For some time now, motor and fan specialist ebm-papst has been employing a contin­uous improve­ment process in fan tech­nology. In recent years, the centrifugal fans in the RadiPac series specially designed for use in air condi­tioning and venti­lation units have been constantly opti­mized, with partic­ular emphasis on energy effi­ciency, noise reduc­tion, and handling. With the new RadiPac, it has been possible to make another deci­sive improve­ment in this successful series. The new-gener­a­tion centrifugal fans work with higher effi­ciency levels (Fig. 1).

Tracking down sound sources

In this article, learn how ebm-papst opti­mizes fans in terms of noise gener­a­tion.

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Fig. 1: The new RadiPac: The new gener­a­tion of centrifugal fans offers higher effi­ciency; this results in signif­i­cantly lower oper­ating costs. (Graphic | ebm-papst)

Fig. 2: Increase in power density in the new RadiPac compared to the prede­cessor series. (Graphic | ebm-papst)

Higher speeds ensure a higher air flow and higher pres­sures, meaning that even high-pres­sure appli­ca­tions can be covered (Fig. 2). The static pres­sure increase that can be achieved is well over 2000 Pa. In addi­tion, noise gener­a­tion has decreased further; depending on the oper­ating point, the noise level is reduced by between 3 and 7 dB(A) compared to the prede­cessor series.

Impeller: High-strength composite mate­rial, plus inno­v­a­tive geom­etry

To bring about this opti­miza­tion, the impeller plays an impor­tant role. It has been devel­oped according to the latest aero­dy­namic find­ings with its five geomet­ri­cally sophis­ti­cated impeller blades (Fig. 3). A high-strength, glass-fiber rein­forced composite mate­rial is used here. The complex shape is made possible by the injec­tion molding process used. This blade geom­etry dras­ti­cally reduces flow losses. The rounded flow contour at the blade inlet and the blade trailing edge, which tapers toward the back, contribute to this. The wavy cover plate leads to an optimal air flow rate through the impeller. The inlet ring is also made of composite mate­rial and is designed for perfect inter­ac­tion with the new impeller. The sophis­ti­cated impeller geom­etry not only reduces flow losses, but also noise gener­a­tion. When it comes to its strength, the mechan­ical design of the impeller also impresses. The edges on the intake and outlet sides are counter-curved, which increases the impeller’s stability.

Powerful motors for large fans

The popular RadiPac centrifugal fan product range is already used in many venti­lation, air condi­tioning and refrig­er­a­tion appli­ca­tions. A newly devel­oped 24 kW EC motor has once again extended the power spec­trum. The high-perfor­mance drive is installed in RadiPac sizes 710 and 800 with robust metal impeller, enabling air perfor­mances of up to 40,000 m³/h and up to 2,500 Pa to be achieved.

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High periph­eral speeds are there­fore easily possible and, depending on the impeller diam­eter, they result in corre­spond­ingly high speeds. This has been proven under harsh condi­tions in exten­sive stress and long-term tests. They can be oper­ated at maximum speed in a temper­a­ture range from -25°C to +40°C. Here, the tried-and-tested indus­trial composite mate­rial meets all the rele­vant stan­dards, and UL approval is also avail­able if required.

EC motors: Stronger, more flex­ible, and even more compact

The driving force behind the new RadiPac centrifugal fans are high-effi­ciency EC motors in the power range from 500 W to 8 kW. The inte­grated EC motors with external rotor design achieve effi­ciency levels in accor­dance with the require­ments for effi­ciency class IE5 set out in IEC/TS 60034-30-2. For reasons of system effi­ciency, the drive system consisting of motor and inte­grated power elec­tronics is indi­vid­u­ally adapted on each fan, and is opti­mized for the respec­tive oper­ating range. The newly devel­oped 8 kW drive sets new stan­dards.

The perfor­mance of the inte­grated elec­tronics has been increased again, even with its more compact dimen­sions.

The perfor­mance of the inte­grated elec­tronics has been increased again, even with its more compact dimen­sions. This makes the drive the most powerful in its class at present. Design and func­tion­ality have also been updated to the latest gener­a­tion, and upgraded to include a config­urable inter­face – including the MODBUS-RTU inter­face and inte­grated reso­nance sensor (see text in box). This reso­nance sensor measures oscil­la­tions and vibra­tions in real time. It can there­fore detect imbal­ance due to dirt, for example, and then transmit a message before the fan is damaged.

No rare-earth magnets

In EC motors with an external rotor design, the exter­nally posi­tioned rotor rotates around the inter­nally posi­tioned stator. This arrange­ment allows a higher torque to be achieved than with an internal rotor motor. As a result, rare-earth magnets can be replaced by ferrites (Image 4).

Numerous flex­ible options

To meet the require­ments of different instal­la­tion situ­a­tions, the new centrifugal fans are avail­able in a stan­dard and short version (Fig. 5). With the most powerful stan­dard types, the impeller is attached to the motor in such a way that it has no nega­tive influ­ence on aero­dy­namic effi­ciency. In the short version, the motor is immersed in the impeller. These fans are more compact and are much more effi­cient than compa­rable prede­cessor models in spite of the slightly shorter axial instal­la­tion dimen­sions in compar­ison to the stan­dard version.

Fig. 5: In the stan­dard types (left), the powerful motor is completely pulled out of the flow area. In the short version (right), the motor is immersed in the impeller. (Image | ebm-papst)

Fig. 6: The new RadiPac as a ready-to-install plug & play solu­tion in a compact support bracket for easy wall mounting. (Image | ebm-papst)

Both RadiPac versions are avail­able as a motor-impeller combi­na­tion or as a ready-to-install plug & play solu­tion in a compact support bracket for easy wall mounting (Fig. 6). The support plates have been dimen­sioned to make the best possible use of space on a Euro pallet, thereby saving trans­port costs and improving the CO₂ foot­print. A completely enclosed Flow­Grid air inlet grill is also avail­able as an option. This acts as a kind of recti­fier that reduces noise-gener­ating turbu­lence in the inflow without changing the air perfor­mance and power consump­tion. It also serves as a guard grill for the intake side. The fans are then even quieter, which bene­fits venti­lation appli­ca­tions as well as many others.

Auto­matic reso­nance detec­tion for more oper­ating reli­a­bility

Centrifugal fans are used in a wide range of appli­ca­tions. Depending on the instal­la­tion situ­a­tion, there may be reso­nance in unfore­seen speed ranges. If the fan is often oper­ated in such crit­ical ranges, the drive motors’ bearing system may be damaged, leading to fan failure. For system oper­a­tors, these vibra­tions can be measured but are not easy to suppress. In its RadiPac centrifugal fans, ebm-papst solves the problem with an auto­matic reso­nance detec­tion func­tion that mini­mizes the effect of vibra­tions.

A test start-up is carried out during commis­sioning in which the vibra­tion levels over the entire speed curve are recorded and analyzed. If exces­sive vibra­tion veloc­i­ties are detected in specific ranges, the control soft­ware auto­mat­i­cally sets itself to “fast-forward” through these speed ranges in the future (Fig 7). In this way EC centrifugal fans can be oper­ated without risk of damage. Oper­a­tors can manu­ally edit the soft­ware settings at any time and always have full control.