The world without an electronic motor is simple, not imaginable. Whether they are installed with their small version (such as tiny motors found in some type of watches) up to a million-plus horsepower that is found in ships and planes and dozens of others applications. An electric motor is a device that creates electrical energy to a kinetic energy. It can work both on alternating current or direct current, where some models can work on both electricity. In this article, we will go through the most popular types of AC electric motors that are used by the majority today.
These types of AC electric motors is a most used type and it has many commercial and industrial uses. However, this motor has different variants and it is divided into 2 categories: Squirrel Cage Motor and Wound Rotor Motor. This induction motor uses the electromagnetic induction to create rotation in the rotating device which is called the shaft. If the frequency of the motor is lower then the rotor will turn slowly while the induced current which creates magnetic field and protects the rotor from the motor.
Another popular type is a single phase induction motors. The appliance of this motor is usually in areas where there is not 3-phase power such as residential, agricultural or commercial applications. Additionally, it is used for tasks that need power less than 1 horsepower. The single phase induction motor has a couple of sub-categories: Shaded pole, Capacitor run and start, Split phase and Universal motors.
A feature that is shared between all AC electric motors is the rotating field, which is created by the stator windings and can apply for three motors where each coil has its own connections with one phase of three phase electricity. While the current passes through every coil, every coil has its own sinusoidally as time passes, meaning that the current from each coil runs one-third faster than the neighbour coil. The rotor will create the torque and the magnetic field can go either clockwise or counter-clockwise. In essence, this hugely depends on the order of phases connections to the motor.
To be sure and have always a good performance, there should be a regular maintenance done every couple of months. The efficiency of the motors are crucial, so never forget to keep it in top working conditions. There are a lot of retailers on the market in Australia, that offer you a good AC electrical motors. Is up to you to contact them and see what specifications they offer whether it is going to match your needs or not.
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The majority of industrial motors are three-phase AC induction motors due to its reliability and low cost.
In this case, the electric current in the stator winding generates a rotating magnetic field that "induces" (hence the name) electric current in the rotor. The current induced in the rotor create a magnetic field that reacts against the stator field, generating rotation in the rotor. An induction motor has to operate at a slightly lower than synchronus speed, given that rotation at synchronus speed would result in no induced rotor current.
This is why induction motors are called asynchronous, because the rotor rotates slower than the stator's rotating magnetic field to produce torque about the output shaft.
If the rotor is rotating faster than the stator's rotating magnetic field, current will be induced in the stator. In this scenario, induction motors can act as generators.
Induction motors are inexpensive because they only require electromagnets in the stator and rotor to operate. They are also reliable because they do not need commutators to transmit current to the rotor, mitigating the possibility of arcing and frictional wear.
Most industrial facilities use induction motors due to their desirable characteristics such as reliability, simplicity, and affordability.
Squirrel-Cage Induction Motor (Wikipedia)
For synchronous motors the rotation of the shaft is synchronized with the frequency of the current supplied to the motor. The stator of the motor contains electromagnets that create a magnetic field, which rotates according to the characteristics of the current applied to it. The rotor contains permanent magnets or electromagnets that react against the magnetic field generated in the rotor, generating rotation of the shaft. The rotor requires a physical connection to electric power by the means of a commutator, usually consisting a conductive brush that can wear out from use.
These motors are called synchronous because the rotor rotates at the same speed as the stator's rotating magnetic field.
Although less commonly used due to higher cost, AC synchronous motors exhibit higher power efficiency than AC induction motors.
AC synchronous motors are unique in the fact that they can be used to correct the power factor of an industrial facility.
Synchronous Motor Magnetic Field Vectors (Wikipedia)
DC motors are the least commonly used type of motor, succeeded by the advent of modern AC motors.
The stator produces a static magnetic field while the rotor produces a rotating magnetic field powered by a commutator.
As a result, the rotor's magnetic field attempts to align with the stator's magnetic field which produces torque about the output shaft.
Rather than utilizing electromagnets to produce a static magnetic field, permanent magnet DC motors use magnets to create the field. Since the magnetic field is always present regardless of the motor's power state, permanent magnet motors may attract other nearby ferromagnetic materials, creating a potential risk in an industrial setting.
Permanent magnet DC motors are also heavier and bulkier due to the use of magnets in the stator.
Animation of an Operating DC Motor (Wikipedia)