Advantages of Induction Motors

Simple Construction and Easy Maintenance

Generally, the construction of the induction motor is quite simple and has few moving parts (Other than wound rotor, induciton motors have no brushes or slip rings) for ease of maintenance and to help with reliability in longer term operation.

Low Cost

Induction motors are lower priced than other motor types which need to be considered for many of its applications.

High Reliability and Durability

Squirrel cage induction motors are particularly reliable and durable because they contain few, if any, sliding parts (with the exception of wound rotor motors), and are designed for operation over extended periods of time in harsh environments.

Good Overload Characteristic

Squirrel cage induction motors have excellent overload characteristics and handle varying loads quite well, thus making them suitable for variable load applications.

Applications of Induction Motors

Industrial Manufacturing

Induction motors are commonly used in industrial manufacturing applications; pumps, fans, compressors, conveyors, in industrial applications are common uses for induction motors because they are reliable and cost-effective.

Home Appliances

Induction motors are also common in the home appliance industry; this is evident by the use of induction motors in fans, washing machines, air conditioners, refrigerators, and the like. Home appliances must be reliable and cost-effective to increase consumer demand.

Transportation

A more common use of induction motors is in the transportation industry (trains, subways, elevators, etc.). Induction motors are ideal because they are stable and efficient.  

Power Industry

Induction motors are very widely used in the power industry. Common uses for induction motors in the power industry are found in water pumps, wind turbines, and other forms of power generation, where longevity and durability with high overload characteristics are valued.

The Future of Induction Motors

The technology of induction motors will continue to develop as manufacturing becomes smarter, processes become more automated, and renewable energy solutions are continuously sought.