© Photo | ebm-papst, KD Busch

The racing machine

Every cubic centimetre of space that is taken up by a fan in server racks or telecom­mu­ni­ca­tion base stations is wasted space. A new gener­a­tion of high-perfor­mance fans gets moving — to make more room

It takes five millisec­onds for the blade to complete one round. The tip cuts through the air at a speed of 210 kilo­me­tres per hour. The high-perfor­mance fan is called the S-Force, and it runs almost twice as fast as others its size. It uses some­thing known as Moore’s Law. In doing so, it regains some­thing extremely precious: instal­la­tion space. At least every two years, the computing power of computer and memory chips doubles. This was predicted by Intel co-founder Gordon Moore back in 1965. Back then, chips were almost big enough to be cooled by placing one’s hand on them, main­frames filled ball­rooms and the small room required for the climate control system was rela­tively unim­por­tant. To this day, Moore has been proven right. Today, chip manu­fac­turers pack the “ball­rooms” into a couple of square centime­tres of silicon, which, when uncooled, reaches the temper­a­ture of a hotplate at the highest setting. To prevent this, the cooling systems are becoming propor­tion­ately more complex. For example, the base station that belongs to each antenna mast in the wire­less network is often no larger than the rolling drawer unit under an office desk. Inside, it is tightly packed with inter­change­able IT modules. However, between ten and twenty percent of the space is reserved for the venti­la­tion system and air circu­la­tion. The exact amount depends primarily on its maximum effi­ciency.

With the S-Force, ebm-papst’s engi­neers have followed Moore’s philos­ophy: pack more power into the same space. In this case, it means a massive increase in speed. This can be attained only with a special fan. The aero­dy­namics of a fan is tuned to a defined speed range. Anything over a certain point only causes turbu­lence of the air. The running power does not convert into the volu­metric flow rate, and the fan “gasps”, so to speak. More­over, the energy consump­tion and mechan­ical loads increase dispro­por­tion­ately. The mate­rial fatigues, the bear­ings over­heat. A device that only rotates faster will not attain a long service life. The S-Force fan in the middle of the five speeds, however, reaches 11,000 rpm. In doing so, it pushes 570 cubic metres per hour of fresh air through its housing?— approx­i­mately the amount of air in a four-room apart­ment in an old building with high ceil­ings. Its output is three times that of a normal fan of this size, and it main­tains this air flow for a good 60,000 oper­ating hours, during which it moves 34 million cubic metres of air.

Multi­plying the output in the same instal­la­tion
space was the goal of Thomas Brodbek, Sales and Marketing Manager

To give the fan the neces­sary endurance, its creators have designed it from the begin­ning for maximum perfor­mance. Instead of the usual single-phase motor, it has a three-phase motor, rare earth magnets in a resin bond, a twelve-pin rather than a four-pin magne­tised rotor, and a robust rotor bearing with ball bear­ings and special lubri­cants. This means a perfor­mance increase of about 500 percent compared to similar motor sizes. The motor elec­tronics of the control­lable, sensor­less EC motor received new inte­grated circuits, which, along with all of the other measures taken, increase the motor effi­ciency up to 85 percent. Effi­ciency of 65?–?70 percent is common. The sickle-shaped blades were given “winglets” on the tips to prevent vortex gener­a­tion?— which not only causes noise, it also brakes the impeller. As another safe­guard against vibra­tions, eight fixed links, rather than the usual three rein­force the housing. These not only strengthen the design, they also lower the noise level while actu­ally increasing the blower output. So that this marathon runner does not over­heat at its fast pace, the devel­opers also refined the air conduc­tion through the motor. This keeps the bearing and motor at temper­a­tures conducive to a long service life, even at full speed.Thus equipped, the example fan can run 39 billion rounds before passing on the baton. However, the owner of the telecom­mu­ni­ca­tions container is inter­ested in some­thing completely different: how much space will be gained? The answer: at the given output, approx­i­mately half the space taken up by cooling with stan­dard fans. With the given space, what is gained is the assur­ance of being able to last through the next Moore cycle, when even hotter chips move in.

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