The results of the optimisation process are impressive, as shown by the “old” versus “new” comparison in Figs. 1 and 2. All-in-all, modification of the flow machine brought about a more than 10% increase in the efficiency of the RadiPac fans At the same time the noise level dropped by over 3 dB (A). The extra efficiency is converted into higher air flows, in other words the new fans attain higher operating points.
Certified test stand
As a certified manufacturer, ebm-papst fully conforms to the following criteria as specified for test stands by the guidelines of the AHU manufacturers’ association:
“An expert report/test report for fans will be accepted if testing was performed in accordance with the latest standard DIN EN ISO 5801:12-2010 (ISO 5801:2007 incl. corr. 1:2008) by a named test body on a suction-side chamber test rig and the component is manufactured without any modifications.”
Authentic operating conditions
The fans in an air handling unit operate in more or less confined spaces. This leads to a reduction in air performance which has to be taken into consideration when selecting the right fan. At ebm-papst allowance is made for the installation situation.
For comparison measurements, the test fans are fitted in an AHU housing. Use was made of the dimensions 900 x 900 x 760 mm for size 400 fans. For size 560, the dimensions of the AHU housing were 1230 x 1230 x 760 mm. All the fans were centrally mounted in the AHU box.
The corresponding measurements were taken on an officially certified (TÜV) aeroacoustic fan test stand (c.f. text: Certified test stand) which permits the simultaneous recording of air performance data and noise values. This chamber or combination test rig consists of two low-reflection half chambers with high-impedance floor conforming to accuracy class 1 for acoustic measurements. Air performance measurements can be conducted at an air flow of up to 100,000 m³/h with a static pressure increase of up to 3,000 Pa.
The “old” vs. “new” comparison
Comparison with competing products
The ebm-papst RadiPac (green curve) was challenged by:
- A manufacturer who also develops EC external rotor motors (blue) and
- A company which uses corresponding control electronics (red) with PM internal rotor motors (permanent magnet).
The diagram shows air performance, overall efficiency and noise generation. The characteristic curves speak for themselves.
EC motors have not just proven their worth as a means of driving fans and pumps in buildings. More and more fans used for cooling switch cabinets and converters as well as in modern agriculture are being fitted with EC motors offering an unbeatably compact design and extremely quiet operation in addition to outstanding efficiency.
EC motors are very similar to PM motors for example. Both types have a rotor fitted with magnets and the stator carries the excitation winding.
By virtue of their design, EC and PM motors are always superior to the widely used asynchronous motors (AC motors) in terms of efficiency. This particularly applies to applications involving low motor outputs and low speeds.
The efficiency levels currently achieved by the energy-optimised motor, a mains-powered permanently excited synchronous motor (also known as BLDC or PM) are far superior to the values required by efficiency class IE4 (as per IEC 60034-30).
ebm-papst EC motors already contain the necessary control electronics. This offers advantages in the event of EMC problems and the unit only has to be connected to one transfer point.
EC motors have become established as drive units for fans in many areas, not just for use in buildings. The external rotor design is ideal for air handling applications, as the axial or centrifugal fan impeller can be mounted directly on the external rotor.
The term EC motor is often used to refer to different concepts. However, as BLDC, EC and PM all describe motors with extremely similar properties, the name used is of no great significance – the important thing to remember is that: Genuine GreenTech EC motors from ebm-papst are designed to operate without potentially problematic rare-earth magnets.
In the power range below 10 kW, the use of efficient EC motors can reduce power consumption by well in excess of 10%. Savings of 50% and more are possible if this is accompanied by adaptation of the air performance to changing requirements, in other words by the use of speed control. EC motors in particular operate far more efficiently in the part load range than converter-controlled AC motors. Further savings can be achieved by optimising the air routing upstream and downstream of the fan. This is often not possible due to a shortage of space, which is where another outstanding feature of the new RadiPac impellers comes into play: The outflow of air from the impeller is directed in such a way that virtually no loss occurs when it is deflected into the main flow direction in an air handling unit. This illustrates the systematic approach adopted by ebm-papst when developing the new impeller generation.
All-in-all, modification of the flow machine and the motor brought about a more than 8% increase in the efficiency of the RadiPac fans. This can be seen from the difference between the green and black curves.
The full expert report of the ILK in Dresden can be viewed at: www.ebmpapst.com/ilk
You can find more information about the new RadiPac here: www.ebmpapst.com/radipac