Motors Definition and Construction

I- Definition:

An electric motor is an electrical machine that converts electrical energy into mechanical energy.

Electrical Motors

In normal motoring mode, most electric motors operate through the interaction between an electric motor's magnetic field and winding currents to generate force within the motor.

Electric motors are used to produce linear or rotary force (torque), and should be distinguished from devices such as magnetic solenoids and loudspeakers that convert electricity into motion but do not generate usable mechanical powers, which are respectively referred to as actuators and transducers.

II- Construction:

II.1- ROTOR:


In an electric motor, the moving part is the rotor which turns the shaft to deliver the mechanical power.

Rotor

The rotor usually has conductors laid into it which carry currents that interact with the magnetic field of the stator to generate the forces that turn the shaft. However, some rotors carry permanent magnets, and the stator holds the conductors. Electric motors are used to produce linear force or torque (rotary).



II.3 Stator Core

Stator Laminations

The stator is the stationary part of the motor’s electromagnetic circuit. The stator core is made up of many thin metal sheets, called laminations. Laminations are used to reduce energy loses that would result if a solid core were used.










II.2- STATOR WINDINGS

Stator laminations are stacked together forming a hollow cylinder. Coils of insulated wire are inserted into slots of the stator core. 

Stator windings 

When the assembled motor is in operation, the stator windings  are connected directly to the power source. Each grouping of  coils, together with the steel core it surrounds, becomes an  electromagnet when current is applied. Electromagnetism is  the basic principle behind motor operation.

II.3- Enclosure: 

The enclosure consists of a frame (or yoke) and two end  brackets (or bearing housings). The stator is mounted inside the frame. The enclosure protects the internal parts of the motor from  water and other environmental elements. The degree of protection depends upon the type of enclosure.  

The rotor fits inside the stator with a slight air gap separating it from the stator. There is no direct physical connection between the rotor and the stator.

The air gap has important effects, and is generally as small as possible, as a large gap has a strong negative effect on the performance of an electric motor.

  

Bearings, mounted on the shaft, support the rotor and allow it to turn. Some motors, like the one shown in the left illustration,use a fan, also mounted on the rotor shaft, to cool the motor when the shaft is rotating. 

There is several types of motors which will be discussed in future posts.