News archive

Sophisticated cooling systems offer commercial benefits too

With the need for greater efficiency, reliability and reduced overall cost of ownership, cooling systems have become more flexible and more sophisticated. Papst's Gareth Jones cites the changes and puts the case for a unique, software based system.

Those were the days when the function of a cooling fan was merely to ensure that the temperature of the host application did not exceed a predetermined level. In other words, simply to cope with the worst possible case scenario.

Little (if any) attention would have been given to the amount of time that the cooling system was 'overworking', i.e. operating at maximum airflow. For so long as everything continued to operate, "what is the problem?" one may well have asked. After all, that which is simplest is best - isn't it?

It is at this point that the 'complexities' and true needs of a cooling system need to be considered. Firstly, there is the question of efficiency. In the ultra competitive environment in which we now operate, designers must find ways of reducing noise and power consumption whilst still delivering the required airflow performance. Clearly, operating a cooling system at 100% fan speed at all times is not efficient!

Equally important to the engineer is the subject of reliability. It is well known that the greatest cause of fan failure is worn bearings. Bearing degradation increases when subjected to heat. Additionally, from an electromechanical viewpoint, the life of components to be cooled can be extended if they are not subjected to wild temperature changes.

The overall cost of ownership of a cooling system should take into account the above factors. Not forgetting, that as well as the cost of replacement fans and maintenance costs, what about the cost and implications of shutting down (or at least running at reduced power) say, a mobile base station or the IT infrastructure of financial institutions etc.

Returning to environmental issues, the noise levels produced by cooling fans is also an important point, and it is obvious that fans operating a full speed will produce higher levels than those running at say, 30% of full speed. This may not seem an important point, but in applications where many racks or trays of cooling fans are deployed, noise can be a big issue. Many manufacturers are required to comply with strict acoustic noise emission legislation for internal and external installations.

It therefore follows that the ability to control the speed of a fan is crucial to obtaining optimum performance from the cooling system and the host equipment.

Early developments
Around twenty years ago, fans became available with a third wire that provided a tacho (speed) signal, thus enabling a basic monitoring function whereby if the speed of the fan was seen to fall, i.e. due to bearing problems, it could be exchanged before a possible failure occurred. Whilst this relatively basic 'system' helped from a maintenance/replacement viewpoint, it did nothing to extend the life of the fan and did not fully address efficiency and noise issues.

The next progression was the development of temperature-controlled fans such as Papst's Variofan. With this system, fan speed could be controlled and varied dependant on the 'feedback' provided by a temperature thermistor that was contained within the fan housing or remotely in the host equipment.

The variofan solution was a huge leap forward in fan control, meaning that a fan need only be run at full speed when it was absolutely necessary. The 'modus operandi' of such a system was that at the lower end of the cooling spectrum - let's say 30°C - the fan would run at half speed, increasing on a linear basis between 30°C and 50°C, and then running at full speed above 50°C. As the fan did not operate continually at maximum speed, mechanical wear was reduced prolonging its useful life, noise emissions were reduced and energy savings could be made as the overall power consumption of the fan was less.

Whilst offering a great improvement in fan control, Papst recognised that the thermistor-controlled system was an analogue, hardware based format that could be vastly improved upon by using digital control executed via a software platform.

Software based
Born from continued innovation and development effort, Papst's new generation of intelligent cooling fans stand on a platform known as Vario-Pro®, a software based fan configuration concept that offers unprecedented levels of control, increased flexibility, greater reliability and improved customer service levels. The technology offers programmed intelligence and customer-specific integrated functions that make cooling electronic components more accurate and importantly for OEMs - more competitive.

Indeed a feature of Vario-Pro® is that it offers significant commercial benefits, not just technical ones, and this has been part of its design ethic from concept through to product launch. Both OEMs and end users need features like quick time to market, flexibility and cost effective cooling solutions.

It's a common occurrence in electronic engineering that cooling systems are frequently amongst the last components in a system to be clearly specified and designed. This leaves little time for the cooling system supplier to engineer the best solution, and of course, deliver it. Vario-Pro®'s reduced time to market helps to reduce the overall delivery time for an electronic system and can even help claw back lost design time. The performance configuration of the fan is software dependent, enabling quick sampling from stock. In fact, it only takes minutes to configure and programme new speed versions for different temperature characteristics. Previously, changing fans that used a PCB based control concept was achieved by making hardware component alterations, whereas Vario-Pro® allows much quicker changes as it is software based.

The central control unit of Vario-Pro® comprises of a microcontroller and an EEPROM which stores all properties. This configuration offers a number of distinct advantages. Based on a selection of current fans, the client receives a tailor made fan per software configuration, offering a wide range of functions and performance. Using Vario-Pro®, any shape of temperature/speed profile within a temperature range of -40°C to 80°C can be programmed into the fan, with up to 14 base points incorporated. These can be step change, or linear interpolation between the points - it is entirely the customers' choice.

Due to the fact that manufacturing is standardised and optimised - there are few 'specials' or component variations - the highest quality standards are maintained acting to raise product reliability even further. A test protocol is available for every fan. There are further benefits; Vario-Pro® is able to integrate new application possibilities such as automatic triggering of emergency signals or the provision of automatic switch-off/warning signals when a device temperature becomes critical.

Motor management
Vario-Pro® scores high in the area of (fan) motor management. The system offers tight tolerances throughout the manufacturing process enabling increased accuracy of operating speed (rpm) throughout the full operating range. Increased efficiency is afforded due to optimum co-ordination of motor hardware and software, and reduced power consumption and operating temperatures are attained due to digital motor management.

To make things really flexible for end users, should the requirements of an application change, larger size Vario-Pro® fans (>135mm2) are re-programmable, so the software can be rapidly revised for optimum performance. Such Papst fans currently available with Vario-Pro® include DV62xx, 64XX, 62XX, 72XX and RG160 types. Other fans will be introduced to incorporate the system as the need dictates. The smaller sizes (<135mm2) of fans with Vario-Pro® are programmable once only, and are delivered with optimum temperature/speed characteristics to suit the application. In this format, Papst fan types 41XX, 42XX, 43XX, 33XX, 83XX, 52XX, DV41XX, DV52XX, RG125 and RG90 will be available.

Due to its digital design, Vario-Pro® offers minimum operating tolerances, drift free performance and long service life, making it the most innovative solution for today's sophisticated design requirements.