Fan Drive Methods

Whenever possible, the fan wheel should be directly connected to the motor shaft. This can usually be performed with a small centrifugal fans and with a propeller fans up to 60 C. in diameter. The deflection and the critical speed shaft, however, should be investigated to determine whether it is safe.

When choosing a motor to drive the fan, it is desirable to choose a standard engine one size larger than the fan requirements. It should be borne in mind, however, that direct connected fans do not require large margin, and that belt-driven units. It is desirable to use a belt drive when you need speed of the fan or horsepower, raises concerns as to the change pulley size is relatively cheap if a mistake is made (see Fig. 3-29).

Directly related small fans for various applications are usually driven single-phase AC motors split-phase, condenser, or shadedpole type. Capacitor engine more efficient, electrically and is used in areas where there are restrictions. These engines, however, as a rule, are run at the same speed. With such an engine, if it is necessary to vary the amount of air pressure or a fan or blower, air regulation, damper installation is usually done.

In large installations (for example, when a mechanical project need a fan), different disk methods are used:

Phase motor speed varying.
Aconstant-speed, directly connected motor, which, with the help of mobile vanes in fan inlet, serves to regulate the pressure and volume of air.

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