AC Motor Construction

 commonly used in industrial applications. This type of motor has three main parts, rotor, stator, and enclosure. The stator and rotor do the work, and the enclosure protects the stator and rotor.



Stator Core
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.



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



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.



Rotor Construction 
The rotor is the rotating part of the motor’s electromagnetic circuit. The most common type of rotor used in a three-phase induction motor is a squirrel cage rotor. Other types of rotor construction is discussed later in the course. The squirrel cage rotor is so called because its construction is reminiscent of the rotating exercise wheels found in some pet cages.



A squirrel cage rotor core is made by stacking thin steel laminations to form a cylinder.



Rather than using coils of wire as conductors, conductor bars are die cast into the slots evenly spaced around the cylinder. Most squirrel cage rotors are made by die casting aluminum to form the conductor bars. Siemens also makes motors with die cast copper rotor conductors. These motor exceed NEMA Premium efficiency standards.

After die casting, rotor conductor bars are mechanically and electrically connected with end rings. The rotor is then pressed onto a steel shaft to form a rotor assembly.


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

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

AC MOTOR

AIRCOOLED BRUSHLESS DC MOTOR

A SIMPLE DC MOTOR

DC MOTOR FROM GATORAD BOTTLE

SIMPLE DC MOTOR

ELECTRIC COOKING TIME

ELECTRIC MOTORS INFIRMATION

You can't get much simpler than the Beakman motor shown below.  One battery, one magnet and one piece of wire formed into a coil which rotates in another piece of wire (a paper clip) held onto the battery at each end by a rubber band.  It works, but apart from demonstrating the principle that electricity and magnets can be used to produce motion, it's not very practical.

Electric motors are everywhere! In your house, almost every mechanical movement that you see around you is caused by an AC or DC electric motor. By understanding how a motor works you can learn a lot about magnets, electromagnets and electricity in general. On this page we hope you will learn what makes an electric motor spin.

An electric motor is all about magnets and magnetism.  A motor uses magnets to create motion.  If you have ever played with magnets you know the law of magnets: Opposites poles attract and like poles repel.  So if you have two bar magnets with their ends marked "north" and "south," then the north end of one magnet will attract the south end of the other. On the other hand, the north end of one magnet will repel the north end of the other.  Inside an electric motor, these attracting and repelling forces create rotational motion.

The armature (or rotor) is an electromagnet.  Like the Beakman rotor above made of copper wound in a circle, the motor below has copper wound around a soft iron core.  The field magnet is still a permanent magnet, only this time there are two semi-circular magnets fitted inside a steel casing.  In some larger motors and generators the field magnet could also be an electromagnet.  In smaller motors it usually isn't to save the electricity that would otherwise be needed to make magnetism and also to reduce complexity.  Actually, these days there are quite a few large motors using magnets to drive cars and the like.  The Solar Navigator catamaran uses permanent magnet motors that are very efficient.

    

             Armature          Casing and magnets     Brush housing   

    Motor assembly   

                            

The motor we have dismantled above is a simple electric toy motor.  Millions of these motors are made every year by Mabuchi and other famous producers.  Mabuchi motors were used on the early 1/10th and 1/20th development models of Solar Navigator.

If you take apart a small electric motor, you will find that it contains the same pieces described above: two small permanent magnets inside casing, two brushes held in a housing, and an electromagnet made by winding wire around pieces of shaped metal (laminations) on a steel shaft, known as an armature or rotor. Almost always the rotor will have three poles or more. There are two good reasons for a motor to have three poles or more:

1. It causes the motor to have better dynamics (movement). In a two-pole motor, if the electromagnet is at the balance point, perfectly horizontal between the two poles of the field magnet when the motor starts, you can imagine the armature getting "stuck" there. That never happens in a three-pole motor, which can start turning from any starting position.
2. Each time the commutator hits the point where it flips the field in a two-pole motor, the commutator shorts out the battery (directly connects the positive and negative terminals) for a moment. This shorting wastes energy and drains the battery needlessly. A three-pole motor solves this problem as well.  In fact the timing of an efficient motor switches on the armature at a point when the magnetic repulsion is strongest.

It is possible to have any number of poles, depending on the size of the motor and the specific application it is being used in. Also, motors come in different shapes and sizes to fit almost anywhere.  Special, very powerful (rare earth) permanent magnets can be used to boost power - although this increases the cost.  Special brush materials can be used to improve power handling. And these days, instead of using a mechanical switch like the commutator, electronics can be used instead to get very accurate timing and sometimes exotic sine waves.  This also eliminates sparking and brush wear problems, so reducing servicing.

Other efficient dc designs do not have a conventional iron armature, but an ironless copper winding (a wire cylinder) very close to a permanent magnet, such as in the Swiss Maxon design motors, also used on Solar Navigator development models.

Motor turning

Electrical motor picture

Electric Motor

AC Three-Phase Motors AC Single-Phase Motors Brake Motors Two-Speed Motors Geared Motors Submersible Pumps Centrifugal Pumps Lawnmower Motors Swimming Pool Motors	Diagram of an Electric Motor
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important picture

Electrical Engineer Career

• A project engineer career can cover a wide range of disciplines in engineering, ranging from civil to electrical engineering. The average length of a professionalengineer’s career is over 40 years and during this time, engineers can have many roles, including project engineer.
• A test engineer of this type might be referred to as a software engineer, hardware engineer, quality assurance lead, or test technician. Another position in the world of test engineer careers is that of the electrical test engineer. This type of engineer will focus mainly on the ways in which wiring components are arranged and function together.

Electrical Engineer

An electrical engineer has many potential job functions but most work on designing products that are powered by or produce electricity. Sometimes, an electrical engineer will dedicate his or her time to a single electrical product. While there are millions of potential products an electrical engineer may work on, some examples include medical technology, cellular phones, handheld gaming systems, and airline navigation systemWhen beginning a project, an electrical engineer usually starts by figuring out the purpose of the product. He or she will then plan the circuitry and wiring of the electronic components. A prototype is generally built on which extensive tests are conducted in order to make sure the plans work as designed, and that all of the components work well together. An electrical engineer might also test broken products in order to find out where they went wrong and how the design can be altered to prevent its recurrence. He or she might be responsible for examining existing products that have no known or significant problems simply to uncover whether they can be improved.s.