Direct Drive Blowers
In a direct drive blower, like any direct drive mechanism, no power is wasted between the motor and the blower because there are no intermediary devices. The power is transmitted directly from the motor's drive shaft to the blower without the use of a belt and pulleys, chains, or a gearbox. Though a direct drive setup requires a special slower, larger motor for applications that need constant, very precise rotational speed, the maximum torque (twisting force) at high rotational speeds generated by regular motors is perfect for electric fans that don't need to be precise. Direct drive fans are high-speed fans operating at between 1,000 and 12,000 rpm.
Direct driven fans and blowers are found within machinery powered by motors, such as cars, boats and HVAC systems, as in direct drive exhaust fans or direct drive cooling fans. A fan can also come as a separate unit with its own motor. AC or DC motors are used to drive fans. Computer equipment cooling fans require brushless DC motors because they produce a significantly lower amount of electromagnetic interference. A fan may be mounted on one shaft of a dual-shaft motor to cool the motor itself. Axial and centrifugal fans can be direct driven or belt driven. These two fan types come in low, medium and high pressures, though centrifugal fans can generate much more pressure (about four times) at the same rotational speed and torque due to their creation of a "churning" perpendicular air flow, instead of the linear axial flow.