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How the Electric Motor works

A geat box dc motor
DC Motor

The Electric Motor is found on appliances and machines wherever there is a conversion from electrical to mechanical energy. The Motor is useful in a lot of appliances in homes and industries. While the generator converts mechanical energy into electricity, an Electric Motor does the opposite, it converts electrical energy into electrical but how does this happen? It’s time to get inside the motor and see how the electric motor works.

Electric Motors are of different types, made for specific purposes and of course where they would fit best as far as machines and electronics is concerned. It’s important to know how the different kinds of electric motors work.

How the DC Motor works
Electric Motors make use of good magnets. In magnets, like poles repel and unlike poles attract each other (that is, the North Pole of one magnet will attract the South Pole of the other and vice versa).

Parts of a DC Motor
DC motor
      Major parts of a DC Motor;
  • Commutator rings/contacts
  • Rotor (Armature coil terminals)
  • Cooling Fan
  • Axle
  • Brushes
  • Ball Bearing
  • Static Magnet

When the Rotor is connected to a DC Power Source, through the Commutator rings (connected to copper coils fitted in the armature) , an electromagnetic force is induced on the Rotor forming the North and South Poles as the electrons flow from positive to negative. When this happens, the poles formed at the copper coils will try to orient with respect to the North and South Poles on the static Magnet (in most cases, an electromagnet) resulting in continuous rotation.

You might ask yourself – “if the rotor (an electromagnet which is a result of the applied electricity), moves so as to align itself to the opposite pole of the static magnet, why doesn’t it stay at that opposite pole when it gets there?" If you look closely, you will observe spaces between the commutator contacts. They are separated, each copper coil is linked to its own contact.

Electric motor working with a magnet
DC Motor working

Here is what happens;
When electricity is applied via the brushes (+ & -), here, wires are used in place of brushes, it forms North and south Poles on a single Commutator contact connected to a copper coil. When this happens, the copper coil tries to align itself with the static magnet (called field magnet). As it moves away, it leaves the brushes (in this case wires) unto the next contact close to it. As the ‘next’ copper coil gets connected to the brushes, it also forms North and south poles and tries to align itself, that is, it moves the same way the first copper coil did. This happens (continues) rapidly and effortlessly resulting in a smooth, fast and energetic rotation.
  • You could use a compass to see how the poles are arranged.
Flux is able to go through iron about a thousand times more easily than air; this is why rotors in electric motors are always very close to the static magnet.

The DC Motor can also be of two types, depending on how the field magnet (an electromagnet) is connected to the DC source. The field coil of the electromagnet is powered from the same DC source (i.e they are connected to the same brushes) as the Commutator contacts.

Shunt Motors
When the field coil of the electromagnet is connected to the DC source in parallel, the result is a Shunt Motor. The shunt motor has low starting torque but has the ability to maintain its speed as the load increases.

Series Motors
When the field coil of the electromagnet is connected to the DC source in series, the result is a Series Motor. A series wound motor has good starting torque but its speed reduces as the load increases. 

The Universal Motor

The universal motor is an electric motor that can work with both AC and DC power sources. Understanding how the universal motor works would be simpler if you understood how the DC motor works. Picture the universal motor as an advanced form of the DC series motor that has the core layers laminated to reduce eddy current loss when an AC power source is applied.

Laminated Parts of an electric motor
Motor laminated Layers

Like other electrical appliances, the ones with electric motors come with Transformers. So when an AC power source is applied to the motor, the transformer induces an EMF and extra sparking at the brush contact. So the contact brushes of a universal motor should be made of material that won’t wear out easily.

With the knowledge of how electric motors work, it is easier to understand how lots of other appliances that use motors work. These appliances include hair dryers, washing machines, blenders, drills, mixers, saws, coffee grinders, fans, vacuum cleaners and lots more. 

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