What are Motorized Impellers?

An impeller is a type of rotor that is often implemented in compressors and pumps in order to increase the pressure and flow of a fluid. Motorized impellers in particular are fan impellers which are fixed to the rotor of an external rotor motor, meaning that they can operate with lower bearing loads and minimal vibration. Motorized impellers also have the ability to serve as a rotating heat sink, ensuring that heat is well dissipated for optimal cooling. With the combination of multiple roles into a single assembly, a motorized impeller serves as an advantageous device for applications in which space is a concern.

While different motors can widely vary in their shape and size, the biggest difference in style is whether the device features an internal or external rotor configuration. The internal rotor style is the most common, and it consists of a stator that is fixed to the motor housing. The rotor is situated within the stator, and it transmits torque through the output shaft which is connected to the fan impeller. External rotors are fairly similar in their parts, though their orientation is opposite. With such variations, the stator rotates inside the rotor, thus there is no need for an output shaft. This can also be beneficial as it allows the assembly to be smaller in size while permitting direct attachment of the fan impeller to the external rotor to create a motorized impeller.

During operations, the internal rotor motor will be governed by set and standard speed ratings alongside incremental power levels. With external rotor motors that are used for motorized impeller assemblies on the other hand, the motor is specifically designed to accommodate the particular impeller they are used for. These motor operating characteristics are very beneficial as they create more efficiency due to their ability to meet a wider range of power and speed ratings. There are also a number of ranges at which motorized impellers operate at, though the common ranges are 25 W to 7,000 W and 1,000 RPM to 4,000 RPM.

Beyond variations existing for the motor components, there are also a few impeller designs that may be used depending on the need of the application. Centrifugal fan impellers are one of the most common variations, and they often utilize backward curved blades which are capable of producing sufficient static pressure for high efficiency operations. Airfoil blades are a more powerful blade option, and they provide an assembly with increased performance. For centrifugal impellers in particular, inlet cones are not recommended.

Axial motorized impellers are the other common design, and they are used when there are high amounts of fluids that need to be moved with low static pressure. As such, axial impellers are mostly reserved for non-ducting applications in which high airflow is a requirement or desire. Like centrifugal design, the highest efficiency and performance is achievable with airfoil blades. Depending on the need, the most popular housings for motorized axial impellers are panels and guard-mounts.