Researchers at TU Graz improve small electric motors

Brushless drives for pumps and ventilation systems work more efficiently and quietly thanks to innovations in design, control and production technology. Users of electrical appliances and the automotive industry can benefit. 3D printing was also used in the process.

Small electric motors can be found in a variety of household appliances, tools and computers as well as in modern cars, where they drive auxiliary units such as pumps and fans. Individually, each of these motors does not consume much energy, but together they offer great potential for savings. The research team of the recently successfully completed ‘CD Laboratory for Brushless Drives for Pump and Fan Applications’, led by Annette Mütze from the Institute of Electric Drives and Power Electronic Systems at TU Graz, has now further tapped into this potential: Thanks to innovative design, modified control technology and the use of new manufacturing techniques, the brushless integrated drives developed here consume less power, operate more quietly and are lighter.

Inclined claws reduce vibrations

Larger claw-pole motors are used in vehicle lighting systems, for example. Their use as small drives is less well known. Annette Mütze’s team has reduced the so-called ‘cogging torques’ of these small drives by bevelling and grooving the claws, which does not incur any additional costs. This reduces the brief engagement of the claws when the motor is turned and thus unwanted vibrations.

“This has enabled us to reduce an important source of noise by 70 per cent. As a result, the drives run much more smoothly and quietly,” says Annette Mütze.

Simplified control reduces switching losses

Efficiency gains are achieved through simplified control of the current flow. Usually, pulse width modulation regulates the current with which the motor of a fan or pump is supplied. In order for the current to flow in the desired rectangular pattern, a large number of switching operations are required, which causes additional energy consumption.

“We only switch our drives on and off once per desired rectangle,” says Annette Mütze. “This has enabled us to significantly reduce the additional energy consumption caused by switching losses.”

Particularly at low currents, these drives therefore have a much better overall efficiency than those that are controlled via conventional pulse width modulation. Due to the drastically reduced number of circuits, the circuit boards of the motors also require half as many capacitors, which reduces costs.

3D printing of ferrite-based material

The third innovation is the realisation of PCB motors with ferrite cores. ‘PCB’ stands for “Printed Circuit Board” and, in the case of the motors, means that the windings that generate the magnetic field required for the drive are designed in the form of printed circuit boards. This allows a high degree of automation in production. Annette Mütze’s team equipped the circuit boards with 3D-printed ferrite cores, thereby improving the guidance of the magnetic flux in the motors. This was the prerequisite for the use of more cost-effective magnets, which are also based on ferrite.

MSG Mechatronic Systems GmbH was involved as a corporate partner in the ‘CD Laboratory for Brushless Drives for Pump and Fan Applications’.