Explain How An Electric Motor Works | Stator and Drum Anchor


Explain How An Electric Motor Works

In simple words, an electric motor or e-motor is an electromechanical converter that generates mechanical power from electrical power. As a result, electric motors have a power connection to which electrical energy is supplied. 

The mechanical output, designed as a shaft in the simplest case, rotates and acts as a drive for machines and equipment. The working principle of electric motors is based on the magnetic effect of electric current. 


How does an electric motor work?

An electric motor uses the fact that magnets affect each other depending on how they are aligned. Similar magnetic poles repel and dissimilar magnetic poles attract each other. 

To be able to make an electric motor, a permanent magnet of a certain design (1) is first required. A rotatable iron part (2) is placed between the poles of a permanent magnet, around which a coil of insulated copper wire (3) is wound. 

When a direct current flows through the coil, the coil produces a magnetic field and the iron core becomes an electromagnet. Since the electromagnet is rotated, it will now align itself such that the unequal poles of the two magnets are always facing each other. 

As long as the current is not turned off, the electromagnet remains in this position as it is held in this position by the magnetic forces. 

However, so that the electromagnet continues to rotate, the polarity of the magnetic alignment must be reversed. It does this by simply changing the direction of the current in the coil. This work is done by a slip ring (collector) connected to the coil and to which two contacts with supply voltage are applied. 

Shortly before the optimal alignment of the electromagnet is reached, the current through the slip ring is turned off and on again immediately with the opposite polarity. 

With the opposite current direction, the electromagnet’s magnetic field also reverses. Now the same magnetic poles are facing each other, which repel each other with all their force. 

The armature continues to rotate until the dissimilar magnetic poles attract each other again after a quarter turn. Shortly before optimal alignment, the polarity of the current reverses and the process begins again. 

Explain How An Electric Motor Works

What is a stator in an electric motor? 

The word stator is derived from the Latin word “stare” for resting, the stationary part of an electric motor is called the stator or stand. 

The stator can be made of either a permanent magnet or an electromagnet. In the case of the internal rotor, the stator is firmly attached to the external motor housing, in the case of an external rotor, the stator is located inside the motor. 


Explain How An Electric Motor Works

What is Drum Anchor? 

An electric motor with only a 2-pole armature would have a decisive disadvantage. In which case the polarity of the coil is reversed, the contacts of the slip ring have no connection with the coil.

When the power supply is turned off, however, 2-pole motors remain exactly in this state. The reason for this lies in the residual magnetism of the armature. 

If the power supply is turned on again, the motor may not start. That is why in practice rotors with three or more poles are used. These anchors are also known as drum anchors. 

Irrespective of the position of the armature, as the voltage is turned on, current flows through the armature coil. The engine thus starts reliably. 



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