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New ways to stay cool

Intelligent cooling solutions improve efficiency in power- sensitive devices. So just what should the intelligent buyer know about heat-removal products? RS Components'Michael Burns provides some answers

Electronics purchasers play an important role in the efficient use of energy; helping to shape the way energy is created, distributed, consumed and controlled. That position holds greater responsibility today as we become increasingly aware of the importance of energy conservation.

At the semiconductor level, manufacturers are developing

ultra low-power processes that operate more efficiently, but even in an ultra low-power process, heat builds up and if it isn’t dissipated the transistor fails. As the density and operating frequency of transistors continues to rise, it is important to consider these effects and implement efficient heat removal. The problem becomes more prevalent in power devices, which must deliver power more efficiently in ever-smaller devices.

Unfortunately, heat removal uses power, which is leading to

EBM-Papst's ACMaxx is a powerful, yet compact EC fan

new thinking from vendors, who are taking a ‘just enough is good enough’ approach. This allows demand to set the level of cooling. Prior to this development, AC fans had just two states: on or off.When the system was on, the fan would also be on, operating at full speed. There are now many alternatives to these simple AC fans, however, which use various levels of control to allow their operation to be modified depending

on the conditions. This not only helps to increase the reliability and extend the lifetime of the fan, but also delivers significant energy savings, as well as the added benefit of lowering the overall acoustic noise of the system.

take control

The first significant step in this evolution was the development of electronically commutated (EC) fans. This is now the predominant technology because of the performance benefits it offers over induction motors. In particular EC technology overcomes the losses associated with magnetic induction, but in addition it affords a greater level of control over the fan’s operation.

The technique normally takes the form of a brushless DC

(BLDC) motor. Although this requires additional circuitry compared to an induction motor, this can be integrated into the motor’s housing, giving rise to more powerful yet compact EC fans. EBM-Papst's ACMaxx range provides a typical example.

This family of fans is powered from a normal AC supply which is rectified by the on-board controller and used to operate

the brushless DC fan. Its power efficiency and ‘new for old’ form factor means that the fan’s output can be increased without further modification or need for greater input power.

Adding an internal or external negative temperature p26 December 2010 | 25

Pfannenberg’s FLZ 600 hygrostats modify fan behaviour according to temperature and relative humidity

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