Energy-savings potential for small axial fans:
Identically sized EC drive replaces shaded-pole motor
In countless fans, shaded-pole motors are the current state of technology, particularly if low power is required. Because these motors can be operated directly on the AC voltage mains, they are frequently preferred for household appliances. One typical application area is fans for convection ovens. However, shaded-pole motors-often known as Q-motors-are also used as an inexpensive standard drive for small axial and centrifugal fans in many refrigeration and air-conditioning technology applications. The asynchronous motor's typical smooth running, maintenance-free performance and long service life have also contributed to the widespread use of this motor type. However, there is also an important disadvantage: because of their design principle, shaded-pole motors work at comparatively low efficiency.
Today, saving energy is more important than ever. Implementing energy-savings in fans is particularly effective, as these are often operated with high duty cycles, for example in refrigerated cases, bottle coolers and underfloor convection heating systems. As a result, high motor efficiency makes a pronounced difference-not only in terms of reducing environmental impact, but also keeping money in the end user's wallet. However, higher efficiencies also mean that less waste heat is given off into the surrounding area. This results in additional energy-savings, as less energy must be generated for the cooling process in the first place.
Consistent further development: from the Q-motor to the iQ-motor
However, finding a suitable alternative to the widespread Q-motors and their low efficiency was not easy. Using the energy-efficient EC technology currently being implemented in other fan applications did not make sense here, due to its relatively high purchase price and the fact that such models are not well suited to the application area. The external rotor motors available in EC technology have limited suitability to applications that require a motor with drive shaft.
Motor and fan specialist ebm-papst Landshut understands this problem. To replace Q-motors, it has developed a new EC motor that is no different on the exterior from the tried-and-tested shaded-pole motors. However, the EC technology on the inside has a significant effect on the efficiency (see text box). This allows immediate energy-savings of up to 70%. At the same time, the integrated electronics provide intelligent open and closed-loop control options that conventional AC technology lacks.
The newly developed product, called the iQ-motor, is mechanically and electrically compatible to the "old" technology, which allows the motors to be easily interchangeable. Likewise, axial impellers with diameters of 154 to 254 mm can be installed on the new iQ-motor. The same holds true for the mounting flange, the wall ring and the guard grille. The mains cable is all that is necessary for the electrical connection. The motors are designed for rated voltages of 115 or 230 V at a power frequency of 50 Hz or 60 Hz. The maximum power output is up to 10 watts.
It pays to switch
Switching over to the new motor technology is worthwhile whenever the old shaded-pole motor fails or energy-savings are desired. The switch pays off for both the environment and the user, as the following example calculation shows: in a small supermarket, 40 fans work that have 200 mm impellers and a 34° incline. The energy savings in this case is 70%, which corresponds to 7.5 MWh per year. For the environment, this value means that 4.4 fewer tonnes of carbon dioxide are produced. However, users profit as well. If we assume an electricity price of 10.7 Eurocents/kWh, they save 800 Euro a year.
Of course, similar savings can also be attained in many other applications. In addition to refrigerated cases and convection ovens, the typical application areas of the new fan generation include cooling compressors, underfloor convection heating systems and all others that require small fans. This also includes industrial areas, such as spinning frames, where they are used to remove dust.