Electric motor industry gains momentum due to new water cooling system

Lappeenranta University of Technology (LUT) has developed a new motor solution able to produce greater torque without a gearbox. In addition, the motor is compiled of steel blocks reminiscent of Legos, and it is cooled with water. The solution is less costly and more reliable than current motors.

Researchers and product development engineers have long reflected on what electric drives could be like. In the solution most frequently used at the moment, the shaft is connected to the gearbox, which lowers the rotation speed. The disadvantages of this model are problems related to the reliability of the gearbox and the high cost of the system.

In contrast, the motor developed by LUT operates without a gearbox. However, the absence of the gearbox would traditionally increase the size of the motor.

The dimensions of the motor can be kept reasonable by choosing the right cooling method. LUT's motor is cooled with water, not air, which traditional motors use. The direct liquid cooling is introduced into the windings.

Combining water and electricity might seem like a bad idea, but the researchers emphasise it has clear advantages compared to current models. Water cooling enables improving the power production capacity of a permanent magnet motor, thus reducing the size of the motor. Moreover, the motor is completely safe.

"Water cooling poses no problems. It is applied in many devices today, including combustion engines. The water pipes have no joints. The joints are situated on the outside of the motor. If they leak, they will not leak into the motor and therefore the water poses no risk," explains Professor Aki Mikkola, who was involved in developing the motor.

The second special feature of the motor is that its rotor structure is built from "Lego blocks": steel sheets with spring attachments. This method enables building large and durable structures without welding large sheets together. As a result, fatigue issues related to welded joints can be avoided and the manufacturing process of the motor simplified.

Surprisingly, the Lego-like structure was originally not meant to be the final solution.

"We stumbled on its advantages by accident. We originally meant to use it only in the miniature model. Since miniatures are difficult to weld, we opted for a different sheet structure. When the model was finished, we noticed some unexpected advantages in its operation compared to our computational models."

The unexpected advantage was extensive mechanical damping. In other words, the model suppresses vibrations in the structure. Consequently, the motor operates steadily and does not suffer from fatigue failure. 

At the moment, a new electrical machine architecture is being developed in the Tekes-funded project New knowledge and business from research ideas. The project explores the commercial possibilities of technologies. Potential applications already identified include mixers, crushers, wind turbines and the shipbuilding industry.

Further information

Aki Mikkola, Professor, +358 40 736 3095, aki.mikkola@lut.fi

Scott Semken, Post-doctoral Researcher, +358 50 569 5713, scott.semken@lut.fi