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Fan assemblies with this control input provide the ability to adjust the rotational speed of the fan without changing the input voltage delivered to the cooling fan assembly. A variable rotation speed allows the cooling rate to be adjusted to meet demand, quietening the fan and saving energy when full speed is not required.
Where noise is an issue, larger, slower-turning fans are quieter than smaller, faster fans that can move the same airflow. Fan noise has been found to be roughly proportional to the fifth power of fan speed; halving the speed reduces the noise by about 15 dB. [22] Axial fans may rotate at speeds of up to around 38,000 rpm for smaller sizes. [23]
Small variable-frequency drive Chassis of above VFD (cover removed). A variable-frequency drive (VFD, or adjustable-frequency drive, adjustable-speed drive, variable-speed drive, AC drive, micro drive, inverter drive, variable voltage variable frequency drive, or drive) is a type of AC motor drive (system incorporating a motor) that controls speed and torque by varying the frequency of the ...
Fan controllers can produce a fixed fan speed using an inline resistor or diode; or a variable speed using a potentiometer to supply a lower voltage. Fan speed can also be reduced more crudely by plugging them into the power supply's 5 volt line instead of the 12 volt line (or between the two for a potential difference of 7 volts, although this ...
A High-volume low-speed fan. A high-volume low-speed (HVLS) fan is a type of mechanical fan greater than 7 feet (2.1 m) in diameter. [1] HVLS fans are generally ceiling fans although some are pole mounted. HVLS fans move slowly and distribute large amounts of air at low rotational speed– hence the name "high volume, low speed."
The affinity laws (also known as the "Fan Laws" or "Pump Laws") for pumps/fans are used in hydraulics, hydronics and/or HVAC to express the relationship between variables involved in pump or fan performance (such as head, volumetric flow rate, shaft speed) and power. They apply to pumps, fans, and hydraulic turbines. In these rotary implements ...
AC electric motors can be run in fixed-speed operation determined by the number of stator pole pairs in the motor and the frequency of the alternating current supply. AC motors can be made for "pole changing" operation, reconnecting the stator winding to vary the number of poles so that two, sometimes three, speeds are obtained.
Direct torque control (DTC) is one method used in variable-frequency drives to control the torque (and thus finally the speed) of three-phase AC electric motors.This involves calculating an estimate of the motor's magnetic flux and torque based on the measured voltage and current of the motor.