More efficient transformer materials

October 1, 2014, Fraunhofer-Gesellschaft
A scientist removing samples of electrical steel from the test facility at Fraunhofer IWS; this type of material is one of the main components of transformers. Credit: Fraunhofer IWS

Almost every electronic device contains a transformer. An important material used in their construction is electrical steel. Researchers have found a way to improve the performance of electrical steel and manufacture it more efficiently, using an optimized laser process.

Transformers convert the standard voltage from the wall outlet into the lower voltages required by electronic devices. Similar but more powerful transformers are used in electricity substations to convert the high voltages of the transmission grid into the standard AC power supply delivered to households. All transformers have the same basic structure: a pair of iron cores, around which wires of different lengths are wrapped. These are the transformer coils, one of which generates an oscillating magnetic field, while the other converts this magnetic field into a voltage. To minimize the associated with this process, special types of iron-silicon alloy known as electrical steel are used to make the core. In their native state, these alloys have a grainoriented structure which determines their .

Grain-oriented means that the material has a crystalline structure in which each crystal or grain is arranged in a regular periodic order. "By heating selected areas of the material, it is possible to reduce the size of the domains with the same magnetic orientation, which in turn alters the magnetic structure of the steel. This results in a lower heat development and thus reduces the material's hysteresis loss," says Dr. Andreas Wetzig, who heads the laser ablation and cutting department at the Fraunhofer Institute for Material and Beam Technology IWS in Dresden, describing the complex changes that take place inside the material. Laser processing has long become established as the preferred method for this type of heat treatment. While the steel sheet, measuring around one meter in width, moves forward at a rate of more than 100 meters per minute, a focused laser beam travels at very high speed (approximately 200 meters per second) from side to side across the surface of the material along paths spaced a few millimeters apart.

Flexible control of the laser beam

The Dresden-based research team has optimized this process: "We have developed a means of deflecting the laser beam that allows the distance between the paths to be controlled flexibly and adapted to different parameters," reports Wetzig. To do so, the researchers make use of galvanometer scanners. These devices consist of galvanometer driven mirrors attached to one end, which is used to deflect the . This increases the flexibility of the machining process and allows it to be adapted to specific conditions, such as the quality of the raw material, and to different production rates. The main aim of this research is to facilitate the integration of laser processing in existing production environments, in order to save time and costs.

In a further effort to reduce hysteresis loss in electrical steel, the researchers have recently started working with a new type of solid-state laser: the fiber laser. "The results we have obtained so far are very promising. This type of laser offers better heat absorption characteristics than traditional CO2 lasers," says Wetzig. It cuts hysteresis loss by up to 15 percent, compared with the 10 percent normally achieved until now. The optimized process is currently being implemented by the first commercial customer.

Possible energy savings of up to 25 percent

The IWS experts are currently working on the next important stage: that of expanding the applications of their technology to electrical steel for engine components. However, unlike transformer steel, these materials do not have a grain-oriented structure and therefore possess different magnetic properties. "This means that we cannot transfer our process one-to-one without modification," explains Wetzig. The benefits of processing in the case of non-grain-oriented electrical steel vary according to the working point of the specific engine or motor. The working point is the point of intersection between the torque curve and rotational speed curve of the drive system and the driven machine. In high-performance machines such as vehicle engines, which are designed to run at high rotational speeds, energy loss can be reduced by a few percentage points. In high-torque electric motors such as those used to operate pumps, the reduction in energy loss can be as high as twentyfive percent.

Explore further: Diamond makes laser beams more brilliant

Related Stories

Diamond makes laser beams more brilliant

May 5, 2014

( —For the first time, researchers have shown that diamond can radically improve the quality of high power laser beams, according to new photonics research published overnight in Laser & Photonics Reviews. A team ...

Researchers design plasmonic cavity-free nanolaser

September 22, 2014

( —A team of researchers at Imperial College in London has designed a new type of laser, one that could be made much smaller than today's models because it would be cavity-free. In their paper published in the ...

Deformable mirror corrects errors

May 14, 2014

Very high power is needed to cut or weld using a laser beam. But this creates its own problem: the beam's energy deforms the mirrors that are focusing it to a point. When this happens, the beam expands and loses intensity. ...

Recommended for you

Team breaks world record for fast, accurate AI training

November 7, 2018

Researchers at Hong Kong Baptist University (HKBU) have partnered with a team from Tencent Machine Learning to create a new technique for training artificial intelligence (AI) machines faster than ever before while maintaining ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.