An electric motor is an electric machine that transforms electrical energy into mechanical energy through electromagnetic interactions. Some of the electric motors are reversible, they can transform mechanical energy into electrical energy working as generators. Electric traction motors used in locomotives often perform both tasks if equipped with regenerative brakes.
They are widely used in the typical industrial gear box, commercial and private installations. They can be connected to a power supply or battery operated. Thus, in cars they are starting to be used in hybrid vehicles to take advantage of the advantages of both.
Principle of operation of DC motors
Alternating current and DC motors are based on the same operating principle, which states that if a conductor carrying an electric current is within the action of a magnetic field, it tends to move perpendicularly to the magnetic field’s lines of action.
The conductor tends to function as an electromagnet due to the electrical current circulating through it, thus acquiring magnetic properties, which, due to the interaction with the poles located in the stator, cause the circular movement observed in the motor rotor.
Starting from the fact that when current passes through a conductor it produces a magnetic field, and also if we put it within the action of a powerful magnetic field, the product of the interaction of both magnetic fields makes the conductor tends to move, thus producing mechanical energy.
This DC machine is one of the most versatile in the industry. Its easy position, stop and speed control make it one of the best options in process automation and control applications. But with the advent of electronics, their use has greatly decreased, since asynchronous AC motors can be controlled equally at prices more accessible to the average consumer in the industry. Despite this, DC motors are still used in many power (trains and trams) or precision (machines, micro motors, etc.) applications.
The main characteristic of the DC motor is the possibility to regulate the speed from idle at full load. Its main drawback, maintenance, very expensive and laborious. However, it is always a good option to consider especially in cases where it may be more convenient to opt for this type.
A DC machine (generator or motor) is composed mainly of two parts, a stator that gives mechanical support to the device and has a gap in the center usually cylindrical shape. In the stator there are also the poles, which can be permanent magnets or winding with copper wire on an iron core. The rotor is generally cylindrical in shape, also wound and with a core, to which the current comes through two brushes. DC motors are also built with permanent magnet rotor for special applications.