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Exhaust fans- what is the inner structure?

Exhaust fans are specifically designed fans which are very helpful in ventilation purposes. These are the fans which are used in the old-fashioned coolers and these are powerful. Their blades are designed to suck up or absorb the air behind them and throw them out on the front side.  The fan consists of 4 leg-like structures which helps it to be fastened by means of bolts or rivets on its external frame. The motor is encased inside a steel or aluminium cylinder protected from external environmental factors. The blades are made up of steel or hardened aluminium.

Apart from this external makeup, the inner structure of the exhaust fan is also important. In fact, it is more important than the external parts because those are the parts which make the fan do what it does at the fundamental level. If you are considering to buy an exhaust fan, knowing the inner structure will help you choose among the best exhaust fans, and will also help you in case of repair. Let us see what these inner structures are.

  • Stator: This part is enclosed inside the steel cylinder and this contains groves in which coiling is done. This is the primary coiling and this is the region where current flows in from the mains and this is the coil which gets magnetised first.
  • Rotor: This is part which is surrounded by the stator (the stator doesn’t touch the rotor at all; there is air column between the two parts). The rotor gets fixed on the rotating shaft and gets it rotating when the rotor rotates. The rotor rotates due to induced magnetism. When there is current flowing in the stator current, it gets magnetised and by electromagnetic induction there is current induced in the rotor and this magnetises it which leads to poles formation by lenz’s law and the two rotate due to the repulsion and attraction forces between these pole formation.
  • Rotating Shaft: The rotating shaft is a cylindrical shaft with groves made for tight fit for various parts that in a way latch on to it. Rotor is fixed on the rotating shaft and when the rotor rotates on passage of electricity. The rotating shaft carries the blades which rotate due to the rotation of the shaft and the air circulation takes place.
  • Brushes: The brushes are small, steel made rotation guiding devices of the fan’s motor. These are enclosed by a cap each bolted or riveted to the front and back cover of the steel cylinder enclosing the stator. Inside this cap there is a strong spring which keeps the brushes in their place and stops them from getting misaligned which would lead to the decrease in the speed of the exhaust fan and can also be the cause of noise from the fan. Below the spring there is a layer of sponge which is totally soaked up in oil. The main function this sponge is to provide oil for lubrication while the rotating shaft and the brushes are in contact and the fan is working. Due to this the friction inside the fan between the brushes and the rotating shaft is decreased.
  • Wires: The wires coming out are the pathway to provide electrical energy to the motor and these are connected to the main current supply wire.

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