The first external rotor EC motors with 20 kW shaft power

If modern EC motors are used as the driving force in fans instead of conven­tional AC tech­nology, energy consump­tion and hence oper­ating costs can be signif­i­cantly reduced. It pays to convert to EC tech­nology for other reasons as well. EC fans have infi­nitely vari­able speed control and operate at high effi­cien­cies even in partial-load oper­a­tion. They also offer networking options and, if appro­pri­ately designed, can with­stand even harsh ambient condi­tions. These advan­tages can now also be used with larger fans that deliver huge air flows. With its new DV280 (Fig. 1) ebm-papst has devel­oped a new high-perfor­mance EC motor that, with an elec­trical input capacity of up to 20 kW shaft power and a torque of impres­sive 180 Nm, is suit­able for universal use on large fans world­wide.

The robust motor is designed for heavy wheel loads, oper­ates with the high effi­ciency of up to 95 percent that is typical of EC motors (better than IE5 in accor­dance with IEC/TS 60034-30-2) and is there­fore an energy-effi­cient alter­na­tive to the powerful AC motors that are commonly used in this area of appli­ca­tion (Fig. 2). The new motor does not require any rare earths for its inte­grated perma­nent magnets and is also very compact due to the external rotor design typical of ebm-papst, while at the same time being well protected against envi­ron­mental influ­ences thanks to its robust construc­tion.

Fewer wearing parts, compact design and many func­tions

As a direct drive, the EC motor offers many advan­tages in prac­tical use. For example, no wear-prone and high-main­te­nance belt trans­mis­sions are neces­sary. The fan impeller, which can be either centrifugal or axial, can be mounted directly on the robust stub shaft or motor rotor flange. As the complete control elec­tronics (Fig. 3) are inte­grated in the motor, there is no need for external devices such as vari­able frequency drives that have to be assem­bled, wired and para­me­ter­ized. The elec­tronics of the EC motors can be replaced for possible main­te­nance work without having to disas­semble the motor or fan. The elec­trical inter­faces are program­mable, which reduces the number of connec­tion termi­nals required and hence the wiring work.

But the new motor also has plenty to offer in other respects. For example, a vibra­tion sensor is inte­grated, which enables auto­matic reso­nance detec­tion and ulti­mately increases oper­a­tional reli­a­bility. This is because prema­ture fan fail­ures are usually caused by vibra­tions due to the instal­la­tion situ­a­tion. To detect these, a test start-up is carried out during commis­sioning in which the vibra­tion level is recorded and analyzed over the entire speed curve. If exces­sive vibra­tion veloc­i­ties are now detected in certain ranges, the control soft­ware in the elec­tronics auto­mat­i­cally adjusts itself so that these speed ranges are “hidden” during further oper­a­tion. This means that they are passed through, but there is no contin­uous oper­a­tion in these ranges.

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. 4). 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.

If an imbal­ance occurs during oper­a­tion, for example due to cont­a­m­i­na­tion, this is also detected and displayed at a suit­able point so that appro­priate reme­dial measures can be initi­ated. Oper­a­tors can manu­ally edit the soft­ware settings at any time and always have full control. The motor’s heat dissi­pa­tion has also been opti­mized. Reli­able cooling is provided both by the special housing geom­etry (Fig. 5) and an addi­tional fan, which actively cools the elec­tronics during oper­a­tion.

Complete plug & play solu­tion

Thanks to its external rotor design, the motor also has impres­sively compact dimen­sions. This means that the entire fan unit requires less space, making trans­port and assembly of the complete plug & play solu­tion much easier. This is partic­u­larly bene­fi­cial when ebm-papst combines the new motors with back­ward-curved centrifugal impellers (Fig. 6). These are attached directly to the outer rotor, with the motor immersed in the impeller.

As a result, the fan requires little space in the axial direc­tion. Even large, size 800 RadiPac centrifugal fans that convey air at up to 40,000 m³/h wide open and reach maximum pres­sures of 2,300 Pa, fit through normal doors in retrofit projects, for example, and do not have to be deliv­ered by crane. The plug & play fan systems arrive at the construc­tion site with perfectly coor­di­nated motor, elec­tronics and fan tech­nology as fully assem­bled, compact units – which makes handling and commis­sioning child’s play.

The special blade geom­etry of the RadiPac product range dras­ti­cally reduces flow losses. The inlet ring made of galva­nized sheet steel is designed for perfect inter­ac­tion with the new impeller. The sophis­ti­cated impeller geom­etry not only reduces flow losses, but also noise gener­a­tion. In addi­tion, its robust mechan­ical design means that the impeller has an impres­sively long service life.

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“High perfor­mance for large fans”

The DV280 is the most powerful of the fan drives provided by ebm-papst. Rainer Müller, respon­sible for the engines mechanics, presents the new power­house.

Which appli­ca­tions did you have in mind when devel­oping the DV280?

Specif­i­cally appli­ca­tions involving venti­lation tech­nology, cooling towers, or process cooling where large fans with impellers of up to two meters in diam­eter are required. These appli­ca­tions often still use AC motors in combi­na­tion with vari­able frequency drives, trans­mis­sions, or belt drives.

The new, robust DV280 delivers a high torque of 180 Newton meters at an elec­trical input capacity of up to 20 kW shaft power, making it suit­able for universal use on large fans.

Does such a large unit not also use a lot of power?

No, quite the oppo­site! Thanks to the state-of-the-art EC motor, the energy consump­tion and oper­ating costs can be signif­i­cantly reduced with the DV280. That aspect is becoming increas­ingly impor­tant for oper­a­tors. When the next stage of the Ecode­sign Regu­la­tion for fans comes into force, if not before, many fans that are powered by an AC motor will no longer meet the minimum require­ments for effi­ciency. When that happens, the right drive solu­tion will be a high-perfor­mance EC external rotor motor that oper­ates at high effi­ciency levels. In addi­tion, EC fans are infi­nitely adjustable and work extremely effi­ciently even in partial-load oper­a­tion.

Thanks to the state-of-the-art EC motor, the energy consump­tion and oper­ating costs can be signif­i­cantly reduced with the DV280.

Replacing such large fans is often a problem because of the lack of space. Is it the same here?

We use an external rotor motor design, which allows for a much more compact unit than conven­tional internal rotor motors. This means that the entire fan unit requires less space, making trans­porta­tion and instal­la­tion much easier. For example, when combined with one of our centrifugal impellers, the motor is immersed in the impeller because it is mounted directly on the external rotor. Even large RadiPac fans in size 800 there­fore easily fit through normal doors. These compact plug-and-play units are deliv­ered fully assem­bled to the construc­tion site and are easy to install.

Why is the inte­grated reso­nance detec­tion func­tion so impor­tant?

Fan fail­ures are often caused by vibra­tions gener­ated due to the instal­la­tion condi­tions. By detecting this at an early stage, we can signif­i­cantly improve oper­a­tional reli­a­bility. That is why we have inte­grated a vibra­tion sensor. During commis­sioning, our customers perform a test start-up during which the vibra­tion levels over the entire speed curve are analyzed. If exces­sive vibra­tion veloc­i­ties are detected, the control soft­ware auto­mat­i­cally avoids these speed ranges during oper­a­tion.