Design & Technology / Product
Forte LPI Hybrid Development Story – The Electric Motor September 2nd, 2009
By Kim, Wan Seung
R&D Strategy team
The electric motor is a core element that provides secondary driving power to the engine while accelerating and acts as the generator which charges the lithium ion battery with electric energy created when the vehicle decelerates. The soft-type hybrid motor of the Forte LPi Hybrid was designed by Kia and developed in Korea. The Idle Stop & Go (ISG) function realizes outstanding fuel economy and efficiency as it automatically turns off the engine when the vehicle has stopped and turns it back on when accelerating.
The road to developing such a driving motor was bumpy and full of challenges, especially in the beginning. The biggest problem was when the permanent magnet inside the motor kept losing its magnetism. This occurs when there is significant flow of electric current or intense heat. To overcome the problem, developers had to rethink the design and even the material of the magnet. But they managed to improve the design and correct the problem. Analysis and principle tests were conducted to enhance the magnet’s design. They then faced the next hurdle, the durability test.
Researchers had no idea what to expect in the durability test as this was the first development attempt. All of the members of the motor development group decided to monitor the durability test from the beginning to the end. Day and night, and even through the weekends, groups of developers kept vigil by the durability test over a two-month period. When the test ended with success, everyone shouted with joy!
The next, and final test, was noise. Just as a conventional vehicle produces engine noise, the electric motor also creates noise when activated.
The sound is similar to that heard in subways. In particular, noise levels went up at around the 3,000rpm stage. The vehicle assessment team sent a request asking developers to solve this problem as it was a sound that does not occur in existing vehicles. Thus work began to reduce motor noise levels. Developers adopted a fundamental approach to the cause of the noise and took almost a year in changing the design, making samples and conducting tests before they were able to reduce the noise to a level that was imperceptible to customers.
This is the story of how we created an electric motor with our own hands.
The motor inside Forte LPi Hybrid has a maximum power of 15.5kW, maximum torque of 107.8Nm and system efficiency of 92%. This is an improvement of 30%, 13% and 5% respectively compared to the imported motor used in the Pride (Rio) Hybrid since 2005. In particular, our motor outperforms HEV motors of our competitors by up to 7% in maximum power, torque and system efficiency.
※ Editor’s Note: You can read the previous post here: http://kia-buzz.com/?p=2313