Fans generate noise from the rapid flow of air around blades and obstacles, and sometimes from the motor. Fan noise has been found to be roughly proportional to the fifth power of fan speed; halving speed reduces noise by about 15dB.[11]
Fan drive methods[edit source | editbeta]
Building heating and cooling systems commonly use a squirrel cage fan driven by belt from a separate electric motor.
Internal combustion engines sometimes drive an engine cooling fan directly, or may use a separate electric motor.
Large electric motors may have a cooling fan either on the back or inside the case. (Shown with black rear cover removed.)
Dual shaft fan motor in a window air conditioner.
Standalone fans are usually powered by electric motors, often attached directly to the motor's output with no gears or belts. The motor is either hidden in the fan's center hub or extends behind it. For big industrial fans, three-phase asynchronous motors are commonly used, placed near the fan and driving it through a belt and pulleys. Smaller fans are often powered by shaded pole AC motors, or brushed or brushless DC motors. AC-powered fans usually use mains voltage, while DC-powered fans use low voltage, typically 24, 12, or 5 V. Cooling fans for computer equipment always use brushless DC motors, which generate much less electromagnetic interference than other types.
In machines with a rotating part, the fan is often connected to it rather than being powered separately. This is commonly seen in motor vehicles with internal combustion engines, where the fan is connected to the drive shaft directly or through a belt and pulleys.
A common configuration is a dual-shaft motor, where one end of the shaft drives a mechanism, while the other has a fan mounted on it to cool the motor itself. Window air conditioners commonly use a dual-shaft fan to operate separate blowers for the interior and exterior parts of the device.
Where electrical power or rotating parts are not available, fans may be drive by other methods. High-pressure gases such as steam can be used to drive a small turbine, and high-pressure liquids can be used to drive a pelton wheel, which can provide the rotational drive for a fan.
Large, slow-moving energy sources such as a flowing river can also power a fan using a water wheel and a train of gears or pulleys.
Fan drive methods[edit source | editbeta]
Building heating and cooling systems commonly use a squirrel cage fan driven by belt from a separate electric motor.
Internal combustion engines sometimes drive an engine cooling fan directly, or may use a separate electric motor.
Large electric motors may have a cooling fan either on the back or inside the case. (Shown with black rear cover removed.)
Dual shaft fan motor in a window air conditioner.
Standalone fans are usually powered by electric motors, often attached directly to the motor's output with no gears or belts. The motor is either hidden in the fan's center hub or extends behind it. For big industrial fans, three-phase asynchronous motors are commonly used, placed near the fan and driving it through a belt and pulleys. Smaller fans are often powered by shaded pole AC motors, or brushed or brushless DC motors. AC-powered fans usually use mains voltage, while DC-powered fans use low voltage, typically 24, 12, or 5 V. Cooling fans for computer equipment always use brushless DC motors, which generate much less electromagnetic interference than other types.
In machines with a rotating part, the fan is often connected to it rather than being powered separately. This is commonly seen in motor vehicles with internal combustion engines, where the fan is connected to the drive shaft directly or through a belt and pulleys.
A common configuration is a dual-shaft motor, where one end of the shaft drives a mechanism, while the other has a fan mounted on it to cool the motor itself. Window air conditioners commonly use a dual-shaft fan to operate separate blowers for the interior and exterior parts of the device.
Where electrical power or rotating parts are not available, fans may be drive by other methods. High-pressure gases such as steam can be used to drive a small turbine, and high-pressure liquids can be used to drive a pelton wheel, which can provide the rotational drive for a fan.
Large, slow-moving energy sources such as a flowing river can also power a fan using a water wheel and a train of gears or pulleys.
