How Motors Work

How Motors Work

History of Motors

Types of Motors

Frequently asked Questions


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After reflecting upon the brief history of motors, we can shift our focus to its operations. How do motors work? It helps to understand that the basic principle of electric motor is based upon electromagnetic induction. To put it simply, motors use electromagnetic fields to generate motion. Electric motors function on the principle of magnetism— like poles repel, and opposite poles attract. The direction of current flow can be changed in one of two ways.

Magnets and magnetism is the base for any motor to work. At large motors are of two types- DC and AC. In a basic DC motor, there is a fixed magnet on the outside called the field magnet and inside lies an armature that carries current. As soon as the current passes through the wired armature, it turns into an electromagnet with opposite polarity as of the field magnet. This repulsion causes the armature to rotate.

So, we need to create a perpetual opposing magnetic field between the axel and the field magnet. Generally the armature is nothing but a piece of a good conductor with copper wire coiled over it. When current passes through the armature, it turns into an electromagnet and the repulsion causes it to rotate. Here, we reach a situation where after half rotation the electromagnet gets stuck as the opposite poles attract each other. To overcome this, one would need to flip the current in order to obtain perpetual opposite magnetic poles. This is achieved with use of commutator and brushes.

Commutator is attached to the axle of the electromagnet, so that they spin along with the magnet. The brushes are just two pieces of springy metal or carbon that make contact with the contacts of the commutator. The key is that as soon as the armature passes over the maximum flux of the field magnet, the poles of the electromagnet must flip. Because of the flip, the North Pole of the electromagnet is always in line with North Pole of field magnet that keeps the armature under constant repulsion. Up till now, we have been talking about bipolar motors. These motors can get stuck if after halting, the commutators are not in contact with the brushes. This demanded more than two poles in an armature and the motors henceforth should have many poles to suit various power and RPM requirements.

The AC motors on the other hand have the advantage of auto-change of polarity due to alternating current. The electric motors run smoothly at the frequency of the sine wave and are also called synchronous motor. Most common AC motors are induction type. This means that no current passes through the armature coils and electric current is induced in the rotating coils rather than being supplied to them directly. An induction motor must achieve a rotating magnetic field to continue to exert a torque on the armature coils, while extra coils on the pole pieces achieve the rotating field.

This explains the way motors work and the cause of rotation. Based upon these basic principle, the motors have evolved and come a long way. The modern-day motors are much lighter, cost-efficient and productive. Right from microwave ovens, furnace blowers, fans, screwdrivers to radio antennas—motors are used almost everywhere.

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