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What is Carbon Brush, why is it used in the motor?

In today’s post, we will know what is Carbon Brush, why do we use carbon brushes in motors. Why is carbon brush used in the motor?

What is carbon brush?

Carbon brush works to supply current to the rotor inside any motor or generator. Inside all motors, there is a stator and a rotor, the stator remains stationary in one place. Therefore it is easy to supply current to it. But the rotor is always rotating, so if we connect a wire to the rotor, then that wire will break, so we use carbon brush.
carbon brush and commutator usesThe carbon brush touches the rotor. Carbon brush does not connect directly to rotor. There is a commutator with the rotor. The commutator and carbon brush are connected. Due to the rubbing of the carbon brush with the commutator, current is supplied inside the rotor.

Definition of carbon brush

These are brush made of carbon which is used to supply current to the rotor of any dc motor or generator.

why only carbon brush used in motor

Where Carbon brush used?

Carbon brushes are used in many places. Such as in Ac motor, Ac generator and Auto transformers. We can also see it in our homes, we can also see it in the mixer, grinder of the houses. We have already told you its need, it is used to supply current inside the rotor.

Why only carbon brush used in motor?

Why only carbon brush is used in motor, why aluminum or copper not used in brush? There are many reasons to answer these question.

1. Melting point of carbon is high- The first reason for using carbon brush is that the melting point of carbon is high. The melting point of copper is much lower than carbon brushes. The melting point of copper is 1050°C. This means if copper is given heat of 1050 °C, it will melt. But the melting point of Carbon is 3500 degree Celsius.
carbon melting point and copper melting pointHere we need a material with more melting point because when the carbon brush supplies electricity then it start rubbing with the commutator. So at that time temperature of the both brush and commutator is increased. so it is necessary to have a material with a high melting point. If we use copper, it will melt. And if you use carbon brush then this will not melt easily.

2. Carbon is soft as compare to copper- Carbon is much softer than copper. Its advantage is that when the carbon touches the commutator, there is friction between them. Due to this, its possible that one of the materials gets damaged. If we use copper here instead of carbon brush, then due to the hardness of copper, the commutator gets a lot of damage.
working of carbon brush
If we use carbon brush, then the carbon brush gets more damage than the commutator. we don’t want that our commutator get damaged because the commutator is much more expensive than the carbon brush. But if the carbon brush is damaged we can bring new carbon brush, it will cost us less. Where commutator have very high price. That’s why we use carbon instead of copper.

3. Negative temperature co-efficient of resistance- Friends, carbon has a different property. When the temperature of carbon is high, its resistance decreases. As we know that when there is friction between the carbon brush and the commutator, which increase high temperature .
why we use carbon brushAnd here the special thing about carbon is that if the temperature is high, then the resistance of carbon brush will decrease further. We get a lot of benefit from this because if the resistor is less, then it is easy for the current to flow. If the current is supplied easily, then there will be no problem in running the rotor. Due to this property of carbon, we get a lot of benefits.

4. Carbon is self lubricating- Carbon itself gets lubricated. Lubricating means become more smother like we have done oiling. But there is no need to lubricate the carbon brush. We require very little maintenance of carbon brushes.

important question related to the carbon brush

Does only the carbon brush is used in motor?

Yes, friends, only carbon brush is used in motor but it is used in small motor. In the large size motor, carbon graphite brush is used.

What is the price of Carbon brushes?

The carbon brush used in the generator is available in the market for Rs 25 to 35. We get the carbon brush used in the motor in the market for 15 to 20 rupees.

How much life of carbon brush?

Carbon brush lasts from 1 year to 5-7 years. Due to rubbing with the commutator, it damage to must fast.

What is the Weight of carbon brush?

It is difficult to give a definite answer to this because the size and weight of carbon brushes varies according to the machine and requirement, yet we talk about the most commonly used normal small carbon brushes, their weight is 10 to 30 grams.


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