Drawing on its core compe­ten­cies in aero­dy­namics, motor tech­nology and elec­tronics, fan and motor specialist ebm-papst launched the RadiCal centrifugal fan series more than 10 years ago, a series that has since proven its worth in many venti­lation and air-condi­tioning systems.

Now, the Mulfingen-based company is intro­ducing a second gener­a­tion of the fans with partic­u­larly impres­sive air flow rates, along­side remark­ably compact dimen­sions and pleasant noise char­ac­ter­is­tics (Figs. 1 and 2).

The main contrib­u­tors to this have been aero­dy­namic opti­miza­tions, refined Green­Tech EC motors, and further improve­ments in control elec­tronics. An addi­tional size has also been included, making it even easier for users to find the right solu­tion.

New blade design improves aero­dy­namics

With the aid of high-perfor­mance devel­op­ment tools and produc­tion engi­neering, the first step was to opti­mize the design of the impellers in line with aero­dy­namic criteria.

In this, the devel­opers bene­fited from plastic produc­tion, which now offers design freedom in all three dimen­sions – making it possible to achieve an inno­v­a­tive blade geom­etry that helps signif­i­cantly increase effi­ciency and reduce noise.

The “twisted” blades are curved into each other and the shape of the leading and trailing edges has been completely redesigned. This improves the flow behavior (Fig. 3) while at the same time increasing the strength of the impeller, which is made of resis­tant plastic. The corru­gated impeller cover plate also improves aero­dy­namic char­ac­ter­is­tics and hence air perfor­mance.

The centrifugal module, or housing box, has also been completely redesigned. The inclined struts, for example, provide an addi­tional boost to air perfor­mance. The shape of the struts can be varied over the axial height to avoid back­flow areas as effec­tively as possible. There is also an enlarged intake diam­eter, which ensures a greater air flow rate through the impeller. With the size 190, for example, the intake diam­eter has been increased from 132 to 150 mm, which helps air throughput.

Signif­i­cant noise reduc­tion

There is further poten­tial for improve­ment in clear­ance gap losses. Finding ways to improve the air gap, in other words the distance between the inlet nozzle and the impeller, is chal­lenging because the gap will always have a certain toler­ance for manu­fac­turing reasons. In the case of the second-gener­a­tion RadiCal fans, however, new manu­fac­turing methods have made it possible to reduce the air gap signif­i­cantly, depending on the size.

As a result, there is less turbu­lence, effi­ciency increases and noise is reduced (Fig. 4). The new air inlet grille also helps to prevent noise (Fig. 5). In this further devel­op­ment, the struts were initially dimen­sioned to mini­mize losses.

As noise analysis showed that the rotor area had a major influ­ence on noise devel­op­ment, a cap was added to the center of the air inlet grille, which signif­i­cantly reduced noise in the lower frequency range. Compared with the current series version, it is up to 2 dB(A) quieter when installed in a test rig (Fig. 6).

New motor gener­a­tion

The new EC motors also contribute to noise reduc­tion. Depending on the size of the fans, they cover a power range of up to 170 W for single-phase networks. Fans for three-phase networks and outputs of up to 1.5 kW will follow at a later date. There are no disrup­tive reso­nances when there is a change in speed.

In addi­tion to good noise char­ac­ter­is­tics, the new gener­a­tion of motors also boasts excel­lent EMC char­ac­ter­is­tics and dura­bility. The commu­ta­tion and control elec­tronics are tuned to the motors and the air flow and oper­ating point can be precisely adjusted.

Control and moni­toring are possible either through 0 – 10 V/PWM or option­ally through MODBUS-RTU starting from the 170 W variant. Networking via the commu­ni­ca­tion bus then makes it possible to use the motor data for preven­tive main­te­nance measures, for example, or to quickly adapt the fans to changes in oper­ating condi­tions.

Compact and easy to inte­grate

Since no other instal­la­tion situ­a­tion is the same, the new centrifugal fans are very adapt­able. They are avail­able as a motor­ized impeller, as a centrifugal module with ready-to-install housing or with a support bracket (Fig. 7).

Three different mounting levels are provided for the compact centrifugal module. If instal­la­tion space is tight, users will appre­ciate another design detail: the back­plate is smaller than the cover plate.

As a result, the direc­tion of discharge is more in the axial direc­tion. This is an advan­tage if there is little space in the centrifugal direc­tion. The fans are also a few millime­ters shorter axially than their prede­cessor. Thanks to the high air flow rates, a smaller size can now be used compared to the prede­cessor model, depending on the oper­ating points.

The second-gener­a­tion RadiCal fans will be avail­able in the familiar sizes 175, 190, 225, 250 and 280. Size 206 is new and improves the power rating. This means that the right centrifugal fans are avail­able for effi­cient resi­den­tial venti­lation or switch cabinet cooling, not only deliv­ering high air flow rates, but also oper­ating extremely quietly.